Er ₂ O ₃ Doping Effect on Electrical Properties of ZnO – V ₂ O ₅ – MnO ₂ – Nb ₂ O ₅ Varistor Ceramics

Abstract

The microstructure and electrical properties of Er 2 O 3 ‐doped ZnO – V 2 O 5 – MnO 2 – Nb 2 O 5 varistor ceramics were investigated with different contents of Er 2 O 3 . Increasing content of Er 2 O 3 increased the sintered density (5.51–5.61 g/cm 3 for Er 2 O 3 ‐doped samples) and reduced the average grain size (5.2–5.7 μm). With increasing content of Er 2 O 3 , the breakdown field increased from 4800 to 5444 V/cm up to 0.05 mol%, whereas a further increase decreased it. The maximum nonlinear coefficient was 63, which was from the addition of 0.05 mol% Er 2 O 3 . The donor concentration increased from 4.21 × 10 17 to 1.04 × 10 18 cm −3 with increasing content of Er 2 O 3 and the barrier height exhibited a maximum value (1.21 eV) at 0.05 mol% Er 2 O 3 .