Preparation and electrical properties of ZnO–glass ceramic films

Abstract

ZnO–glass ceramic films doped with Sb 2O 3, MnO, Co 2O 3 and Cr 2O 3 were fabricated by a novel sol–gel process. The precursors were prepared by dispersing the ZnO nano-powders throughout into the sols, which were prepared by dissolving zinc acetate dihydrate and the dopants into 2-methoxyethanol and stabilized by diethanolamine and glacial acetate. The films were prepared on Au/Si substrates by spin coating method and were heat-treated and annealed in air at 450 and 750 °C, respectively. The films with the thickness of about 2 μm were obtained after 10–20-layers deposition. The crystal phases, the residual stress in the crystals and the microstructure of films were studied via XRD analysis, Raman spectroscopy and SEM, respectively. The films were used as film varistors after the upper Au electrodes, the area of which is 3 mm 2, were made on the surface of the films by vacuum evaporation. The electrical properties were studied by varistor characteristics testing instrument, and the remarkable nonlinear V– I response was observed. The nonlinear voltage and the nonlinear coefficient ( α), which were 3–19 V and 5–15, respectively, were affected obviously by glass content. The highest nonlinearity coefficient with nonlinear voltage of 6.5 V could be achieved when the films contain 8 wt% glass.