Electrical Properties of 6H-BaTi0.95M0.05O3?? 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−δ where M = Mn, Fe, Co and Ni. Dense ceramics (> 96% of the theoretical X-ray density) were sintered at 1450∘C in flowing O2 gas from calcined powders prepared by the mixed oxide route at 1300∘C. All samples were single-phase and the bulk conductivity, σb, measured by Impedance Spectroscopy and Q.f measured by microwave dielectric resonance methods showed a strong dependence on the type of dopant. σb at 300∘C 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 ∼ 5 GHz was 7790, 6670, 2442 and 1291 GHz, for M = Mn, Fe, Ni and Co, respectively. The correlation between σb and Q.f is attributed to the presence of oxygen vacancies and/or mixed valency of the dopant ions.