Nonlinearity Characteristics of Low-Voltage Barium Titanate Based Zinc Oxide Varistor Ceramics Modified by Cobalt Dopants


  • Shaifudin Muhamad Syaizwadi
  • Mohd Sabri Mohd Ghazali Advanced Nano Materials (AnoMa) Research Group, Nano Research Team, Faculty of Science and Marine Environment, Universiti Malaysia Terengganu, 21030 Kuala Nerus, Terengganu, Malaysia
  • Wan Mohamad Kamaruzzaman Wan Mohamad Ikhmal
  • Mohd Anuar Muhamad Syahmi Hazim
  • Wan Abdullah Wan Rafizah
  • Syara Kassim
  • Oon Jew Lee
  • Ismail Nur Quratul Aini
  • Sa’at Nor Kamilah
  • Mohd Hafiz Mohd Zaid
  • Mohd Fekeri Fazira Maria
  • Khamirul Amin Matori



ZnO varistors, barium titanate, Co3O4, grain boundary, electrical properties


Application of ZnO varistor at low voltage has increased significantly due to the high demands of low-voltage electronics with high nonlinearity characteristics and low leakage current. The varistor ceramics were developed via solid-state reaction method and the resultant sample was analyzed by means of SEM, EDS and XRD. The nonlinearity characteristics of ZnO varistor ceramics for different contents of cobalt oxide (Co3O4) at a given barium titanate (BaTiO3) amount were analyzed based on the J-E characteristics measurement. The increased value of nonlinear coefficient (α) equal to 4.8 was exhibited by the sample made with 12 wt.% BaTiO3 additive. As the concentration of dopant (Co3O4) incorporated was increased from 0.5 to 1.5 wt.%, the varistor voltage limit decreased from 8.9 V/mm to 7.0 V/mm, respectively. Additionally, the barrier height increased from 0.88 to 0.98 eV for 0.0 wt.% to 1.0 wt.% of Co3O4 concentration, respectively. The highest α of 7.2 was obtained at 0.5 wt.% Co3O4 and decreased with further doping content due to to the reduction of barrier height caused by the variation of electronic state at the grain boundaries.