Pb-Based Dielectric Ceramics with a Small Temperature Coefficient of Dielectric Constant Firable in Low Oxygen Partial Pressures

Abstract

Dielectric properties of ceramics in the system Pb(Zn_1/3Nb_2/3)O₃-SrTiO₃ that contained Pb(Cu, Mn, Nb)O₃ were studied. Comparing with Pb(Zn_1/3Nb_2/3)O₃-SrTiO₃ binary system, temperature coefficient of dielectric constant decreased by incorporating Pb(Cu, Mn, Nb)O₃. This is probably because the atomic species forming perovskite increased then the phase transition of dielectrics got more diffused. Cu¹⁺ emphasized this effect than Cu²⁺ or another atoms. Furthermore, we found Cu or Mn promoted aging of dielectrics and changed the temperature dependence curve of dielectric constant to a double peak. The ceramics developed in the system Pb(Zn_1/3Nb_2/3)O₃-SrTiO₃-Pb{(Cu_1-xMn_x)_1/3Nb_2/3}O₃ had a high density and a high resistivity when fired in atmospheres of low oxygen partial pressure below 1000°C. The ceramics had a high dielectric constant (>4000), a small temperature coefficient of dielectric constant (within 10% between -25° and +85°C when standardizing at 20°C; meeting YB specification of JIS), and a smaller change rate of dielectric constant under DC bias voltage than conventional BaTiO₃. The ceramics obtained are useful as dielectrics for multilayer ceramic capacitors with copper internal electrodes.