Analysis of Stress and Strain in ZnO Nanoparticle-Bi2O3-Mn2O3 Varistor Ceramics at Different Annealing Temperatures

Abstract

The stress and lattice constants in zinc oxide (ZnO) nanoparticles play a major role in determining the distortions that occur in the crystal during the preparation of the sample as a result of exposure to several factors, such as external strain, temperature, pressing, and structural defects (oxygen vacancies and zinc/oxygen interstitials). 20 nm zinc oxide nanoparticles were used to make high-density ZnO discs doped with Bi2O3and Mn2O3via uniaxial pressing at 4 ton/cm2and sintering at 1200 °C for 1 h. Structural, elemental, and optical characterizations were then performed on the samples using various techniques. High-oxygen thermal annealing significantly affected the varistor, particularly in enhancing the growth of the grain even at a low annealing temperature (400 °C). The strong solid-state reaction during annealing may be attributed to the high surface area of the 20 nm ZnO nanoparticles that exhibited a strong surface reaction even at low annealing temperatures. The annealing treatment also improved the grain crystallinity, as shown by the transition of the intrinsic compressive stress to tensile stress based on the XRD lattice constant and full-width at half-maximum data. Therefore, high-oxygen thermal annealing can be used as a new technique in controlling the stress in ZnO nanoparticle-Bi2O3-Mn2O3based varistors with improved structural and optical properties.