Effect of spark plasma sintering temperature on the phase equilibria and dielectric properties of BaTi2O5 ceramics

The effect of sintering temperature (ranging from 1055 to 1200 °C) on the phase ingredient and dielectric property of the nominal BaTi2O5 ceramics (starting with the Ba/Ti of 1:2) fabricated by a spark plasma sintering method were systematically studied. At the first stage, BaTi2O5 component was enhanced in the sintering temperature range of 1055–1120 °C; it turned out to be the dominant phase. For these BaTi2O5 phase dominated ceramics, the Curie temperature T c rised on increasing the sintering temperature and saturated around 440 °C with the maximum dielectric constant of 500. Further increasing the sintering temperature, the decomposition of the obtained BaTi2O5 into BaTiO3 extensively happened; the ceramics turned to be the BaTi2O5 and BaTiO3 coexisting state. These ceramics can be characterized by two dielectric anomalies. One at ~420 °C stood for the phase transition of BaTi2O5 while the other at ~150 °C stood for the transition of BaTiO3, which is exceptionally high as the normal BaTiO3 ceramics. Further increasing the sintering temperature (until 1200 °C) would dramatically enhance the BaTiO3 phase; the ceramics showed T c at 130 °C with the maximum dielectric constant of 1800.