Effect of Ag Electrode on the Electrical Properties of SrTiO3-Based Ring Varistors

The effect of two Ag electrodes on the electrical properties of SrTiO
₃
ring varistors were presented in this paper. It was found that one of them results in ohmic contact while the other results in non-ohmic contact between electrode and ceramics. Compared with the results achieved by using of In-Ga alloy paste, non-ohimic contact lead to larger varistor voltage U
_10mA
, larger nonlinear coefficient alpha and lower dielectric loss tandelta. SEM technique was applied to investigate the interface of Ag electrode/SrTiO
₃
ceramics. A 30-40 mum wide layer, mainly composed of Zn element, was found between ohmic Ag electrode and ceramics, which is the origin of ohmic contact between electrode and SrTiO
₃
ceramics