College of Science, Wuhan University of Science and Technology, Wuhan 430081, China;
Department of Physics, East China Normal University, Shanghai 200062, China;
Department of Physics, East China Normal University, Shanghai 200062, China;
Department of Physics, East China Normal University, Shanghai 200062, China;
inorganic materials; electrical properties; high-energy ball milling; varistor; microstructure; low-temperature sintering; zinc oxide; yttrium oxide;