Effect of doping B₂O₃ on cell parameters and transition temperature of Ba_1-xSr_xTiO₃ ceramics

The stability of perovskite structure, cell parameters and phase transition temperature of sintered B₂O₃-doped Ba_1-xSr_xTiO₃ (x=0-1) ceramics were investigated. The results show that, with dopant amount increasing, the perovskite structure is maintained but the cell parameters are changed slightly. The c and a change irregularly, while c/a and cell volume (a²c) monotonously decreases and increases respectively. The trasition temperature of doped Ba_1-xSr_xTiO₃ will rise a little, compared with that of undoped ones. With sintering temperature rising, transition temperature decreases since cell volume contracts due to solutionizing of Ba and Sr (with the same dopant content). But with dopant amount increasing, the transition temperature changes hardly (with the same sintering temperature). It means that B₂O₃ does affect the cell parameters of Ba_1-xSr_xTiO₃, although the ionic radius of B³⁺ is very small; B³⁺ entered and stayed in the cell in interstitial mode, but its solid solubility is very limited.