The varistor system SnO 2 ·CuO·Ta 2 O 5 with different Ta 2 O 5 dopants sintered at 1300˚C for 80 min was investigated. It is found that Ta 2 O 5 significantly affects the grain size and the electrical properties. The average grain size decreases from 6.8 to 1.9 µm with an increase in Ta 2 O 5 concentration from 0.05 to 1.00 mol%. The sample with 0.05 mol% Ta 2 O 5 has the best nonlinear electrical property and the highest nonlinear coefficient (α = 37.9) and the sample with 0.50 mol% Ta 2 O 5 possesses the highest densification (98.7% of the theoretical density) among all the samples. The reason for the nonlinearity of SnO 2 ceramics is explained.

Erasable memory devices are fabricated by the combination of a conducting polymer and solid polymer electrolyte. The former is used as a memory channel and the latter as an electrolyte medium. The channel conductivity can be controlled over 3‐4 orders of magnitude by electrochemical doping through a writing electrode. The response time, depending on the writing voltage, is several seconds. The characteristics of the memory device are discussed.