Non-ohmic characteristics of ZnO-V2O5 ceramics

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Abstract
The densification behavior, microstructure, and electrical properties of ZnO‐V2O5 ceramics were studied with V2O5 as the only additive ranging from 0.01 to 1.0 mol %. The addition of V2O5 to zinc oxide shows a tendency to enhance the densification rate and promote grain growth. However, a microstructure that consisted of anomalously grown grains was found for the specimens containing V2O5≥0.05 mol % when sintered at 1100 °C for 2 h. The x‐ray diffraction and SEM‐EDS microanalysis revealed that the sintered specimens had a two‐phase microstructure, i.e., a vanadium‐rich intergranular phase formed between ZnO grains. The formation of the grain boundary barrier layer was confirmed by the non‐ohmic I‐V behavior and the quick drop of apparent dielectric constant with increasing frequency of the ceramics. A nonlinearity coefficient of 2.4–2.8 was obtained at a current density of 10 mA/cm2 for a series ZnO‐V2O5 ceramics, and a Schottky barrier height of 0.44–0.47 eV (at 25 °C) was determined from the I‐V and C‐V experimental data, based on the thermionic emission theory, and the model of back‐to‐back double Schottky barriers.

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