[2] [2] PIANARO S A, BUENO P R, LONGO E, et al.A new SnO2-based varistor system［J］.J Mater Sci Lett, 1995, 14(10): 692-694.

[3] [3] METZ R, KOUMEIR D, MOREL J, et al.Electrical barriers formation at the grain boundaries of Co-doped SnO2 varistor ceramics［J］.J Eur Ceram Soc, 2008, 28(4):829-835.

[4] [4] YONGVANICH N, NIYOMTRUM K, CHAIRATANASET C, et al.Enhancement of non-linear properties in SnO2 varistors by ZnO doping［J］.Ceram Int, 2017, 43(1):280-285.

[5] [5] LIU D J, WANG W Q, WANG F, et al.High nonlinear coefficient SnO2 varistors tailored by Mn2O3 doping［J］.Mat Sci Semicon Proc, 2020, 117:105160.

[6] [6] HE J F, PENG Z J, FU Z Q, et al.Effect of ZnO doping on microstructural and electrical properties of SnO2-Ta2O5 based varistors［J］.J Alloy Compd, 2012, 528:79-83.

[7] [7] BUONOCORE A L W, MOUTA R, GOMES J C, et al. Varistor behavior in a ternary system based on SnO2 doped with a hexavalent donor:SnO2-MnO2-WO3［J］.J Alloy Compd, 2019, 811:151538.

[8] [8] MUKAE K, TSUDA K, NAGASAWA I. Capacitance-vs-voltage characteristics of ZnO varistors［J］.J Appl Phys, 1979, 50:4475-4476.

[9] [9] WURST J C, NELSON J A.Lineal intercept technique for measuring grain size in two-phase poly crystalline ceramic ［J］.J Am Ceram Soc, 1972, 55(2):109-111.

[10] [10] FAYAT J, CASTRO M S.Defect profile and microstructural development in SnO2-based varistors［J］.J Eur Ceram Soc, 2003, 23(10):1585-1591.

[11] [11] BUENO P R, ORLANDI M O, SIMES L G P, et al. Nonohmic behavior of SnO2-MnO polycrystalline ceramics I.correlations between microstructural morphology and nonohmic features［J］.J Appl Phys, 2004, 96(5):2693-2700.

[12] [12] OSAMA, DESOUKY A, RADY K E.Synthesis, structure and dielectric properties of nanocrystalline SnO2-CoO-Nb2O5 varistor doped with Cr2O3［J］.J Mater Sci: Mater Electron, 2017, 28:4197-4203.

[14] [14] MARGIONTE M A L, SIMES A Z, RICCARDI C S, et al.Nonlinear characteristics of Cr2O3, WO3, ZnO and CoO doped SnO2 varistors［J］.Mater Lett, 2006, 60(1):142-146.

[15] [15] SAKAGUCHI I, SAKAMOTO N, HASHIGUCHI M, et al.Characterization of oxygen defect and zinc segregation in the dense tin dioxide ceramics added with zinc oxide［J］.J Ceram Soc Japan, 2013, 121(1419): 956-959.

[16] [16] FOSCHINI C R, PERAZOLLI L, VARELA J A. Sintering of tin oxide using zinc oxide as a densification aid ［J］.J Mater Sci, 2004, 39(18):5825-5830.

[17] [17] SAADEDDIN I, HILAL H S, PECQUENARD B, et al. Simultaneous doping of Zn and Sb in SnO2 ceramics: enhancement of electrical conductivity［J］.Solid State Sci, 2006, 8(1):7-13.