Impedance spectroscopy studies of SrMnO3, BaMnO3and Ba0.5Sr0.5MnO3ceramics

The impedance spectrum of hexagonal SrMnO3, rhombohedral BaMnO3 and orthorhombic Ba0.5Sr0.5MnO3 ceramics, synthesized by conventional high-temperature method, was studied in a wide temperature and frequency range. The complex impedance plots of Z″ versus Z′ pointed to two contributions originating from grains and grain boundaries. The parameters of electric equivalent circuit were calculated. The semicircles related to the grain boundary are located at the lower frequency side due to higher resistivity and capacity of the grain boundaries. The Ba0.5Sr0.5MnO3 ceramics is characterized by the lowest activation energy related to the grains. The conductivities σac of all the investigated samples show plateaus being a characteristic of the dc conductivity. The conductivity of Ba0.5Sr0.5MnO3 takes the values between those of BaMnO3 and SrMnO3.