Investigation on microwave dielectric properties and microstructures of (1−x) LaAlO3-xCa0.2Sr0.8TiO3 ceramics

• A novel (1−x) LaAlO3-xCa0.2Sr0.8TiO3 microwave ceramics were investigated.
• The ceramics formed a solid solution confirmed by XRD and EDS.
• When x increases, the ceramics Q × f·τf decrease, while εr increased nonlinearly.
• 0.5LaAlO3–0.5Ca0.2Sr0.8TiO3εr ∼ 32.7, Q × f ∼ 33400 GHz, τf ∼ −2.5 ppm/°C.

The structural, microstructural and microwave dielectric properties of (1−x) LaAlO3-xCa0.2Sr0.8TiO3 ceramics prepared by the conventional solid state ceramic route have been investigated. The formation of solid solutions (1−x) LaAlO3-xCa0.2Sr0.8TiO3 was confirmed by the X-ray diffraction patterns and the EDS analysis. The lattice parameter, average grain size and dielectric constant (εr) increase with increasing amount of Ca0.2Sr0.8TiO3 whereas the quality factor (Q × f) decreases. The increasing temperature coefficient of resonant frequency (τf) caused by the decreasing tolerance factor with x ranging from 0.3 to 0.7. The τf can be tuned near zero at x = 0.5. Specimen with the composition of 0.5LaAlO3–0.5Ca0.2Sr0.8TiO3 possesses an excellent combination of microwave dielectric properties: εr ∼ 32.7, Q × f ∼ 33400 GHz, τf ∼ −2.5 ppm/°C.