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(Zn1/3Nb2/3)O3-SrTiO3 that contained Pb(Cu, Mn, Nb)O3 were studied. Comparing with Pb(Zn1/3Nb2/3)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(Zn1/3Nb2/3)O3-SrTiO3-Pb{(Cu1-xMnx)1/3Nb2/3}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.