Low loss dielectrics in the Ca(B ' Nb-1/2(1/2))O-3 [B ' = lanthanides, Y] system

Abstract

The Ca(B'Nb-1/2(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 (epsilon r) in the range 23-32, normalized Q-factor (Q(u) x f) 11 000-38 000 GHz and temperature coefficient of resonant frequency (tau f) -43-5.2 ppm/degrees C. The microwave dielectric properties of Ca(B'Nb-1/2(1/2))O-3 ceramics are found to depend on the ionic radii of B'-site elements and tolerance factor (t). The substitution of Ba2+ and Sr2+ for Ca2+ resulted a phase transition in Ca(B'Nb-1/2(1/2))O-3 ceramics. The (Ca0.05Ba0.95) (Y1/2Nb1/2)O-3 has tau f close to zero (1.2 ppm/degrees C) with epsilon r =35 and Q(u) x f = 48 500 GHz and is proposed as a useful material for base station applications. Dielectric properties of the Ca(B'Nb-1/2(1/2))O-3 ceramics were tailored by the addition of TiO2 and CaTiO3