Structural evolution, sintering behavior and microwave dielectric properties of (1−x)Li2TiO3 + xLiF ceramics

Structural evolution, sintering behavior, and microwave dielectric properties of (1−x)Li2TiO3 + xLiF (0.05 ≤ x ≤ 0.70) ceramics have been studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Raman spectra, thermal dilatometry and microwave resonant measurement at the frequency of about 7–11 GHz. The results show that Li2TiO3 can form limited solid solution with LiF (x ≤ 0.4) and LiF second phase appeared when x30.5. The structure of the solid solution transformed from ordered monoclinic phase (β-Li2TiO3 (ss)) to disordered cubic rock salt (α-Li2TiO3 (ss)) when x30.15. The presence of short range ordering was confirmed for the cubic phase. The sinterability was considerably improved by doping with LiF. Densified ceramics with about 95–98% theoretical density could be obtained for the doped compositions after sintering at 900–1150 °C/2 h. An optimized microwave dielectric properties with εr of ~23.6, Q × f of ~108,000 GHz and τf of ~4.2 ppm/°C could be obtained for the x = 0.1 composition after sintering at 1100 °C/2 h.