Structural and microwave dielectric properties of the (1−x) Li3NbO4−x Ca0.8Sr0.2TiO3 thermally stable ceramics

• (1−x) Li3NbO4−x Ca0.8Sr0.2TiO3 ceramics were prepared by mixed oxide route.
• The τf of Li3NbO4 was modified to near 0 ppm/°C by incorporating Ca0.8Sr0.2TiO3.
• The excellent dielectric properties of εr = 21.7, Q × f = 49,276 GHz were achieved.
• The optimized sintering temperature of the ceramics was 1075 °C.

The ceramic system of (1−x) Li3NbO4−x Ca0.8Sr0.2TiO3 prepared by solid reaction route has been found to possess excellent dielectric properties. Li3NbO4 was combined with Ca0.8Sr0.2TiO3 to obtain a two-phase ceramic system and to achieve a thermally stable material. As x value varied from 0.1 to 0.4, the temperature coefficient of resonate frequency values (τf) ranged from +119.1 ppm/°C to −30.7  ppm/°C. At x = 0.2, the 0.8 Li3NbO4–0.2 Ca0.8Sr0.2TiO3 ceramic sintered at 1075 °C for 4 h exhibited outstanding microwave dielectric properties with a relative dielectric constant (εr) ∼21.7, a quality factor (Q × f) value ∼49,276 GHz (at 6.1 GHz), and a τf ∼5.2 ppm/°C, which represented a promising candidate for microwave dielectric applications. Moreover, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were included in our work to help identify and analyze the phase assemblage and the microstructure of the sintered ceramics.