SINTERING AND HUMIDITY-SENSITIVE BEHAVIOR OF THE ZNCR2O4-K2CRO4 CERAMIC SYSTEM

Solid state reaction at elevated temperatures and the sintering behavi our of zinc chromite formed by zinc oxide and chromite oxide were inve stigated. Crystalline structure, surface and fractured morphologies an d humidity-sensitivity characteristics of ZnCr2O4-K2CrO4-CuO were stud ied. The fired ceramic body, which proved to be mainly constructed fro m ZnCr2O4 spinel grains, was porous. The humidity characteristics of t he sensor showed that the resistance decreased as a logarithmic functi on with an increase in humidity. The resistance values obtained were a bout 6 x 10(9) Omega and 3 x 10(4) Omega at 25 and 93% relative humidi ty (RH), respectively. Based on a.c. impedance measurements, an equiva lent circuit associated with a network of resistors together with seri es capacitors has been suggested. It is assumed that such an equivalen t circuit model of the sensor under the moist conditions represents th e sensing mechanism as a diffusion process.