Phase transition and electric properties of long chain Cd(II) layered perovskites

Abstract

The new layered perovskite [(CH₂)₁₂(NH₃)₂]CdCl₄ material exhibits a second order phase transition at T _1p = 376.8 K (ΔS ₁ ≃ 12.5 J K⁻¹ mol⁻¹) of the order–disorder type. The dielectric permittivity has been studied in the temperature range 300–400 K and frequency range 0.1–100 kHz, on heating and cooling. The ac conductivity is thermally activated with different activation energies in the range of ionic conduction. The variation of ac conductivity with frequency follows the power law:

Proton hopping and localised reorientational motion, ionic hopping of chlorine vacancies and large polarons are possible conduction mechanisms in the different temperature ranges. Comparison with other isomorphous transition metal perovskites is discussed.

Keywords:

• Phase transition
• Transport properties
• Conduction in layered perovskites
• Permittivity studies

Acknowledgment

The authors would like to acknowledge the support of the Egyptian Ministry of International Cooperation.