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<p>Achieving a zinc oxide-based varistor with minimal bismuth oxide evaporation and a uniform microstructure containing well-distributed spinel phases remains a considerable challenge. Compared with microscale powders, using raw materials with nanoscale dimensions and uniform distribution can enhance the final electrical and mechanical properties of varistors. This study investigates the effect of reducing the particle sizes of antimony oxide and bismuth oxide on the microstructural, mechanical, and electrical properties of zinc oxide-based varistors. Fine-ball bead milling was employed to reduce particle sizes via a wet milling process. Slurries containing powders of varying particle sizes were prepared, followed by granulation, uniaxial pressing, and a two-stage sintering process to fabricate the varistor samples. Slurry density, particle size distribution, and viscosity were evaluated, while granule compressibility was used to assess density–mechanical strength relationships. X-ray diffraction and scanning electron microscopy characterized the composition and microstructure, and electrical measurements determined the nonlinear coefficient, breakdown voltage, and leakage current density. Results revealed an 85% reduction in bismuth oxide particle size and a 44% reduction in antimony oxide, without significant changes in slurry density, while viscosity decreased by approximately 50% when transitioning from micrometric to nanometric systems. Granule strength increased by 19% and 37% for bismuth oxide and antimony oxide, respectively. Zinc oxide crystallite size in the varistor microstructure decreased by 63% and 90%. Reducing initial particle sizes also enhanced final density and produced a finer, more uniform microstructure. Electrical performance improved, with a 15% increase in the nonlinear coefficient, a 50% reduction in leakage current density, and a 30% increase in breakdown voltage. Overall, combining nanoscale particle sizes with reduced sintering temperature and duration effectively minimized bismuth oxide evaporation and promoted uniform spinel-phase formation.</p>

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Investigation of microstructural, electrical, and mechanical properties of zinc oxide-based varistor containing micro/nanoparticles of bismuth and antimony oxides produced by two-step sintering

  • 期刊论文

  • 发表日期：

    2026年6月29日

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  • Leila Jamshidi Bakhtar,
  • Hassan Abdoos

摘要

Achieving a zinc oxide-based varistor with minimal bismuth oxide evaporation and a uniform microstructure containing well-distributed spinel phases remains a considerable challenge. Compared with microscale powders, using raw materials with nanoscale dimensions and uniform distribution can enhance the final electrical and mechanical properties of varistors. This study investigates the effect of reducing the particle sizes of antimony oxide and bismuth oxide on the microstructural, mechanical, and electrical properties of zinc oxide-based varistors. Fine-ball bead milling was employed to reduce particle sizes via a wet milling process. Slurries containing powders of varying particle sizes were prepared, followed by granulation, uniaxial pressing, and a two-stage sintering process to fabricate the varistor samples. Slurry density, particle size distribution, and viscosity were evaluated, while granule compressibility was used to assess density–mechanical strength relationships. X-ray diffraction and scanning electron microscopy characterized the composition and microstructure, and electrical measurements determined the nonlinear coefficient, breakdown voltage, and leakage current density. Results revealed an 85% reduction in bismuth oxide particle size and a 44% reduction in antimony oxide, without significant changes in slurry density, while viscosity decreased by approximately 50% when transitioning from micrometric to nanometric systems. Granule strength increased by 19% and 37% for bismuth oxide and antimony oxide, respectively. Zinc oxide crystallite size in the varistor microstructure decreased by 63% and 90%. Reducing initial particle sizes also enhanced final density and produced a finer, more uniform microstructure. Electrical performance improved, with a 15% increase in the nonlinear coefficient, a 50% reduction in leakage current density, and a 30% increase in breakdown voltage. Overall, combining nanoscale particle sizes with reduced sintering temperature and duration effectively minimized bismuth oxide evaporation and promoted uniform spinel-phase formation.