Low Loss Dielectrics in the Ca(B′ _1/2 Nb _1/2 )O ₃ [B′=Lanthanides, Y] System

Abstract

The Ca(B′ 1/2 Nb 1/2 )O 3 [B′=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, and In] complex perovskites have been prepared by conventional solid‐state ceramic route. The structure and microstructure of the ceramics have been characterized by X‐ray diffraction and scanning electron microscopy methods. The ceramics have dielectric constant (ɛ r ) in the range 23–32, normalized Q ‐factor ( Q u × f ) 11 000–38 000 GHz and temperature coefficient of resonant frequency (τ f ) −43–5.2 ppm/°C. The microwave dielectric properties of Ca(B′ 1/2 Nb 1/2 )O 3 ceramics are found to depend on the ionic radii of B′‐site elements and tolerance factor ( t ). The substitution of Ba 2+ and Sr 2+ for Ca 2+ resulted a phase transition in Ca(B′ 1/2 Nb 1/2 )O 3 ceramics. The (Ca 0.05 Ba 0.95 ) (Y 1/2 Nb 1/2 )O 3 has τ f close to zero (1.2 ppm/°C) with ɛ r =35 and Q u × f =48 500 GHz and is proposed as a useful material for base station applications. Dielectric properties of the Ca(B′ 1/2 Nb 1/2 )O 3 ceramics were tailored by the addition of TiO 2 and CaTiO 3 .