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Synthesis,sintering,and thermoelectric properties of the solid solution La_(1–x)Sr_(x)CoO_(3±δ)(0≤x≤1)

Journal of Advanced Ceramics 2018年第2期7卷 160-168页

作者： M.A.BOUSNINA R.DUJARDIN L.PERRIERE F.gIOVANNELLI g.guegan F.DELORME UniversitéFrancois Rabelais de Tours CNRSINSA CVLGREMAN UMR7347IUT de Blois ICMPE ST Microelectronics

In this work, we synthesized cubic perovskite ceramics of the whole La_(1–x)Sr_xCoO_3(0 ≤ x ≤ 1) solid solution for the first time. Synthesis was carried out by solid state reaction and conventional sintering to reach dense ceramics. For x > 0.8, it was necessary to substitute 3% cobalt by silicon to stabilize the cubic perovskite structure. Electrical conductivity increased with Sr content to reach 3×10~5 S·m^(–1) at 330 K for x = 0.3. However, the optimum electrical properties have been found for x = 0.05 at 330 K with PF_(max) = 3.11×10^(–4)W·m^(–1)·K^(–2). Indeed, the Seebeck coefficient was decreasing when x increased to reach values close to 0 for x ≥ 0.3. Thermal conductivity was low at low temperature(≈ 2.5 W×m^(–1)·K^(–1)) and increased up to 6.5 W·m^(–1)·K^(–1) when temperature increased. As the highest power factor was reached at low temperature as well as the lowest thermal conductivity, La_(1–x)Sr_xCoO_3 compounds with low x values appeared as very promising thermoelectric materials around room temperature, on the contrary to layered cobalt oxides. For high x values, Seebeck coefficient values close to zero made these materials unsuitable for thermoelectric applications.

关键词： perovskite cobalt oxide solid solution electrical conductivity thermoelectric

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Ba substitution for enhancement of the thermoelectric properties of LaCoO_(3) ceramics(0≤x≤0.75)

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Journal of Advanced Ceramics 2019年第4期8卷 519-526页

作者： Mohamed Ali BOUSNINA Fabien gIOVANNELLI Loic PERRIERE guillaume guegan Fabian DELORME Université Francois Rabelais de Tours CNRSINSA CVLGREMAN UMR7347IUT de Blois15 rue de la chocolaterieCS2903F-41029 Blois CedexFrance UniversitéParis 13 Sorbonne Paris CiteLaboratoire des Sciences des Procédés et des MatériauxCNRSUPR 340799 avenue J.B.ClémentF-93430 VilletaneuseFrance Institut de Chimie et des Matériaux Paris-Est UMR 7182 CNRS-UPEC2-8 Rue Henri Dunant94320 ThiaisFrance ST Microelectronics 16 Rue Pierre et Marie CurieTours 37100France

In the present work, dense perovskite ceramics were successfully prepared from a series of La1-xBaxCoO3 solid solutions in the range of substitution 0 ≤ x ≤ 0.75 using solid state reaction and conventional sintering. Structural properties of La1-xBaxCoO3 were systematically investigated and thermoelectric properties were measured in the temperature range of 330–1000 K. The results show that the thermoelectric properties of Ba-substituted LaCoO3 depend on x. Indeed, at 330 K, electrical conductivity presents an optimum value for x = 0.25 with a value of σmax ≈ 2.2×105 S·m–1 whereas the Seebeck coefficient decreases when x and/or the temperature increases. The Ba-substituted LaCoO3 samples exhibit p-type semiconducting behaviour. The best power factor value found is 3.4×10–4 W·m–1·K–2 at 330 K for x = 0.075, which is 10% higher than the optimum value measured in La1–xSrxCoO3 for x = 0.05. The thermal diffusivity and thermal conductivity increase with increasing temperature and Ba concentration. La1-xBaxCoO3 shows a maximum figure of merit(ZT = 0.048) for x = 0.05 at 330 K, 25% higher than the best value in La1–xSrxCoO3 compounds.

关键词： perovskite Ba-substituted LaCoO_(3) oxide thermoelectric p-type semiconductor

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