Synthesis, characterization, thermal, and electrical properties of new diammonium hybrid perovskite [NH3-(CH2)7-NH3]CaCl2Br2

The layered organic-inorganic hybrid of [NH3-(CH2)7-NH3]CaCl2Br2 has been synthesized from ethanolic solution by gradual cooling to room temperature. The reaction molar ratio is (1:1) organic/inorganic. Formation of the hybrid was confirmed by microchemical analysis, FTIR, and XRD. Thermal analysis DSC shows four transitions associated with solid-solid phase change, one major transition at T3 = 330 ± 2 K, entropy ΔS3 = 13.65 J/mol-K associated with order-disorder phase transition, and three minor transitions at T1 = 420 K, ΔS1 = 0.19 J/mol-K, T2 = 338 K, ΔS2 = 0.85 J/mol-K, and T4 = 319 K, ΔS4 = 1.58 J/mol-K. Dielectric permittivity and AC conductivity as a function of temperature (295 < T(K) < 435) at selected frequencies (0.06 < f (kHz) < 20) are presented. Permittivity results indicate the presence of phase transition at T = 332 K. AC conductivity is thermally activated in different phases. The activation energy values range from 0.02 to 1.1 eV depending upon the temperature range and the applied frequencies.