Low intrinsic thermal conductivity of Spark Plasma Sintered dense KNbO3 and NaNbO3 perovskite ceramics

• Published in: Thermochimica acta 2021-01, Vol.695, p.178807, Article 178807
• Main Authors: Delorme, F., Chen, C., Schoenstein, F., Jaber, N., Jean, F., Bah, M., Simon, Q., Chartier, T., Laffez, P., Monot-Laffez, I., Giovannelli, F.
• Format: Article
• Language: English
• Subjects: Ceramics; Chemical Sciences; Condensed Matter; Cristallography; Engineering Sciences; Inorganic chemistry; Materials; Materials Science; Perovskite; Physics; Spark plasma sintering; Strongly Correlated Electrons; Superconductivity; Thermal conductivity
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2020.178807

•NaNbO3 ceramic thermal conductivity is 2.6 W m−1 K−1 at 1000 K.•KNbO3 ceramic thermal conductivity is 1.2 W m−1 K−1 at 1000 K.•NaNbO3 and KNbO3 ceramics exhibit an alkali deficiency.•The origin of the low thermal conductivities is related to the alkali deficiency. The origin of low thermal conductivity in niobium-containing perovskites was investigated. Therefore, dense NaNbO3 and KNbO3 ceramics were sintered by spark plasma sintering. The grain size was in the 1–10 μm range. NaNbO3 ceramic has shown a stable thermal conductivity circa 2.6 W m−1 K−1 from 373 to 1000 K and KNbO3, values from 2.5 to a plateau at 1.2 W m−1 K−1 since 673 K. This value is the lowest thermal conductivity reported for an oxide presenting a perovskite structure. The origin of such low thermal conductivities is indicated to be related with cation deficiency on the A-site of the niobium-containing perovskites.