Probing the structural, optical absorption, dielectric and impedance properties of Sr-modified BaMnO3 ceramics

This work probes the structural, optical and temperature-dependent dielectric properties of BaMnO₃ and Ba_0.9Sr_0.1MnO₃multiferroic ceramics prepared by conventional solid state reaction technique. XRD analysis indicates rhombohedral perovskite structure of BaMnO₃. When 10 wt.% Sr is added in the BaMnO₃ matrix against Ba, the rhombohedral structure transforms into hexagonal perovskite structure. The average crystallite size of BaMnO₃ and Ba_0.9Sr_0.1MnO₃were found to be ~ 92 nm and ~ 63 nm, respectively. The lattice parameter and the unit cell volume also decrease with the addition of Sr in pure BaMnO₃. Through EDX analysis, the presence of all the constituents in the final samples are verified. The optical band gap of BaMnO₃ decreases from 2.33 eV to 1.75 eV, primarily attributed to SrMnO₃ phase and grain boundary effects. A much higher value of dielectric constant i.e. ~ 19,800 at 200 °C with respect to 10 Hz frequency has been achieved with 10 wt.% strontium doping in BaMnO₃, which may boost the efficiency of electronic devices made up of dielectric materials. The impedance analysis confirms the negative temperature coefficient of resistance (NTCR) behaviour of the sample and semicircular arc Nyquist plot supports the semiconducting nature with non-Debye type of relaxation mechanism in both the samples.