Microwave Characteristics of A(B ³⁺ _1/2 B ⁵⁺ _1/2 )O ₃ Ceramics (A = Ba, Ca, Sr; B ³⁺ = La, Nd, Sm, Yb; B ⁵⁺ = Nb, Ta)

Abstract

Dielectric properties of A(B 3+ 1/2 B 5+ 1/2 )O 3 (A = Ba, Ca, Sr; B 3+ = La, Nd, Sm, Yb; B 5+ = Nb, Ta) ceramics have been investigated at microwave frequencies. Sr(B 3+ 1/2 B 5+ 1/2 )O 3 and Ca(B 3+ 1/2 B 5+ 1/2 )O 3 ceramics have relative dielectric constants (ε r ) above 20 and negative temperature coefficients of resonant frequency (T f ). In the group of Ba(B 3+ 1/2 B 5+ 1/2 )O 3 ceramics, T f changes from + 118 ppm/° to nearly zero according to the kinds of B‐site ions. Among the ceramics investigated, Sr(Sm 1/2 Ta 1/2 )O 3 ceramics have the highest Q values at microwave frequencies. For Sr(Sm 1/2 Ta 1/2 )O 3 ceramics Q = 7000, ε r = 27.7, and T f =−62.5 ppm/° at 8.5 GHz. The microstructure of Sr(Sm 1/2 Ta 1/2 )O 3 ceramics is composed of a matrix of the ternary compound (Sr‐Sm‐Ta‐O system) and secondary phase grains of the binary compound (Sm‐Ta‐O system).