The authors wish to acknowledge the competitive faculty-initiated collaboration (FIC) grant from KAUST.

1. Preparação de Pré-dopado SrTiO 3 Pó <ol><li> A fim de preparar 10 g de Sr 0,95 Pr 0,05 TiO 3 em pó, pesar as quantidades estequiométricas de SrCO 3 em pó (7,53407 g), TiO 2 nanopowder (4,28983 g), e Pr 2 O 3 protuberância sinterizado (0,44299 g) a seguir à reacção para X = 0,05: </li></ol><img alt="Equação 1" fo:content-width="5in" src="/files/ftp_upload/52869/52869eq1.JPG" width="550" /><ol start="2"><li> Triture os pesados ​​Pr 2 O 3 caroços sinterizados a partículas finas utilizando um almofariz e pilão de ágata. </li><li> Adicionar o pesava SrCO3 pó e de TiO 2 nanopowder ao Pr 2 O 3 e continuar moagem e mistura utilizando um almofariz de ágata e pilão até um pó visualmente homogénea é conseguido. </li><li> Carregar o pó moído em um frasco de vidro e mistura utilizando um dispositivo de turbulência durante 30 minutos para homogeneizar the mistura. </li><li> Carregar o pó misturado resultante num cuidadosamente limpos e polidos de aço inoxidável fieira (1 polegada de diâmetro) e que sanduíche entre dois êmbolos de aço inoxidável. </li><li> Imprensa fria o pó usando uma prensa sob uma carga de aproximadamente 1 tonelada métrica. </li><li> Ejetar o pellet prensado a frio, colocando a matriz em um cilindro de aço inoxidável oco e empurrando os êmbolos e a pelota para fora do topo usando uma haste de empurrar. Após a ejecção do pelete prensado a frio (corpo verde) a partir da matriz, limpar qualquer contaminação na superfície circunferencial do pelete, cobrindo suavemente o sedimento com um pequeno pedaço de fita adesiva e, a remoção de uma camada fina por rasgar a fita. </li><li> Coloque o pellet verticalmente em um barco de alumina preenchido com comprada comercialmente SrTiO 3 em pó como a barreira entre o barco alumina ea imprensa pelota frio. </li><li> Inserir o barco num forno tubular, aquecer até 1300 ° C em 3 horas e mantê-lo a esta temperatura durante 15h. Permitir que o sedimento de arrefecer até à temperatura ambiente no interior do forno quando a calcinação acabou. Este passo é referido como o &quot;processo de calcinação&quot; posteriormente. </li><li> Moer o pellet usando o almofariz de ágata e pilão e carregar o pó resultante em um frasco de vidro para posterior mistura usando a turbulência. </li><li> Carregar o pó para dentro da matriz de aço inoxidável e prensado a frio sob uma cerca de 3 toneladas métricas de carga. </li><li> Repetir o passo de 1,9 mais uma vez a 1400 ° C em 3 horas e guarda-se a esta temperatura durante 20 horas. </li><li> Moer o pellet usando o almofariz de ágata e pilão. </li><li> Repita os passos 1.11, 1.12, 1.13 e mais uma vez para a reacção em estado sólido para atingir a conclusão. </li></ol> 2. Preparação de massa policristalino Pr-dopado SrTiO 3 Ceramic <ol><li> Pesar 1,6 g de pó de AS-preparada (para um disco de 2 mm de espessura e 12,7 mm de diâmetro). </li><li> Prepare pedaços graphoil circulares para cobrir a parte superior e inferior interface dos êmbolos de pó de grafite e colada no grafite morrer. Além disso, uma outra parte preparar graphoil rectangular para cobrir a parede interna do molde de grafite. </li><li> Carregar o pó como preparada num molde de grafite (12.7 mm de diâmetro interno) e o pó de sanduíche entre dois êmbolos de grafite do mesmo tamanho. Perfurar um furo de 2 mm no meio do comprimento da matriz de grafite e a partir da superfície exterior da matriz de cerca de 2 mm da superfície interna para a leitura de temperatura. Nota: Ajustar o comprimento dos êmbolos de grafite que fiquem fora do molde e posicionar o centro do cilindro de pó ensanduichada em que o orifício é colocado para obter uma leitura precisa da temperatura. Os rostos dos êmbolos de grafite precisam ser meticulosamente nivelada durante a usinagem das peças. Qualquer desalinhamento pode resultar na quebra da pastilha sinterizada durante a sinterização plasma pulsado. </li><li> Cold-prima suavemente o pó (carga &lt;200 kg) utilizando uma prensa antes da montagem sobre a centelhaplaca de sinterização plasma no interior da câmara. Use planas polidas placas de suporte de aço inoxidável entre a parte superior e inferior e êmbolos do palco imprensa para evitar danificar os êmbolos de grafite. </li><li> Enrole um pedaço de feltro de grafite em torno da matriz para o isolamento e prenda-o com fios de grafite. Conceber uma janela sobre o feltro de grafite pelo corte de uma peça rectangular de feltro onde a leitura da temperatura orifício é colocado sobre o molde. </li><li> Coloque o molde de grafite e êmbolos carregados na câmara de sinterização plasma pulsado. Mover o palco para a posição final. </li><li> Concentre-se e alinhar o círculo alvo Pyrometer no buraco leitura da temperatura do molde. Verifique se a configuração emissividade do pirômetro está definido para grafite. </li><li> Feche a câmara e colocar uma carga de 7,7 kN (aproximadamente 60 MPa) sobre a amostra. Vácuo e purgar a câmara com Ar três vezes e saem da câmara sob vácuo dinâmico de 6 Pa. </li><li> Aumentar a temperatura, aumentando a corrente (manualmente ou utilizando umprograma). Use 250 A min -1 (correspondendo a aproximadamente 300-400 ° C min-1) para as amostras optimizados. Este é o passo mais importante no processo de sinterização plasma pulsado. </li><li> Manter a temperatura a 1500 ° C durante 5 min, ajustando manualmente a corrente ou utilizando o programa. No final do período de detenção de 5 min, fechou a atual off e solte rapidamente a carga de 7,7 kN para evitar rachaduras da amostra durante o arrefecimento. Deixe o fresco de exemplo para RT no interior da câmara. </li><li> Solte o pellet granel do grafite morrer suavemente com a imprensa fria. Isto é feito colocando o molde de grafite em um cilindro de aço oca e ejectar o sedimento e os êmbolos de grafite utilizando uma vareta de aço que empurra a partir do topo. </li><li> Remover o graphoil nas faces superior e inferior do sedimento, bem como a superfície circunferencial usando uma lâmina afiada. </li><li> Polir a amostra usando um papel áspero areia (400 grade) para baixo para 0,3-0,5 mm de cada lado para garantira remoção completa do graphoil. Limpar a amostra com acetona. </li></ol> 3. Caracterização de eletrônicos e Transporte Thermal Ceramics Propriedades de massa <ol><li> Determinar a densidade do disco cerâmico, ρ, utilizando o método de Arquimedes. </li><li> Medir o peso da amostra, W seco, e então o peso da amostra submersa em água, W molhado, em um sistema de medição de densidade estabilizada e calcular a densidade a partir de Arquimedes </li></ol><img alt="Equação 2" fo:content-width="2.1in" src="/files/ftp_upload/52869/52869eq2.JPG" width="260" /> onde a água ρ é a densidade da água à temperatura de medição (por exemplo, igual a 1 g cm -3 a 300 K). 