Dielectric behavior of Nb2O5-doped TiO2/epoxy thick films

TiO2/epoxy composite thick films containing the TiO2 powders doped with 4 and 10 vol% Nb2O5 heat treated under vacuum at 1050 and 1150 °C, were prepared by the screen printing and curing steps. The Nb2O5-doped TiO2 ceramic bulks demonstrated a higher effective dielectric constant at different densification environments, as compared with pure TiO2. The dielectric properties of the TiO2/epoxy thick films were improved if the heat-treated 4 vol% Nb2O5-doped TiO2 powder was incorporated instead of the un-doped and heat-treated 10 vol% Nb2O5-doped TiO2 powders. The disadvantage of the doped TiO2 having higher dielectric loss tangent could be minimized after its powder was properly treated and mixed with epoxy to form the TiO2/epoxy composite. A best result with the dielectric constant of 23 and the loss tangent of 0.046 was obtained for the 40 vol% TiO2/epoxy composite thick films, where the TiO2 powder was doped with 4 vol% Nb2O5 followed by calcination at 1000 °C in air and heat treatment at 1150 °C under vacuum.