Low loss Sr1−xCaxLa4Ti5O17 microwave dielectric ceramics

Microwave dielectric ceramics in the Sr1−xCaxLa4Ti5O17 (0 ≤ x ≤ 1) composition series were prepared through a solid state mixed oxide route. All the compositions formed single phase ceramics within the detection limit of in-house X-ray diffraction when sintered in the temperature range 1450–1580 °C. Theoretical density and molar volume decreased due to the substitution of Ca2+ for Sr2+ which was associated with a decrease in the dielectric constant (ɛr) and temperature coefficient of resonant frequency (τf) but an increase in quality factor, Qfo. Optimum properties were achieved for Sr0.4Ca0.6La4Ti5O17 which exhibited, ɛr ∼ 53.7, Qfo ∼ 11,532 GHz and τf ∼ −1.4 ppm/°C.

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► New single phase highly dense (95%) microwave dielectric Sr1−xCaxLa4Ti5O17 (0 ≤ x ≤ 1) ceramics were designed and processed.
► Theoretical density and molar volume decreased due to the substitution of small Ca2+ for large Sr2+.
► As required for microwave dielectric applications, optimum properties (i.e. ɛr ∼ 53.7, Qfo ∼ 11,532 GHz and τf ∼ −1.4 ppm/°C) were achieved for Sr0.4Ca0.6La4Ti5O17 (x = 0.6).