Structure Sequence in the CaTiO 3 –LaAlO 3 Microwave Ceramics—Revised

The composition‐induced crystal structure transformations in the (1− x )CaTiO 3 – x LaAlO 3 microwave ceramics were studied by X‐ray powder diffraction. Increasing LaAlO 3 content results in two‐phase transitions: Pnma → Imma (0.4< x <0.5) and Imma → R 3 c (0.5< x <0.6), which are related to changes of the octahedral tilting: a − b + a − → a − b 0 a − and a − b 0 a − → a − a − a − , respectively. The compositional variation of the parameters of the primitive perovskite unit cell is consistent with a continuous character of the Pnma → Imma phase transition. In the case of the Imma → R 3 c crossover, a discontinuity in the variation is observed.