Thermal expansion in the Burns-phase of barium titanate stannate

The thermal expansion ST has been measured in the system BaTi1−xSnxO3, 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 ST(T) has been observed at elevated temperatures T>400 K. This is related to thermally generated impurities and, below the Burns-temperature Td 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.