Temperature‐Stable and Low‐Loss Dielectrics in the Ca(B′ _1/2 Ta _1/2 )O ₃ [B′=Lanthanides, Y, and In] System

Abstract

The Ca(B′ 1/2 Ta 1/2 )O 3 [B′=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, and In] double perovskite‐type ceramics have been prepared by the conventional solid‐state ceramic route. The phase purity and surface morphology of the sintered ceramics have been studied by X‐ray diffraction (XRD) and scanning electron microscopy methods. XRD study revealed intersubstitution between Ca and B′ ions. Ca(B′ 1/2 Ta 1/2 )O 3 ceramics have relative permittivity (ɛ r ) in the range 23–30, normalized quality factor ( Q u × f ) 20 600–59 200 GHz, and temperature coefficient of resonant frequency (τ f ) −6 to −35 ppm/°C. The dielectric properties of Ca(B′ 1/2 Ta 1/2 )O 3 ceramics have been tailored by the addition of positive τ f materials such as CaTiO 3 , TiO 2 , Ba(Y 1/2 Ta 1/2 )O 3 , and Ba(Yb 1/2 Ta 1/2 )O 3 , which form a solid solution or a mixture phase with the parent compound. The 0.7Ca(Y 1/2 Ta 1/2 )O 3 –0.3Ba(Y 1/2 Ta 1/2 )O 3 ceramic has ɛ r =27.5, Q u × f =41 900 GHz, and τ f =−1.2 ppm/°C, and the 0.6Ca(Yb 1/2 Ta 1/2 )O 3 –0.4Ba(Yb 1/2 Ta 1/2 )O 3 ceramic has ɛ r =27.7, Q u × f =48 000 GHz, and τ f =1.8 ppm/°C.