Phase, microstructure and microwave dielectric properties of Zr-doped SrLa4Ti5?xZrxO17

The effect of Zr⁺⁴ substitution for Ti⁺⁴ on the phase, microstructure and microwave dielectric properties of compositions in the SrLa₄Ti_5−xZr_xO₁₇ (0 ≤ x ≤ 0.1) series was investigated. All the compositions formed single phase ceramics within the detection limit of in-house X-ray diffractometer when sintered in the temperature range 1,450–1,580 °C for 4 h in air. The substitution of Zr⁺⁴ for Ti⁺⁴ enabled processing of highly dense ceramics with a decrease in temperature coefficient of resonant frequency (τ_f) from ~117 to 70 ppm/°C, dielectric constant (ε_r) from 60.8 to 57.3, with no significant effect on the quality factor. In the present study, optimum properties i.e. ε_r ~ 57.3, τ_f ~ 70 ppm/°C and quality factor (Q _u  × f _o ) ~ 9,841 GHz, were achieved for SrLa₄Ti_4.9Zr_0.1O₁₇. The trend of the results demonstrates that further studies with increased Zr⁺⁴ content are required to achieve ultra low loss SrLa₄Ti_5−xZr_xO₁₇ ceramics.