Preparation and characterization of new dielectric ceramics Ba₅LnTi₂Nb₃O₁₈ (Ln = La, Nd)

Abstract

Two new A₆B₅O₁₈ type cation-deficient perovskites Ba₅LnTi₂Nb₃O₁₈ (Ln = La, Nd) were prepared by the conventional solid-state reaction route. The phase and structure of the ceramics were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Both compounds crystallize in the trigonal system. Ba₅LaTi₂Nb₃O₁₈ has a dielectric constant of 56.6, a high quality factors (Q _u × f > 16,700 at 4.3331 GHz), and a relatively large temperature coefficient of resonant frequency (τ _f ) + 142 ppm°C⁻¹ at room temperature; Ba₅NdTi₂Nb₃O₁₈ has a higher dielectric constant of 47.3 with high quality factors Q _u × f > 15,000 at 4.6830 GHz, and τ _f + 128 ppm°C⁻¹.