14 <ol start="2"><li> Medir a difusividade térmica da amostra, d, usando a técnica de inflamação do laser transiente sob uma 75 ml min -1 fluxo de Ar. Medir a espessurada amostra, G, com precisão primeiro usando um micrómetro digital. Nota: As amostras Paralelo-confrontados com diferentes tamanhos e formas (por exemplo, discos redondos 12,7 milímetros de diâmetro ou quadrada 10 x 10 mm 2 discos) e espessuras entre 0,5 e 5 mm pode ser facilmente medido. <ol><li> Na técnica de inflamação do laser difusividade térmica, irradiação de uma face da amostra por um curto (~ 1 mseg) pulso de laser e registar o aumento de temperatura na face oposta por um detector de infra-vermelhos. Em seguida, calcular difusividade térmica pelo software de interface de inflamação do laser a partir da espessura da amostra e o perfil de subida de temperatura-tempo utilizando a equação 15 Parker </li></ol></li></ol><img alt="Equação 3" fo:content-width="1.9in" src="/files/ftp_upload/52869/52869eq3.JPG" width="220" /> em que L representa a espessura do disco e t 1/2 representa a meia-altura da elevação máxima de temperatura do outro side da amostra. Nota: O modelo de 15 Parker assume condições ideais de amostra adiabatic e aquecimento de pulso instantânea, outros modelos têm sido propostos ao longo dos anos, que representam várias perdas na medição, como as perdas de calor, duração de pulso finito, aquecimento de pulso não uniforme e não homogénea estruturas. Temos utilizado o modelo Cowan 16 com correção de pulso, que é um dos métodos mais avançados. Deve notar-se que, a fim de maximizar a quantidade de energia térmica transmitida a partir da superfície frontal e para maximizar o sinal observado pelo detector de IR, as superfícies das amostras deve ser altamente emissiva. Normalmente, isto requer a aplicação de uma fina camada de grafite para as superfícies das amostras. Uma incerteza de 2% -5% na medição da difusividade térmica existe, provenientes da determinação da dimensão. 17 <ol start="3"><li> Cortar o sedimento utilizando uma serra de disco de diamantes em barras rectangulares, 2 x 2 x 103 mm, a condutividade eléctrica e medições de coeficiente de Seebeck, bem como um disco de quadrado, de 4 x 4 x 1,5 mm3 para o calor específico de alta temperatura e uma peça rectangular fina, 8 x 5 x 1 mm3 para medidas Hall. </li><li> Medir o calor específico, C p, da amostra sobre a peça quadrada plana e polida-espelho (4 x 4 x 1,5 mm3) utilizando uma calorimetria de varrimento diferencial (DSC) sob fluxo de árgon. 18 <ol><li> Usar uma taxa de aquecimento de 5 K min -1-se a 40 ° C durante uma preensão isotérmica durante 10 min para permitir que a amostra atingir o equilíbrio térmico, seguido por 20 K min -1 taxa de aquecimento até 500 ° C, com uma taxa de arrefecimento exacta que se seguiu. Executar a medição sob o fluxo de árgon (50 ml min -1 é sugerido). </li></ol></li></ol> Nota: devido à sensibilidade do método utilizado para a análise, conduzir três medições para determinar a capacidade de calor<html> incluindo (1) uma medição de linha de base para subtrair o fundo, (2) a medição do calor específico de um material padrão (tais como safira) com um conhecido C P, e (3) medição do calor específico da amostra. Certifique-se de que as amostras são planas e, a fim de fazer um contacto ideal, com o fundo do cadinho de medição (panelas de Pt / Rh com Al 2 O 3 cadinhos utilizados neste trabalho) polido-espelho. Mais detalhes sobre a estrutura exacta da fase de DSC, uma comparação das técnicas de DSC para os outros, e instruções precisas para a medição de uma amostra pode ser encontrada em várias fontes 19. <ol start="5"><li> Calcular a condutividade térmica a alta temperatura, κ, da amostra a partir dos valores medidos de difusividade térmica, d, o calor específico, C P, e a densidade, utilizando 20 ρ </li></ol>/52869/52869eq4.JPG &quot;Width =&quot; 200 &quot;/&gt; <ol start="6"><li> Placa de ouro sondas aos pontos de contacto (4) sobre a contactos 2 x 2 x 10 mm de 3 peças cortadas a partir da amostra para aliviar os problemas de resistência de contacto. <ol><li> A fim de pulverização catódica ouro apenas nas áreas de contato desejados, enrole uma scotch-fita ao redor da amostra 2 x 2 x 10 mm 3 para usar como um estêncil. Deixe a 2 x 2 milímetros dois rostos un-coberto. Usando uma lâmina de barbear, cortar dois orifícios muito pequenos (aproximadamente 1 mm de diâmetro) no centro da face 2 x 10 mm 2, ao longo de uma linha separada pela distância sondas. </li><li> 21 por pulverização catódica, uma película de ouro ~ 200 nm de espessura usando uma unidade de pulverização de ouro de bancada. </li></ol></li><li> Medem-se as propriedades de transporte eléctrico, ou seja, a condutibilidade eléctrica e de coeficiente de Seebeck) da amostra, como uma função de temperatura 22,23. <ol><li> Medir a condutividade eléctrica através do método de quatro terminais. Medir o coeficiente de Seebeck com a same configuração usando as medições de temperatura e de tensão através dos dois termopar média &quot;sondas&quot;. Meça a distância entre estas duas sondas que utilizam um microscópio digital. Mais detalhes sobre as medidas de transporte elétricas podem ser encontradas em outros lugares 22,23. </li></ol></li><li> 24 medir a concentração de portadores Hall como uma função da temperatura sobre a 8 x 5 x 1 mm3 amostra usando um sistema de medição de propriedades físicas. </li></ol>

