Study of phase transition in a [CdHgI₄ : 0.2AgI] mixed conducting composite system doped with KI and K₂SO₄

Abstract

Newcomposite superionic systems, [CdHgI 4 : 0.2AgI] : 0.xKI and [CdHgI 4 : 0.2AgI] : 0.xK 2 SO 4 (x ¼ 0.2, 0.4, 0.6 mol. wt%), were prepared, using [CdHgI 4 : 0.2AgI] mixed composite system as the host. Electrical conductivity was measured to study the transition behavior at frequencies of 100 Hz, 120 Hz, 1 kHz, and 10 kHz in the temperature range from 150 C to 250 C using a GENRAD 1659 RLC Digibridge. A sharp increase in conductivity was observed during ! phase transition. Upon increasing the dopant-to-host ratio, the conductivity of the superionic systems exhibited Arrhenius (thermally activated)-type behavior. Differential thermal analysis, differential scanning calorimetry, thermogravimetric analysis, and X-ray powder diffraction were performed to confirm the doping effect and transition in the host. The phase transition temperature increased with an increase in the dopant concentration. Activation energies in eV for pre-and post-transition phase behavior are reported.

A new nanocomposite superionic system (CdHgI4/HgI2): Synthesis, characterization and experimental investigation

“…Where σ o is the pre-exponential-factor of the ionic conductivity, k the Boltzmann constant, T the absolute temperature and E a is the activation energy for the ionic conductivity. The log σT vs. 1/T plot shift from a lower temperature to a high temperature is responsible for the phase change of CdHgI 4 and is associated with a charge transfer process between electron levels of Hg, Cd and I [24].…”