Thermal expansion in the Burns-phase of barium titanate stannate

The thermal expansion S_T has been measured in the system BaTi_1−xSn_xO₃, both for the pure compositions x=0 (BT) and x=1 (BS), and for solid solutions 0.025≤x≤0.2 (BTS). For all ceramics examined, a non-linear temperature dependence S_T(T) has been observed at elevated temperatures This is related to thermally generated impurities and, below the Burns-temperature T_d of BT and BTS, to the non-linear strain contribution of polar nanoregions. With increasing Sn-content x, a steep increase of the Burns-temperature is found in BTS for compositions x≥0.025.