Phase formation mechanism and characteristics of strontium barium niobate ceramics

Ceramic powders of (1 − x)BaNb2O6-xSrNb2O6 (0 ≤ x ≤ 1) composition were prepared by solid-state reaction. Thermal analysis data revealed that SrNb2O6 was formed at a lower temperature, compared with BaNb2O6. Ba1−xSrxNb2O6 mixtures show an intermediate thermal behaviour. For the samples thermally treated at 1000 °C/3 h, X-ray diffraction data pointed out single phase compositions for x = 0.4-0.6, which means that SrNb2O6 completely dissolves into BaNb2O6 lattice in this composition range The temperature increase at 1150 °C leads to partial decomposition and supplementary demixing phenomena for all the mixtures analyzed. At 1300 °C, solid-state reactions progress and a structural rearrangement occurs, so that the same phase composition identified at 1000 °C was found again. A slight increase of the isomorphy limit of SrNb2O6 into BaNb2O6 lattice was also noticed. Single-phase compositions were identified for the samples with x = 0.3-0.6.