DIELECTRIC-PROPERTIES OF CA-BASED COMPLEX PEROVSKITE AT MICROWAVE-FREQUENCIES

We have investigated microwave dielectric properties and crystal structures of Ca(B-1/2(3+) B-1/2(5+))O-3 (B:Al, Cr, Mn, Fe; B': Nb, Ta) and Ca(B1/32+B2/3'5+)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 (epsilon(r)), lower Q values, and larger negative temperature coefficients of resonant frequencies (tau(f)). Ca(Mg1/3Ta2/3)O-3 had the highest Q value (Qf=78000 GHz) in this investigation. All Ca(B1/2B2/3')O-3 had perovskite structures similar to C5LTiO(3) with a unit cell including four simple perovskite cells. Ca(B1/3B2/3')O-3 with a small B ion such as Ni had the same structure Ca(B1/2B1/2')O-3. Ca(B1/3B2/3')O-3, however, had perovskite structures with larger unit cells than CaTiO3 when B ions had larger ionic radii.