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Lett. 87, 092108 (2005).</li><li>Kovalevsky, A., Yaremchenko, A., Populoh, S., Weidenkaff, A., Frade, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhancement+of+Thermoelectric+Performance+in+Strontium+Titanate+by+Praseodymium+Substitution.">Enhancement of Thermoelectric Performance in Strontium Titanate by Praseodymium Substitution.</a> J. Appl. Phys. 113, 053704 (2013).</li><li>Kovalevsky, A. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+a+High+Thermoelectric+Performance+in+Rare-Earth+Substituted+SrTiO3:+Effects+Provided+by+Strongly-Reducing+Sintering+Conditions.">Towards a High Thermoelectric Performance in Rare-Earth Substituted SrTiO3: Effects Provided by Strongly-Reducing Sintering Conditions.</a> Phys. Chem. 16, 26946 (2014).</li><li>Dawson, J. A., Tanaka, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Local+Structure+and+Energetics+of+Pr-+and+La-Doped+SrTiO3+Grain+Boundaries+and+the+Influence+on+Core–Shell+Structure+Formation.">Local Structure and Energetics of Pr- and La-Doped SrTiO3 Grain Boundaries and the Influence on Core–Shell Structure Formation.</a> J. Phys. Chem. C. 118, 25765-25778 (2014).</li><li>Mehdizadeh Dehkordi, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+Insights+on+the+Synthesis+and+Electronic+Transport+in+Bulk+Polycrystalline+Pr-doped+SrTiO3&#8722;&#948;.">New Insights on the Synthesis and Electronic Transport in Bulk Polycrystalline Pr-doped SrTiO3&#8722;&#948;.</a> Appl. Phys. Lett. 117, 055102 (2015).</li></ol>

