Dielectric Properties of (PbCa)(MeNb)O₃ at Microwave Frequencies

Abstract

We have investigated the dielectric properties up to microwave frequencies of ceramics represented as (Pb 1- x Ca x )-(Me m Nb 1- m )O 3 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)(Mg 1/3 Nb 2/3 )O 3 , (PbCa)(Ni 1/3 Nb 2/3 )O 3 and (PbCa)-(Fe 1/2 Nb 1/2 )O 3 with perovskite structure. These dielectric constants and the Q values for a near-zero temperature coefficient are ε r =73 with Q =1330, ε r =59 with Q =1700 and ε 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.