Effects of K doping and annealing on the grain size and giant dielectric constant of KxTi0.02Ni0.98-xO ceramics

Monovalent ion (MOI) doping effect on the grain size and giant dielectric constant (epsilon' similar to 10(4)) of lead free environment friendly NiO-based KxTi0.02Ni0.98-xO (KTNO, x = 0.04, 0.25, and 0.30) type ceramics have been investigated. Increasing K concentration (MOI) enhances the grain size along with the increase of epsilon' values. The dielectric constant of KTNO also increases with increase of the sintering time and temperature (within the range of our measurement) due to enhancement of crystalline size. The giant epsilon' value and the leakage current in KTNO show weak field dependent behavior. Estimated temperature coefficient of permittivity (TCP) of KTNO is very low (less than 6%). All these properties meet the requirements of the ceramics used in X7R EIA specification. High epsilon' in KTNO is attributed to the boundary layer mechanism.