The authors have nothing to disclose.

Neste protocolo, apresentamos os passos da estratégia de síntese, a fim de preparar com êxito policristalinos granel dopado-PR SrTiO 3 cerâmica apresentando melhores propriedades eletrônicas e termoelétricas. As principais etapas do protocolo incluem (i) a síntese em estado sólido do dopado SrTiO 3 em pó em ar sob pressão atmosférica e (ii) aproveitando as capacidades de técnica de sinterização plasma pulsado para densificar o pó preparado como em alta densidade de massa cerâmica e ...

Thermoelectrics óxido foram mostrados para ser candidatos promissores para aplicações termelétricas de alta temperatura, de estabilidade e de custo perspectivas para propriedades de transporte eletrônico. Entre as termelétricas de óxido do tipo n, altamente dopado titanato de estrôncio (STO) tem atraído muita atenção devido às suas intrigantes propriedades eletrônicas. No entanto, uma grande condutividade térmica total (κ ~ 12 W K -1 m -1 a 300 K para cristais individuais) 1 e uma baixa mobilidade do transportador (μ ~ 6 centímetros 2 V 1 s-1 a 300 K para cristais individuais) 1 afectar prejudicialmente o desempenho termoeléctrico que é avaliado por uma figura de mérito adimensional, ZT = α 2 σT / κ, onde α é o coeficiente de Seebeck, σ a condutividade eléctrica, T a temperatura absoluta em graus Kelvin, e κ a condutividade térmica total. Nós aqui definir o numerador como o fator de potência, PF = α 263; T. A fim de que este material termoeléctrico óxido de competir com outros thermoelectrics de alta temperatura (tais como ligas de SiGe), são requeridos um aumento mais pronunciado no factor de potência e / ou diminuição da condutividade térmica da estrutura. A maioria dos estudos experimentais, a fim de melhorar as propriedades termoeléctricas de STO têm-se centrado principalmente na redução da condutividade térmica através estirpe de campo e espalhamento flutuação massa de fonões. Estas tentativas incluem: (i) simples ou duplas de doping do Sr 2+ e / ou Ti 4+ locais, como os principais esforços no que diz respeito a esta direção, 2,3 (ii) Síntese de superrede naturais estruturas Ruddlesden-Popper a fim de reduzir ainda mais a conductividade térmica através de camadas isolantes SRO, 4 e (iii) de engenharia composto por adição de uma segunda fase de nanoparticulado. 5 No entanto, até recentemente, nenhuma estratégia de reforço tem sido relatada a substantially aumentar o fator de energia termelétrica nestes óxidos. Os valores do fator de potência máxima registada (PF) em única massa e STO poli-cristalino foram confinados a um limite máximo de PF &lt;1,0 W m -1 K -1. Uma variedade de abordagens de síntese e técnicas de processamento têm sido utilizados para implementar as ideias tentativas acima. As rotas de síntese pó incluem reação de estado sólido convencional, 6 sol-gel, 7 hidrotermal, 8 e síntese de combustão, enquanto que 9 sinterização convencional, 6 prensagem a quente 10 e recentemente sinterização plasma faísca 12 estão entre as técnicas comuns usadas para densificar as pós em massa cerâmica. No entanto, para um dopante semelhante (por exemplo, La) e a concentração de dopante, os massa cerâmica resultantes exibem uma gama de propriedades de transporte electrónicos e térmicas. Isto é, em grande devido à química defeito fortemente dependente do processo de SrTiO &lt;sub&gt; 3, que resulta em propriedades dependentes de síntese. Há apenas um punhado de relatórios otimizando os parâmetros de síntese e processamento de beneficiar transporte termelétrica. Vale ressaltar que, devido ao muito pequeno phonon livre percurso médio em SrTiO 3 (l ph ~ 2 nm a 300 K), 11 nanoestruturação não é uma opção viável para a melhoria do desempenho TE de cerâmica grandes quantidades STO principalmente através da redução da condutividade térmica da estrutura. Recentemente, nós relataram melhora mais de 30% na termelétrica figura de mérito em não uniforme Pr-dopados SrTiO 3 cerâmica provenientes de um fator de potência termelétrica reforçada simultaneamente e condutividade térmica reduzida 12,13. Neste protocolo de vídeo detalhado, apresentamos e discutir os passos de nossa estratégia de síntese para a preparação destes Pr-dopado cerâmica STO que exibem melhores propriedades electrónicas e termoeléctricos.

