Study of thermal, structural and impedance characteristics of nanocrystalline copper chromite synthesized via hydrothermal process

Nanocrystalline copper chromite (CuCr2O4) spinel oxide was prepared by hydrothermal method. X-ray diffraction results showed that single-phase tetragonal copper chromite was obtained after calcination at 800 A degrees C for 4 h. This phase was also confirmed by Rietveld refinement study with lattice parameters of a = b = 6.0336 , c = 7.8265 and space group of I-4 2D. Thermogravimetric analysis showed an overall mass loss of about 24 %. This was due to evaporation of adsorbed water and decomposition of chromium and copper hydroxides to form copper chromite (CuCr2O4). Differential scanning calorimetric analysis indicated the commencement of crystallization at 417 A degrees C. Thermal study revealed that CuCr2O4 was thermally stable above 800 A degrees C. FESEM revealed that the grain size of CuCr2O4 increased with increase in sintering temperature, and well-defined fine octahedron-like crystals of CuCr2O4 were obtained after sintering at 1050 A degrees C for 4 h. Impedance spectroscopy was performed and an equivalent circuit model (R (1) Q (1)) (R (2) Q (2)) was fitted to explain two electroactive regions associated with grains and grain boundaries in CuCr2O4 oxide material. Frequency-dependent conductivity and dielectric constant of the material showed increasing and decreasing trends, respectively.