Impedance spectroscopic studies, dielectric properties and microstructure of rutile type chromium niobate CrNbO4

Rutile type chromium niobate, CrNbO4 (CN), was synthesized by solid state reaction (CN-SSR) and sol-gel (CN-SG900) methods. The relative density of CN-SG900 was further improved by calcination at 1150 °C for 24 h (CN-SG1150). Scanning electron microscopic analysis showed the differences in the microstructures of these samples. The measured dielectric constants (@100 Hz) are 381, 1323 and 2973 for CN-SG900, CN-SG1150 and CN-SSR, respectively. A decrease in dielectric constant with increasing frequency in these samples revealed the presence of Maxwell-Wagner type interfacial polarization. The different dielectric behaviors of CN-SG900, CN-SG1150 and CN-SSR are related to the microstructural differences among conducting grains and resistive grain boundaries that contribute to the dielectric relaxation in these materials.