Impact of sintering temperatures on conduction behaviors of ZnO nanoparticles- and MnO-doped SnO2-based thick film varistors obtained by screen printing

Abstract

In this study, ZnO nanoparticles and MnO-doped SnO2-based thick film varistors (TFVs) were fabricated using screen printing technique. The sintering temperature had significant impact on the SZM-based TFVs, especially in terms of grain growth, even at a low sintering temperature of 1100[Formula: see text]C. The strong solid-state reaction during sintering may be attributed to the large surface area of the 20 nm ZnO nanoparticles that promoted strong surface reaction even at low sintering temperatures. Moreover, the X-ray diffraction lattice constant and full wave at half maximum data indicated that the sintering process also improved the grain crystallinity with the decrease in intrinsic compressive stress. The sintering temperatures also significantly influenced the electrical properties of the SZM-based TFVs with a significant decrease in the breakdown field from 360 V/mm (sample at 1100[Formula: see text]C) to 158 V/mm (sample at 1250[Formula: see text]C). The grain boundary resistance ([Formula: see text] also experienced a dramatic drop from 266.4 k[Formula: see text] (sample at 1100[Formula: see text]C) to 89.46 k[Formula: see text] (sample at 1250[Formula: see text]C). The sample sintered at 1200[Formula: see text]C exhibited superior electrical behaviors with a nonlinear exponent of 61 and leakage current of 115 [Formula: see text]A. Furthermore, it achieved high permittivity and low dissipation factor at the low frequency range. The conduction behaviors of [Formula: see text] ions with activation energy of approximately 0.6 eV was dominated by decreasing [Formula: see text] and [Formula: see text] defects (around 0.4 eV) with increasing sintering temperature. Therefore, the sintering process can be applied to control the conduction behaviors of SZM-based TFVs doped with ZnO nanoparticle powder and achieve improved structural and electrical properties with good nonlinear behaviors.