Thick film capacitors with relaxor dielectrics

Thick film pastes destined for class II capacitors were developed, based on four relaxor ferroelectrics: Pb(Mg1/3Nb2/3)O3, Pb(Fe1/2Nb1/2)O3, Pb(Fe2/3W1/3)O3 and Pb(Zn1/3Nb2/3)O3, and two normal ferroelectrics: PbTiO3 and BaTiO3. The layers made of these pastes, without any addition of nonferroelectric fluxes, can be fired according to the conventional thick film procedure at 880–950 °C. The dielectric constant and dissipation factor of the layers were determined in the temperature range −55 to +125 °C and in the frequency range 10 Hz to 1 MHz. A model of the equivalent circuit was proposed on the basis of impedance spectroscopy studies. Resistivities of the thick films were measured in the temperature range 20–500 °C. Relaxor thick film capacitors manufactured in this work are characterised by: low firing temperature, high dielectric constant (200–4000), low changes in capacitance after dc bias ageing and good resistance to moisture.