Abstract
We have studied the structural and dielectric properties of La0.8Te0.2MnO3 pervoskite compound, has a rhombohedral structure with space group R-3c, at room temperature. Infrared spectrum shows two active bands located at 611 and 410cm−1, which can be ascribed to the internal stretching and bending phonon modes. The additional bands observed at 925, 969 and 1383cm−1 are attributed to the multiphonon scattering. The dielectric constant ε′ shows a step like relaxation behaviour and has been discussed with in the frame work of the Kramers–Kronig transformation model. The ac conductivity follows a universal dielectric response (UDR), and the results were discussed and fitted with the Jump relaxation model (JRM). The occurrence of giant or colossal dielectric constant is most likely due to electrode polarization or interface polarization effect. The depletion layers are arising due to the formation of Schottky barriers at the metallic contacts of semiconducting samples, which may be formed by grain boundaries, can give rise to Maxwell–Wagner type relaxation and apparently very high dielectric constants.
► La0.8Te0.2MnO3 has a rhombohedral crystal structure with space group R3¯c. ► The system shows CDC behaviour, attributed to the contact effects. ► AC conductivity shows a universal dielectric response (UDR) behaviour. ► The results of ε′(ν) and σ′ac(υ) are fitted with KKT and JR models respectively. ► The variation of s vs. T follows the overlapping large polaron tunnelling (OLPT) model.