A new glass-free LTCC microwave ceramic – (1 − x) Li2.08TiO3 + xLiF

The structure and microstructure of the (1 − x) Li2.08TiO3 + xLiF (0.11 ≤ x ≤ 0.14) ceramics were studied by X-ray powder diffraction (XRD), thermal dilatometry and scanning electron microscopy (SEM). The microwave dielectric properties of the ceramics were studied with a network analyzer. All samples exhibited single monoclinic phase. The sintering temperature was successfully reduced to about 900 °C/2 h for the LiF-doped Li2.08TiO3 specimens. The dielectric permittivity slightly decreased, whereas the Q × f value changed little, with the increase in LiF dopant. The temperature coefficient of resonant of frequency (τf) value changed from positive to negative with increasing x, and a near zero value was obtained at x = 0.13 composition. Optimized microwave dielectric properties with ɛr = ∼22.8, Q × f = ∼63,000 GHz and τf = ∼1.0 ppm/°C for x = 0.13 composition sintered at 900 °C/2 h. The XRD and back scattering SEM analysis showed that the ceramic was compatible with Ag powders after sintering at 900 °C/2 h.