Investigation of dielectric relaxation and degradation behavior of two-step sintered ZnO varistors

Fu, Zhiyao; He, Junjia; Lu, Jiazheng; Fang, Zhen; Wang, Bowen

doi:10.1016/j.ceramint.2019.07.201

Cited by 26 publications

(8 citation statements)

References 38 publications

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“…When the addition of Ga2O3 exceeded 0.04 mol%, some additives may existed in the grain boundary of ZnO crystal to inhibit ZnO grain growth and reduce the density of the ZnO varistors [4] . -Bi2O3 (JCPDS no.78-1793), and -Bi2O3 (JCPDS no.76-2478) were detected in ZnO varistors regardless of Ga2O3 amount, similar to the findings of Fu [1] and Zhao [4] . The Ga2O3 phase was not observed in the specimens, which can be attributed to the small amount [4] .…”

Section: Influences Of Sintering Process On the Composition And Microsupporting

confidence: 81%

“…These disks were sintered at different temperatures and holding time at a heating rate of 4 °C•min -1 and a cooling rate of 2 °C•min -1 in air. After sintering, the upper and lower surfaces of ZnO varistor samples were polished and then covered with silver paste, and then these samples were heated at 600 °C for 10 min in air to form electrodes [1] .…”

Section: Preparation Of the Ga2o3 Doped Zno Based Varistorsmentioning

confidence: 99%

“…Microstructure of ZnO based varistor was examined via scanning electron microscopy (SEM, Regulus 8100, Hitachi, Japan) when the surface of specimen was pre-polished and glass phase was removed via etching method [1] .…”

Section: Characterization Of the Ga2o3 Doped Zno Based Varistorsmentioning

confidence: 99%

“…The electric field-current density (E-J) characteristic of ZnO based varistor was obtained via a source measurement unit (Keithley 2410, USA). The voltage gradient (E1mA) is the breakdown voltage at a unit height, and the leakage current (JL) is determined at 0.75 U1mA, the nonlinear coefficient (α) is defined by Eq(1) [1] :…”

Section: Characterization Of the Ga2o3 Doped Zno Based Varistorsmentioning

confidence: 99%

“…ZnO varistors are a typical polycrystalline ceramic obtained by sintering ZnO powder with minor primary additives, such as Bi2O3, Pr6O11 and V2O5 [1][2][3] , and secondary additives such as Sb2O3, SiO2, Co2O3, MnO2, Al2O3, Cr2O3, Ni2O3, Ga2O3, and In2O3 [4,5] , it mainly works as a surge-protection device and is extensively applied in electronic and electrical systems to limit overvoltage [6, 7,] . Therefore, voltage gradient of ZnO varistors is an important parameter for evaluating the performance of ZnO varistors, which can be improved through sintering modification [1,8,9] , particle-size choice [6] , and composition design [3][4][5]10,11] . For these three protocols, improving the electrical properties via composition design possesses the advantages of easy operation, wide adjustment of electrical properties, and excellent comprehensive properties of the obtained varistors, among others.…”

Section: Introductionmentioning

confidence: 99%

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Synchronously Improved Voltage Gradient and Mechanical Properties of ZnO Based Varistor by Doping Ga2O3

Wang¹,

Chen

Gao

et al. 2020

Preprint

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ZnO based varistors with high voltage gradient and excellent mechanical and thermal properties were fabricated by Ga2O3 doping and using nanoparticles. The compositions and microstructure of the varistors, as well as their electrical, mechanical and thermal properties were investigated by XRD, XPS, SEM, E-J, C-V, mechanical and thermal expansion measurements. Also, the mechanism of Ga2O3 addition on electrical and mechanical properties of the varistors was discussed detailedly. Results showed that the added Ga2O3 preferentially occupied the lattice position of ZnO crystal through the formation of a substitutional solid solution (Donor doping), they then occupied the void position through the formation of an interstitial solid solution (Acceptor doping), in which residual Ga2O3 existed in the grain boundary and served as inversion boundaries. The formation of the substitutional and interstitial solid solutions helped to improve the electrical properties, when the Ga2O3 content was 0.40 mol%, E1mA, α and K were 1235.00 V·mm− 1, 46.0 and 1.37, respectively, being due to the small particle size and the relative content of donor, acceptor and grain boundary in ZnO grain; The increased content of inversion boundaries stimulated the abnormal growth of ZnO grain, and the formed plate-like grain helped to improve the mechanical properties and thermal expansion coefficient of the varistors, values of σf, Ef, and KIC reached 147.43 MPa, 213.61 GPa and 2.05 MPa·m1/2, showing improvements of 25.29%, 47.67%, and 38.51%, respectively, compared with those of ZnO varistors without Ga2O3.

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