Netsu Sokutei, 48 (1), p. 7, (2021)

特集 - 物性研究における熱測定・熱分析 -


Low-Temperature β-β’ Phase Transition Phenomenon on La2Mo2O9-based Oxide Ion Conductors

La2Mo2O9-based system is one of the widely investigated oxide ion conductors for its excellent ionic conductivity at intermediate temperatures. The detailed phase relationships and transition phenomena also attract interests in combination with oxide ion conduction. In recent years, we found that low-temperature stable phase (β’-phase) with the quite similar structure with β-phase appears by annealing the supercooled β below 460 oC for the sample x ~ 0.06 of La2-xBixMo2O9, and the transformation process from β into β’ can be expressed based on Avrami’s equation. In addition, Ba- or Pb-substituted systems also exhibit the low-temperature β’ phase through the annealing of supercooled β-phase. The electron diffraction and thermal hysteresis of conductivity suggested that subtle ordering of oxide ion is related to the formation of β’-phase. In this article, we show our recent research on the low-temperature phase transition phenomena on La2Mo2O9-based oxide ion conductors.