Dielectric Properties of Ca-Based Complex Perovskite at Microwave Frequencies

Abstract

We have investigated microwave dielectric properties and crystal structures of Ca(B 3+ 1/2 B 1/2 ′5+ )O 3 (B: Al, Cr, Mn, Fe; B ′ : Nb, Ta) and Ca(B 2+ 1/3 B 2/3 ′5+ )O 3 (B: Mg, Ca, Co, Ni, Cu, Zn; B ′ : Nb, Ta) perovskite ceramics. Compared with well-known Ba-based perovskite dielectrics, the Ca-based complex perovskite dielectrics had lower relative permittivities ( ε r ), lower Q values, and larger negative temperature coefficients of resonant frequencies (τ f ). Ca(Mg 1/3 Ta 2/3 )O 3 had the highest Q value ( Q f =78000 GHz) in this investigation. All Ca(B 1/2 B 1/2 ′ )O 3 had perovskite structures similar to CaTiO 3 with a unit cell including four simple perovskite cells. Ca(B 1/3 B 2/3 ′ )O 3 with a small B ion such as Ni had the same structure Ca(B 1/2 B 1/2 ′ )O 3 . Ca(B 1/3 B 2/3 ′ )O 3 , however, had perovskite structures with larger unit cells than CaTiO 3 when B ions had larger ionic radii.