<table><tbody><tr><td>SrCO&lt;sub&gt;3&lt;/sub&gt; Powder, 99.9%</td><td>Sigma Aldrich</td><td>472018</td><td></td></tr><tr><td>TiO&lt;sub&gt;2&lt;/sub&gt; Nanopowder, 99.5%</td><td>Sigma Aldrich</td><td>718467</td><td></td></tr><tr><td>Pr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Sintered Lumps, 99.9%</td><td>Alfa Aesar</td><td>35663&amp;nbsp;</td><td></td></tr><tr><td>Spark Plasma Sintering&amp;nbsp;</td><td>Dr. Sinter Lab</td><td>SPS-515S</td><td></td></tr><tr><td>Resistivity/Seebeck Coefficient Measurement System</td><td>Ulvac-Riko</td><td>ZEM-2</td><td></td></tr><tr><td>Laser Flash Thermal Diffusivity Measurement System</td><td>Netzsch</td><td>LFA-457 Microflash</td><td></td></tr><tr><td>Differential Scanning Calorimetry (DSC) System</td><td>Netzsch</td><td>404C Pegasus</td><td></td></tr><tr><td>Physical Property Measurement system (PPMS)</td><td>Quantum Design</td><td></td><td></td></tr><tr><td>Field Emission Scanning Electron Microscope (FE-SEM)</td><td>Hitachi</td><td>SU-6600</td><td></td></tr><tr><td>Energyy-dispersive X-ray Spectroscopy (EDS)</td><td>Oxford Instruments</td><td></td><td></td></tr><tr><td>X-ray Diffractometer</td><td>Rigaku</td><td>Ultima IV</td><td></td></tr><tr><td>Bench-top Sputter Coater</td><td>Denton Vacuum</td><td>Desk II</td><td></td></tr><tr><td>Diamond&amp;nbsp; Wheel Saw</td><td>South Bay Technology</td><td></td><td></td></tr></tbody></table>

synthesis of non-uniformly pr-doped srtio3 ceramics and their thermoelectric properties

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

Padrões de difracção de raios-X foram recolhidos como para os pós preparados e as correspondentes massa cerâmica em função do conteúdo-Pr (Figura 1), a fim de estudar o efeito do Pr-dopagem na SrTiO 3 estrutura, a solubilidade do Pr em SrTiO 3 e a formação da fase secundária (s). Os padrões de confirmar a formação de SrTiO 3 fase em todos os pós preparados como onde as reflexões podem ser indexados para uma rede cúbica com grupo espacial (Figura ...

