# Tailoring morphological and electrical properties of nanoplate-ZnO varistors via sintering temperature

## TL;DR

This study shows how adjusting the sintering temperature of ZnO nanoplate varistors can improve their electrical and mechanical properties for high-voltage applications.

## Contribution

The novel contribution is demonstrating that ZnO nanoplate varistors sintered at 1100°C achieve optimal electrical performance with high nonlinearity and low leakage current.

## Key findings

- Sintering at 1100°C produced varistors with high nonlinearity (α = 48.5), low leakage current (JL = 9.7 μA cm−2), and high breakdown threshold (Eb = 689 V mm−1).
- Increasing sintering temperature increased grain size and hardness but caused 17–19% shrinkage.
- Grain boundary resistivity at low frequencies matched DC resistivity at low electric fields.

## Abstract

In this study, ZnO nanoplates (crystallite size: 100 nm, thickness: 15 nm) were synthesized via a hydrothermal route. Varistors were then fabricated using these ZnO nanoplates incorporated with five oxide dopants (Bi2O3, Sb2O3, MnO2, Co3O4, and Cr2O3) and sintered at 1000, 1100, and 1200 °C. A control varistor sample using micro-sized ZnO was also prepared. The effects of sintering temperature on the structural, mechanical, and electrical properties of ZnO-based varistors were systematically studied. Increasing the sintering temperature from 1000 °C to 1200 °C enlarged the grain size (1.7–6.8 μm), enhanced hardness (200–280 HV), and resulted in 17–19% shrinkage. At 1100 °C, the varistor achieved a balance of high nonlinearity (α = 48.5), low leakage current (JL = 9.7 μA cm−2), and high breakdown threshold (Eb = 689 V mm−1). Impedance analysis showed a resistive–capacitive transition at higher frequencies, while grain boundary resistivity at low frequencies (106.5–108 Ω m) aligned with DC resistivity at the low applied electric fields. These results highlight the advantages of ZnO nanoplates in enhancing the electrical performance of varistors, making them promising for high-voltage applications.

ZnO nanoplate-based varistor doped with Bi2O3, Sb2O3, MnO2, Co3O4, and Cr2O3, sintered at 1100 °C, shows optimal properties: uniform grains, high hardness, low leakage current, and high nonlinearity.