The effect of humidity on the voltage–current characteristic of SnO2 based ceramic varistor

Current limiting and negative differential resistance in indium oxide based ceramics

“…The current limiting effect observed in the In 2 O 3 -Bi 2 O 3 ceramics studied here is markedly different from the electrical properties of ZnO-Bi 2 O 3 -based [20,22] or SnO 2 -Bi 2 O 3 -based ceramics [21,23,24], which exhibit the varistor effect. In both groups of materials the grain-boundary barriers play the main role in the conduction process.…”

“…Indium oxide based ceramics (mol.%) 95In 2 O 3 -5Bi 2 O 3 were prepared by the conventional mixed oxides method [5,24] A Zeiss Supra 35VP field emission scanning electron microscope (FE-SEM) was used to obtain secondary electron, backscattered electron (BSE) and in-lens images of sample surfaces, fracture surfaces and polished cross-sections. Elemental composition information from BSE data were augmented with energy dispersive X-ray microanalysis (EDX) obtained with Oxford Instruments INCA system attached to the SEM.…”

“…Ag-electrodes fired in air at 800 o C were used [24]. An additional heat treatment was conducted in air at 800 o C for 1 hour with slow heating and slow cooling.…”

“…Indium oxide exhibits n-type conduction and is widely used for the preparation of transparent electrodes for optoelectronic devices [13][14][15] and gas-sensors [16][17][18]. However, it is well known that the addition of bismuth oxide (Bi 2 O 3 ) improves the sintering and promotes an increase in the nonlinearity coefficient in zinc oxide based and tin dioxide based varistor ceramics [19][20][21][22][23][24]. This suggests that bismuth oxide addition may also induce non-ohmic behavior in indium oxide ceramics.…”

Non-ohmic conduction in tin dioxide based ceramics with copper addition

“…However, the mechanism of non-ohmic conduction in SnO 2 varistor ceramics is still unclear. It was shown that addition of oxides with a low melting point (Bi 2 O 3 , V 2 O 5 , CuO) gives certain improvements in the density and electrical parameters of SnO 2 varistor ceramics [11][12][13][14][15]. Probably, addition of copper oxide to SnO 2 -CoO-Nb 2 O 5 -Cr 2 O 3 looks quite useful for the achievement of desired parameters of SnO 2 varistors [14,15].…”