Watch this Scientific Journal Video about Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties at JoVE.com

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

Síntese de não-uniforme Pr-dopado SrTiO<sub&gt; 3</sub&gt; Cerâmica e suas propriedades termoelétricas

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma ...

synthesis-non-uniformly-pr-doped-srtio3-ceramics-their-thermoelectric

Research

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Chemistry

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

9.8K visualizações.  Clemson University. A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

Vídeo: Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

Fabrication of Spatially Confined Complex Oxides

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from the inherent strong electron correlations that reside within them. These materials can also possess electronic phase separation in which regions of vastly different resistive and magnetic behavior can coexist within a single crystal alloy material. By reducing the scale of these materials to length scales at and below the inherent size of the electronic domains, novel behaviors can be exposed. Because of this and the fact that spin-charge-lattice-orbital order parameters each involve correlation lengths, spatially reducing these materials for transport measurements is a critical step in understanding the fundamental physics that drives complex behaviors. These materials also offer great potential to become the next generation of electronic devices 1-3. Thus, the fabrication of low dimensional nano- or micro-structures is extremely important to achieve new functionality. This involves multiple controllable processes from high quality thin film growth to accurate electronic property characterization. Here, we present fabrication protocols of high quality microstructures for complex oxide manganite devices. Detailed descriptions and required equipment of thin film growth, photo-lithography, and wire-bonding are presented.

We describe the use of pulsed laser deposition (PLD), photolithography and wire-bonding techniques to create micrometer scale complex oxides devices. The PLD is utilized to grow epitaxial thin films. Photolithography and wire-bonding techniques are introduced to create practical devices for measurement purposes.

Fabricação de óxidos complexos espacialmente confinados

Complex materials such as high Tc superconductors, multiferroics, and colossal magnetoresistors have electronic and magnetic properties that arise from ...

Engenharia

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

Templates atomicamente definidos para crescimento epitaxial do Complexo Óxido Filmes Finos

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

Química

Synthesis and Reaction Chemistry of Nanosize Monosodium Titanate

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the material with Au(III) ions. The synthesis method was derived from a sol-gel process used to produce micron-sized monosodium titanate (MST), with several key modifications, including altering reagent concentrations, omitting a particle seed step, and introducing a non-ionic surfactant to facilitate control of particle formation and growth. The resultant nMST material exhibits spherical-shaped particle morphology with a monodisperse distribution of particle diameters in the range from 100 to 150&#160;nm. The nMST material was found to have a Brunauer-Emmett-Teller (BET) surface area of 285 m2g-1, which is more than an order of magnitude higher than the micron-sized MST. The isoelectric point of the nMST measured 3.34 pH units, which is a pH unit lower than that measured for the micron-size MST. The nMST material was found to serve as an effective ion exchanger under weakly acidic conditions for the preparation of an Au(III)-exchange nanotitanate. In addition, the formation of the corresponding peroxotitanate was demonstrated by reaction of the nMST with hydrogen peroxide.

The surfactant mediated sol-gel synthesis of nanosized monosodium titanate is described, along with preparation of the corresponding peroxide modified material. An ion-exchange reaction with Au(III) is also presented.

Síntese e Reacção Química de nanosize monossódico Titanate

This paper describes the synthesis and peroxide-modification of nanosize monosodium titanate (nMST), along with an ion-exchange reaction to load the ...

Epitaxial Growth of Perovskite Strontium Titanate on Germanium via Atomic Layer Deposition

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and conformality by taking advantage of self-limiting reactions between vapor-phase precursors and the growing film. Perovskite oxides present potential for next-generation electronic materials, but to-date have mostly been deposited by physical methods. This work outlines a method for depositing SrTiO3 (STO) on germanium using ALD. Germanium has higher carrier mobilities than silicon and therefore offers an alternative semiconductor material with faster device operation. This method takes advantage of the instability of germanium's native oxide by using thermal deoxidation to clean and reconstruct the Ge (001) surface to the 2&#215;1 structure. 2-nm thick, amorphous STO is then deposited by ALD. The STO film is annealed under ultra-high vacuum and crystallizes on the reconstructed Ge surface. Reflection high-energy electron diffraction (RHEED) is used during this annealing step to monitor the STO crystallization. The thin, crystalline layer of STO acts as a template for subsequent growth of STO that is crystalline as-grown, as confirmed by RHEED. In situ X-ray photoelectron spectroscopy is used to verify film stoichiometry before and after the annealing step, as well as after subsequent STO growth. This procedure provides framework for additional perovskite oxides to be deposited on semiconductors via chemical methods in addition to the integration of more sophisticated heterostructures already achievable by physical methods.

This work details the procedures for the growth and characterization of crystalline SrTiO3 directly on germanium substrates by atomic layer deposition. The procedure illustrates the ability of an all-chemical growth method to integrate oxides monolithically onto semiconductors for metal-oxide semiconductor devices.

Crescimento epitaxial de Perovskita titanato de estrôncio em Germânio via deposição de camadas Atomic

Atomic layer deposition (ALD) is a commercially utilized deposition method for electronic materials. ALD growth of thin films offers thickness control and ...

Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with one twist grain boundary. This apparatus utilizes high uniaxial pressure and a pulsed direct current for rapid consolidation of material. Diffusion bonding of strontium titanate bicrystals without fracture, in a spark plasma sintering apparatus, is possible at high pressures due to the unusual temperature dependent plasticity behavior of strontium titanate. We demonstrate a method for the successful formation of bicrystals at accelerated time scales and lower temperatures in a spark plasma sintering apparatus compared to bicrystals formed by conventional diffusion bonding parameters. Bond quality was verified by scanning electron microscopy. A clean and atomically abrupt interface containing no secondary phases was observed using transmission electron microscopy techniques. Local changes in bonding across the boundary was characterized by simultaneous scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy.

A viable technique for the formation of strontium titanate bicrystals at high pressure and fast heating rate via the spark plasma sintering apparatus is developed.

Faísca Plasma Sintering aparelho utilizado para a Formação de titanato de estrôncio Bicrystals

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with ...

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide electronics community. One of its hallmark features is the existence of a critical LAO thickness of 4 unit-cells (uc) for interfacial conductivity to emerge. Although electrostatic mechanisms have been proposed in the past to describe the existence of this critical thickness, the importance of chemical defects has been recently accentuated. Here, we describe the growth of metal/LAO/STO heterostructures in an ultra-high vacuum (UHV) cluster system combining pulsed laser deposition (to grow the LAO), magnetron sputtering (to grow the metal) and X-ray photoelectron spectroscopy (XPS). We study step by step the formation and evolution of the q2DES and the chemical interactions that occur between the metal and the LAO/STO. Additionally, magnetotransport experiments elucidate on the transport and electronic properties of the q2DES. This systematic work not only demonstrates a way to study the electrostatic and chemical interplay between the q2DES and its environment, but also unlocks the possibility to couple multifunctional capping layers with the rich physics observed in two-dimensional electron systems, allowing the fabrication of new types of devices.

Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures

We fabricate metal/LaAlO3/SrTiO3 heterostructures using a combination of pulsed laser deposition and in situ magnetron sputtering. Through magnetotransport and in situ X-ray photoelectron spectroscopy experiments, we investigate the interplay between electrostatic and chemical phenomena of the quasi two-dimensional electron gas formed in this system.

Crescimento e eletrostático química/Propriedades de Metal/LaAlO3/SrTiO3 estende

The quasi 2D electron system (q2DES) that forms at the interface between LaAlO3 (LAO) and SrTiO3 (STO) has attracted much attention from the oxide ...

Chemical Synthesis of Porous Barium Titanate Thin Film and Thermal Stabilization of Ferroelectric Phase by Porosity-Induced Strain

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its well-balanced ferroelectricity, piezoelectricity, and dielectric constant. In addition, BT does not contain any toxic elements. Therefore, it is considered to be an eco-friendly material, which has attracted considerable interest as a replacement for lead zirconate titanate (PZT). However, bulk BT loses its ferroelectricity at approximately 130 &#176;C, thus, it cannot be used at high temperatures. Because of the growing demand for high-temperature ferroelectric materials, it is important to enhance the thermal stability of ferroelectricity in BT. In previous studies, strain originating from the lattice mismatch at hetero-interfaces has been used. However, the sample preparation in this approach requires complicated and expensive physical processes, which are undesirable for practical applications.
In this study, we propose a chemical synthesis of a porous material as an alternative means of introducing strain. We synthesized a porous BT thin film using a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles were used as an organic template. Through a series of studies, we clarified that the introduction of pores had a similar effect on distorting the BT crystal lattice, to that of a hetero-interface, leading to the enhancement and stabilization of ferroelectricity. Owing to its simplicity and cost effectiveness, this fabrication process has considerable advantages over conventional methods.

Here, we present a protocol for the synthesis of porous barium titanate (BaTiO3) thin film by a surfactant-assisted sol-gel method, in which self-assembled amphipathic surfactant micelles are used as an organic template.

Síntese química de película fina de titanato de bário porosa e estabilização térmica da fase ferroelétrica pela tensão induzida pela porosidade

Barium titanate (BaTiO3, hereafter BT) is an established ferroelectric material first discovered in the 1940s and still widely used because of its ...

