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

Abstract

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.