DIELECTRIC-PROPERTIES OF (PBCA)(MENB)O3 AT MICROWAVE-FREQUENCIES

We have investigated the dielectric properties up to microwave frequencies of ceramics represented as (Pb1-xCax)-(MemNb1-m)O3 where Me is selected from Li, Na, Mg, Zn, Ni, Co, Fe, Y, Yb, Al and Cr. High Q values and small temperature coefficients of resonant frequency were obtained in (PbCa)(Mg1/3Nb2/3)O3, (PbCa)(Ni1/3Nb2/3)03 and (PbCa)-(Fe1/2Nb1/2)O3 with perovskite structure. These dielectric constants and the Q values for a near-zero temperature coefficient are epsilon(r) = 73 with Q = 1330, epsilon(r) = 59 with Q = 1700 and epsilon(r) = 91 with Q = 1650, respectively. The other ceramics with smaller amounts of perovskite phase had degraded characteristics, i.e., low Q values or large temperature coefficients. In lead- and calcium-based perovskite, it seems that the high dielectric constant occurs due to Pb content in A-sites and smaller average ion radius in B-sites.