{"title":"Effects of radius and electronegativity of donors on the microstructure and mechanical, thermal, and electrical properties of ZnO varistors","authors":"Bo-wen Wang, Jia-zheng Lu, Peng-zhao Gao, Zhi-yao Fu, Zheng-long Jiang, Wei-wei Gong","doi":"10.1007/s10832-024-00349-x","DOIUrl":null,"url":null,"abstract":"<div><p>In this paper, influence of radius and electronegativities of seven kinds of donors on the composition, microstructure, mechanical, thermal and electrical properties of ZnO varistors were investigated via XRD, SEM, XPS, mechanical, thermal and electrical properties tests. Results showed that when sintered at 1100 °C for 2 h, the obtained varistors exhibited a dense microstructure, where radius of donors played an important role on the grain size and size distribution of varistors; Mechanical properties and coefficient of thermal expansion of varistors were mainly affected by the radius of donors, with specimen 6# possessing the highest values of 123.46 MPa (σ<sub>f</sub>), 80.47 GPa (<i>E</i><sub><i>f</i></sub>), and 6.58 × 10<sup>−6</sup> °C<sup>−1</sup> (<i>λ</i><sub><i>c</i></sub>), respectively; Values of<i> E</i><sub><i>1mA</i></sub> and α initially increased and then decreased with the increase of donors’ radius, whereas those of <i>J</i><sub><i>L</i></sub> and <i>K</i> exhibited opposite trends. <i>E</i><sub><i>1mA</i></sub> and α had maximum values of 569.94 V mm<sup>–1</sup> and 26.70, whereas <i>J</i><sub><i>L</i></sub> and <i>K</i> possessed the lowest values of 2.31 μA⋅cm<sup>−2</sup> and 1.35, respectively, when Co<sup>2+</sup> worked as the donor (specimen 6#). The DC aging process of ZnO varistors obeyed the ion migration mechanism, the radius of donors can affect the number of it entering the ZnO lattice, which can limit the migration of zinc gaps via the formation of substitution and filling defects in the ZnO lattice. The electronegativity of donors can reduce the ion migration speed via the stronger electrostatic force, and specimen 6# possessed the lowest DC aging properties (<i>K</i><sub><i>T</i></sub> = 1.68).</p></div>","PeriodicalId":625,"journal":{"name":"Journal of Electroceramics","volume":"52 1","pages":"83 - 102"},"PeriodicalIF":1.7000,"publicationDate":"2024-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Electroceramics","FirstCategoryId":"88","ListUrlMain":"https://link.springer.com/article/10.1007/s10832-024-00349-x","RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATERIALS SCIENCE, CERAMICS","Score":null,"Total":0}
引用次数: 0
Abstract
In this paper, influence of radius and electronegativities of seven kinds of donors on the composition, microstructure, mechanical, thermal and electrical properties of ZnO varistors were investigated via XRD, SEM, XPS, mechanical, thermal and electrical properties tests. Results showed that when sintered at 1100 °C for 2 h, the obtained varistors exhibited a dense microstructure, where radius of donors played an important role on the grain size and size distribution of varistors; Mechanical properties and coefficient of thermal expansion of varistors were mainly affected by the radius of donors, with specimen 6# possessing the highest values of 123.46 MPa (σf), 80.47 GPa (Ef), and 6.58 × 10−6 °C−1 (λc), respectively; Values of E1mA and α initially increased and then decreased with the increase of donors’ radius, whereas those of JL and K exhibited opposite trends. E1mA and α had maximum values of 569.94 V mm–1 and 26.70, whereas JL and K possessed the lowest values of 2.31 μA⋅cm−2 and 1.35, respectively, when Co2+ worked as the donor (specimen 6#). The DC aging process of ZnO varistors obeyed the ion migration mechanism, the radius of donors can affect the number of it entering the ZnO lattice, which can limit the migration of zinc gaps via the formation of substitution and filling defects in the ZnO lattice. The electronegativity of donors can reduce the ion migration speed via the stronger electrostatic force, and specimen 6# possessed the lowest DC aging properties (KT = 1.68).
期刊介绍:
While ceramics have traditionally been admired for their mechanical, chemical and thermal stability, their unique electrical, optical and magnetic properties have become of increasing importance in many key technologies including communications, energy conversion and storage, electronics and automation. Electroceramics benefit greatly from their versatility in properties including:
-insulating to metallic and fast ion conductivity
-piezo-, ferro-, and pyro-electricity
-electro- and nonlinear optical properties
-feromagnetism.
When combined with thermal, mechanical, and chemical stability, these properties often render them the materials of choice.
The Journal of Electroceramics is dedicated to providing a forum of discussion cutting across issues in electrical, optical, and magnetic ceramics. Driven by the need for miniaturization, cost, and enhanced functionality, the field of electroceramics is growing rapidly in many new directions. The Journal encourages discussions of resultant trends concerning silicon-electroceramic integration, nanotechnology, ceramic-polymer composites, grain boundary and defect engineering, etc.