Electrical and thermal investigations of energetic material (n-C16H33NH3)2CdCl4

Abstract

The thermal energy storage material, namely hexadecyl ammonium tetrachloro cadmate (n-C16H33NH3)2CdCl4, which belongs to the organic–inorganic hybrid layered compounds, was synthesized as an example of long-chain complexes of the series (n-CnH2n+1NH3)2CdCl4 (n = 8–18). The ac conductivity σac(ω, T) and the complex dielectric permittivity ε*(ω, T) were extensively investigated as a function of both frequency (5–100 kHz) and temperature (100 K < T < 400 K). The general trend of the mentioned parameters indicates that the frequency dependent conductivity behaves according to the power law, namely σac(ω, T) α ωs(ω, T) where s is the frequency exponent (0 < s < 1). Furthermore, the differential scanning calorimetric chart and the differential thermal analysis thermogram were performed. The combination of thermal and electrical parameters confirms the existence of two main structural phase transitions of the first-order type at T ≈ 360.70 K (minor) and at T ≈ 350.70 K (major) in addition to two intermediate phases with a transition temperature at T ≈ 353.75 K. (The major transition precedes the minor one.) Different conduction mechanisms and the universality of ac conduction were discussed. The nature of each detected phase transition has been explained on the basis of the most recent crystal structure and particularly the role of the N–HCl hydrogen bonding as a trigger force for phase transitions.