Capacitance-vs-voltage and frequency characteristics of SnO₂-Co₃O₄-Nb₂O₅-Cr₂O₃ ceramics

¹ Universidad Tecnológica de la Mixteca, Huajuapan de León, Oaxaca, C.P. 69000, Mexico
² Dniepropetrovsk National University, 13 Naukovyi St., 49050 Dniepropetrovsk, Ukraine

Corresponding author: alexbondua@yahoo.com

Received: 29 November 2008
Revised: 24 May 2009
Accepted: 9 September 2009
Published online: 30 October 2009

Abstract

Electrical properties of SnO₂-Co₃O₄-Nb₂O₅-Cr₂O₃ ceramics sintered at 1100−1400 °C were studied. Materials exhibit known varistor properties (superlinear and symmetric current-voltage characteristic) only if sintered at relatively high temperatures of 1300−1400 °C. In ceramics sintered at 1100−1200 °C, the current limiting effect (current is saturated and even decreased with voltage increase) and its transformation into the varistor effect were found. It was ascertained that the capacitance of samples is decreased with increasing frequency more sharply for ceramics sintered at 1100−1200 °C than at 1300−1400 °C. The low-frequency capacitance and ac conductance of ceramics sintered at 1100−1200 °C were increased and showed further strong decrease with electric field. The results of electrical measurements are discussed in terms of the barrier model.