Synthesis by Hydrothermal Treatment of ZnO-Based Varistors Doped with Rare Earth Oxides and Their Characterization by Impedance Spectroscopy

Abstract

ZnO-based ceramic varistors have shown excellent electrical and dielectric properties due to their characteristics microstructures represented by the arrangement of their grains and grain boundaries that allow the absorption and flow of energy when subjected to an electrical surge. Their properties and characteristics depend on their chemical compositions and processing routes. Typical processing routes involve several stages of grinding and precalcination—which are time consuming processes. Because of this, this study proposes a simpler and cheaper alternative route for processing ceramic varistors. The alternative process proposed is the mixing of the precursor oxides by means of a hydrothermal treatment. The characteristics and properties of the synthesized ceramic varistors were evaluated by means of scanning electron microscopy, X-ray diffraction and impedance spectroscopy, considering the effect of the addition of rare earth oxides (La2O3, CeO2 and Nd2O3). The results showed that the mixing of the oxides through hydrothermal treatment produces ceramic varistors with characteristics and properties similar to those obtained by other processing routes. Furthermore, it was observed that the addition of rare earth oxides affects the characteristics and properties of the ceramic varistor depending on the type of rare earth oxide added, its concentration and ionic radius.

Effects of Dopants and Processing Parameters on the Properties of ZnO-V2O5-Based Varistors Prepared by Powder Metallurgy: A Review

“…The liquid-phase methods include sol–gel methods [ 85 , 86 ], the precipitation or coprecipitation and subsequent calcination of powders [ 70 ], hydrothermal methods [ 87 , 88 ], atomization and spray drying, and flame spray pyrolysis [ 89 ]. These methods can yield reasonable control of the content and shape of MOV powders.…”

“…Similar findings were observed in ZnO-V 2 O 5 -based systems doped with other REOs, such as Y 2 O 3 , Sm 2 O 3 , Nd 2 O 3 , Dy 2 O 3 , Yb 2 O 3 , Gd 2 O 3 , etc. [ 27 , 44 , 87 , 173 , 181 ], sintered under comparable conditions. All REOs gradually inhibited the growth of ZnO grains during sintering and hindered the densification of MOVs with an increase in the content of REOs and RE-related secondary phases, as well as with an increase in sintering temperature.…”

“…Preparation methods of EMO and MOV powders, along with their advantages and disadvantages[54,70,[85][86][87][88][89][90][91][92].…”

Valor diagnóstico de la ultrasonografía en la detección del cáncer de mama en el Instituto Nacional de Enfermedades Neoplásicas, Lima 2021

“…Para Porcayo et. al (2018), las pacientes con carcinoma de mama triple negativo entre las edades de 40 y 49 años de edad demostraron en los resultados que el ultrasonido tiene una sensibilidad de 92% para la detección de la neoplasia de mama.…”