Electrical properties of 6H-BaTi0.95M0.0O3-δ ceramics where M = Mn, Fe, Co and Ni

Hexagonal BaTiO3 materials have been stabilised at room temperature according to the formula BaTi0.95M0.05 O3-delta where M = Mn, Fe, Co and Ni. Dense ceramics (>96% of the theoretical X-ray density) were sintered at 1450degreesC in flowing O-2 gas from calcined powders prepared by the mixed oxide route at 1300degreesC. All samples were single-phase and the bulk conductivity, sigma(b), measured by Impedance Spectroscopy and Q.f measured by microwave dielectric resonance methods showed a strong dependence on the type of dopant. sigma(b) at 300degreesC was 10(-7), 10(-5.5), 10(-5.5) and 10(-4) Scm(-1) for M = Mn, Fe, Ni and Co, respectively and Q.f at similar to 5 GHz was 7790, 6670, 2442 and 1291 GHz, for M = Mn, Fe, Ni and Co, respectively. The correlation between sigma(b) and Qf is attributed to the presence of oxygen vacancies and/or mixed valency of the dopant ions.