The ceramics, SrTiO₃ (ST) and 0.4, 0.8 atom% Ni doped SrTiO₃, were prepared by solid state reaction route. The average grain size of undoped and doped samples was measured and found to be 1.2, 1.9 and 3.7 𝜇m, respectively. The impedance measurements were conducted at 400–600°C to separate grain and grain boundary contributions. The grain and grain boundaries relaxation frequencies were shifted to higher frequency with temperature. Bulk resistance of doped and undoped ST ceramics was more or less the same. Single grain boundary resistance of doped sample was higher than that of undoped one, indicating that GB resistance increases with acceptor doping. Activation energies were calculated to confirm the same.

An efficient humidity indicating silica gel was prepared using rice husk ash as a raw material via sodium silicate extraction and acid neutralization method. Cobalt chloride was impregnated into the silica gel as a colour indicating material. A low concentration of cobalt chloride solution (0.0005 mol dm^-3) was used for the impregnation. The effect of pH of the impregnating solution on the colour development behaviour of the gel was investigated. The specific surface area of the gel was determined by Brunauer–Emmett–Teller method. The gel has been characterized using X-ray diffraction, scanning electron microscopy and visible spectroscopy. The moisture adsorption and desorption kinetics of the desiccant were evaluated using simultaneous thermogravimetry and differential scanning calorimetry.