Chiang Mai Journal of Science

The hexagonal polymorph of BaTiO₃ (P6₃/mmc) was stabilised at room temperature by partial replacement of Ti with Mn, where Ba(Ti_1-xMn_x)O₃ (0.05d” x d”0.3) was prepared from mixed oxide route at 1,250^ºC. The phase-purity and lattice parameters of calcined powders and sintered pellets were examined by X–ray diffraction (XRD) using the index scheme for undoped 6h- BaTiO₃ (reported in the ICDD file number 82-1175 as space group P6₃/mmc with lattice parameters of a = 5.72380(70) Å, c = 13.96490(70) Å, V = 396.2 ų). The average grain size of samples was measured and found to be 5-50 µm in width and 8-120 µm in length for Ba(Ti_0.95Mn_0.05)O₃ , 3-5 µm for Ba(Ti_0.90Mn_0.10)O₃, 4-6 µm for Ba(Ti_0.80Mn_0.20)O₃ and 3-6  µm for Ba(Ti_0.70Mn_0.30)O₃ The impedance measurements were conducted at . 300–500°C, in the frequency range from 5 Hz to 13 MHz, to separate grain and grain boundary contributions. The grain and grain boundaries relaxation frequencies were shifted to higher frequency with increasing temperature. Bulk resistance of Mn-doped BaTiO₃ ceramics was 2.32×10⁵ Ωcm for Ba(Ti_0.95Mn_0.05)O₃, 1.04×10⁶Ωcm for Ba(Ti_0.90Mn_0.10)O₃, 2.46×10⁵Ωcm for Ba(Ti_0.80Mn_0.20)O₃ and 10709 Ωcm for Ba(Ti_0.70Mn_0.30)O₃ Single grain boundary resistance .indicated that grain boundary resistance increased with acceptor doping. Activation energies were calculated to be in the range of  0.651-0.851 eV.