Bulk and Thin Film Synthesis of Compositionally Variant Entropy-stabilized Oxides

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (Cu variant) entropy-stabilized oxides. Phase pure and chemically homogeneous (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (x = 0.20, 0.27, 0.33) and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O (x = 0.11, 0.27) ceramic pellets are synthesized and used in the deposition of ultra-high quality, phase pure, single crystalline thin films of the target stoichiometry. A detailed methodology for the deposition of smooth, chemically homogeneous, entropy-stabilized oxide thin films by pulsed laser deposition on (001)-oriented MgO substrates is described. The phase and crystallinity of bulk and thin film materials are confirmed using X-ray diffraction. Composition and chemical homogeneity are confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. The surface topography of thin films is measured with scanning probe microscopy. The synthesis of high quality, single crystalline, entropy-stabilized oxide thin films enables the study of interface, size, strain, and disorder effects on the properties in this new class of highly disordered oxide materials.

The synthesis of high quality bulk and thin film (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O and (Mg0.25(1-x)Co0.25(1-x)Ni0.25(1-x)CuxZn0.25(1-x))O entropy-stabilized oxides is presented.

Granel e síntese de película fina de óxidos de entropia-estabilizado em termos de composição variantes

Here, we present a procedure for the synthesis of bulk and thin film multicomponent (Mg0.25(1-x)CoxNi0.25(1-x)Cu0.25(1-x)Zn0.25(1-x))O (Co variant) and ...

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing

Electrical, optical, and magnetic properties of oxide materials can often be controlled by varying the oxygen content. Here we outline two approaches for varying the oxygen content and provide concrete examples for tuning the electrical properties of SrTiO3-based heterostructures. In the first approach, the oxygen content is controlled by varying the deposition parameters during a pulsed laser deposition. In the second approach, the oxygen content is tuned by subjecting the samples to annealing in oxygen at elevated temperatures after the film growth. The approaches can be used for a wide range of oxides and nonoxide materials where the properties are sensitive to a change in the oxidation state.
The approaches differ significantly from electrostatic gating, which is often used to change the electronic properties of confined electronic systems such as those observed in SrTiO3-based heterostructures. By controlling the oxygen vacancy concentration, we are able to control the carrier density over many orders of magnitude, even in nonconfined electronic systems. Moreover, properties can be controlled, which are not sensitive to the density of itinerant electrons.

Oxide materials show many exotic properties that can be controlled by tuning the oxygen content. Here, we demonstrate the tuning of oxygen content in oxides by varying the pulsed laser deposition parameters and by performing postannealing. As an example, electronic properties of SrTiO3-based heterostructures are tuned by growth modifications and annealing.

Ajuste das propriedades do óxido pelo controle de vacância de oxigênio durante o crescimento e recozimento

Electrical, optical, and magnetic properties of oxide materials can often be controlled by varying the oxygen content. Here we outline two approaches for ...

Deposição de filmes finos Bi2Te3 e Sb2Te3 em substratos de vidro via pulverização catódica por RF

Fabrication of Bi2Te3 and Sb2Te3 Thermoelectric Thin Films using Radio Frequency Magnetron Sputtering Technique

Through various studies on thermoelectric (TE) materials, thin film configuration gives superior advantages over conventional bulk TEs, including adaptability to curved and flexible substrates. Several different thin film deposition methods have been explored, yet magnetron sputtering is still favorable due to its high deposition efficiency and scalability. Therefore, this study aims to fabricate a bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thin film via the radio frequency (RF) magnetron sputtering method. The thin films were deposited on soda lime glass substrates at ambient temperature. The substrates were first washed using water and soap, ultrasonically cleaned with methanol, acetone, ethanol, and deionized water for 10 min, dried with nitrogen gas and hot plate, and finally treated under UV ozone for 10 min to remove residues before the coating process. A sputter target of Bi2Te3 and Sb2Te3 with Argon gas was used, and pre-sputtering was done to clean the target&#39;s surface. Then, a few clean substrates were loaded into the sputtering chamber, and the chamber was vacuumed until the pressure reached 2 x 10-5 Torr. The thin films were deposited for 60 min with Argon flow of 4 sccm and RF power at 75 W and 30 W for Bi2Te3 and Sb2Te3, respectively. This method resulted in highly uniform n-type Bi2Te3 and p-type Sb2Te3 thin films.

Autor em destaque: Avanços em filmes finos termoelétricos de alto desempenho por meio de pulverização catódica de magnetron de radiofrequência

The manuscript describes a protocol for radio frequency magnetron sputtering of Bi2Te3 and Sb2Te3 thermoelectric thin films on glass substrates, which represents a reliable deposition method that provides a wide range of applications with the potential for further development.

Fabricação de Filmes Finos Termoelétricos Bi2Te3 e Sb2Te3 utilizando a Técnica de Sputtering por Magnetron de Radiofrequência

Síntese de não-uniforme Pr-dopado SrTiO

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