Dielectric Properties of Ca-Based Complex Perovskite at Microwave Frequencies

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Abstract
We have investigated microwave dielectric properties and crystal structures of Ca(B3+ 1/2B1/2 ′5+)O3 (B: Al, Cr, Mn, Fe; B′: Nb, Ta) and Ca(B2+ 1/3B2/3 ′5+)O3 (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(Mg1/3Ta2/3)O3 had the highest Q value (Q f=78000 GHz) in this investigation. All Ca(B1/2B1/2 ′)O3 had perovskite structures similar to CaTiO3 with a unit cell including four simple perovskite cells. Ca(B1/3B2/3 ′)O3 with a small B ion such as Ni had the same structure Ca(B1/2B1/2 ′)O3. Ca(B1/3B2/3 ′)O3, however, had perovskite structures with larger unit cells than CaTiO3 when B ions had larger ionic radii.