Effect of Mn doping on dielectric response and optical band gap of LaGaO 3

Abstract

In order to realize the effect of Mn doping on dielectric behavior and optical band gap (E g ) of Lanthanum Gallate; pure and Mn doped LaGaO 3 samples were prepared. The phase purity of these samples was confirmed by x-ray diffraction experiments. It was found that all samples possess orthorhombic structure. Room temperature (RT) dielectric response and E g of LaGa 1−x Mn x O 3 (LGMO) with, x = 0.0 to 0.9, has been recorded using impedance analyzer (LCR meter) and diffuse reflectance spectroscopy respectively. It has been observed that at RT, pure LaGaO 3 exhibits moderate dielectric constant (ε′ ≈ 25) with very low dielectric loss (tan δ). Interestingly, the value of RT ε′ significantly increases with Mn doping whereas tan δ remains relatively low upto x = 0.4 and increases abruptly x > 0.4. The observed increase in ε′ and tan δ with Mn doping has been understood in terms of structural coherency and systematic decrease in E g . A shift in ε′-anomaly (tan δ-peak) with increasing Mn percentage and low frequency large ε′ were also observed in Mn doped LGO. Both of these effects have been understood in terms of coexisting Mn 3+ and Mn 4+ ions. The LGMO samples (x ≤ 0.4) showing high value of ε′ and very low tan δ can be suitable candidates for capacitive applications. © 2017, © 2017 Informa UK Limited, trading as Taylor & Francis Group.