Preparation of Pseudotetragonal ZrO_0.75S and Its Electric Responses on Temperature and Frequency Related to Microstructural Relaxation

摘要

Pseudotetragonal ZrO_0.75S whose space group is P2₁2₁2₁ was synthesized and the cell dimensions were a=5.110(2) ∈, b=5.110(7) ∈, and c=5.198(8) ∈. The space group P2₁2₁2₁ seems to be resulted from lowering the symmetry of cubic ZrOS structure with P2₁3 space group by lattice distortion due to the oxygen defects. In the distorted structure, bond shortening between metal-nonmetal by reduction of cell volume and alternation of Zr-Zr distance were observed. Dielectric constant and loss data of the bulk material in temperature range -170 to 20 ∩ and frequency range 50 Hz to 1 MHz showed that there was dielectric transition at around -70 ∩ originated from the relaxation of Zr-S segment. Comparing with ZrO₂ exhibited the dielectirc constants, 9.0 at room temperature, ZrO_0.75S showed high dielectric constant, k = 200.2 at 100 kHz. The activation energy of relaxation time due to dielectric relaxation of Zr-S was 0.47 eV (11.3 kcal/mole). According to the impedance spectra, ZrO_0.75S showed more parallel circuit character between the resistance and capacitance components at the temperature (-70 ∩) that the Zr-S dielectric relaxation was observed.