Figure depicts the phase development above 1050 °C. The lattice parameters of BaZrO3 are converging with those of the BCZT matrix between 1050 °C and 1200 °C, while the overall amount of this phase is diminishing. This dissolution occurs via interdiffusion between BaZrO3 and the BCZT matrix, and the process is thermally activated only above approximately 1100 °C. A similar formation of a solid solution between BaZrO3 and BaTiO3 was observed by Bera et al. . It is assumed that the matrix ions mostly diffuse into BaZrO3, which represents the host lattice. The molar fractions of the different phases are displayed in Figure (for the analysis of the individual phase compositions see Table ). While BaZrO3 disappears at 1250 °C, the amount of segregated CaTiO3 increases up to 1150 °C, followed by a steady decrease and a full dissolution at 1400 °C. The unit cell volumes of the BCZT matrix, CaTiO3, and BaZrO3 over the whole temperature range were calculated from the refined lattice parameters (Figure ). The volume of CaTiO3 expands almost linearly with temperature, with a slope approximately matching the expected thermal expansion ,