EFFECT OF COPPER ADDITIVE ON THE MICROSTRUCTURE AND ELECTRICAL-PROPERTIES OF POLYCRYSTALLINE ZINC-OXIDE

Nonohmic behavior is obtained for polycrystalline ZnO with copper as the only additive in the range 0.3 less-than-or-equal-to x less-than-or-equal-to 1 wt%. The effect of copper on the microstructure and electrical behavior of ZnO:Cu ceramics is investigated. The leakage current decreases and the breakdown electric field increases as the copper concentration increases. The large apparent dielectric constant of ZnO:Cu ceramic (k > > k(ZnO), k(ZnO) is the dielectric constant of pure ZnO) is attributed to the grain boundary barrier layer effect. A Schottky barrier height of 0.27-0.46 eV is obtained for various copper-added samples, depending on sintering temperatures.