Microwave Dielectric Properties of Ca ₄ La ₂ Ti _{5− x} ( Mg _1/3 Nb _2/3 ) _x O ₁₇ Ceramics

Abstract

Using the solid‐state ceramic route, Ca 4 La 2 Ti 5− x ( Mg 1/3 Nb 2/3 ) x O 17 (0 ≤ x ≤ 4) ceramics were prepared, and the phase purity, microstructure, and microwave dielectric properties were investigated. The XRD results suggest the formation of solid solutions for all studied compositions (0 ≤ x ≤ 4) and the unit cell volume increases linearly with x . The SEM results also show no evidence of secondary phase and doping ( Mg 1/3 Nb 2/3 ) at Ti site promotes the grain growth. The ε r of sintered ceramics decreases from 71.86 to 35.23, the Q × f value increases from 15 070 to 21 277 GHz and the τ f value varies from 125.2 to −16.7 ppm/°C with x increasing from 0 to 4. A near‐zero τ f (~1.62 ppm/°C) is achieved at x = 3 with ε r ~ 40.45 and Q × f ~ 19 123 GHz.