Effect of isovalent substitution of La3+ in Ca-doped LaNbO4 on the thermal and electrical properties

Abstract The effect of the equimolar substitution of lanthanum in Ca-doped LaNbO 4 on the functionality of (La 0.5 Ln 0.5 ) 0.99 Сa 0.01 NbO 4–δ (where Ln = La, Nd and Sm) is investigated in the present work. Highly dense, single-phase and of microstructurally quality ceramic samples are synthesized, using a solid state reaction method. The relation between Ln 3+ ionic radii with thermal and electrical properties is successfully revealed. It is found that the partial substitution with other lanthanides can be considered as a promising tool to suppress thermal expansion differences between low- and high-temperature modifications of lanthanum niobates; however, at the same time, the ionic conductivity decreases, which requires searching the trade-off for the optimal composition identification.