Structural transformation and microwave dielectric properties of Li4Mg2SbO6F ceramics

A solid-state sintering process is used to fabricate Li4Mg2SbO6F oxyfluoride ceramics. The sintering behavior, phase structure as well as microwave dielectric performances of Li4Mg2SbO6F sintered bodies were studied. The phase transformation from cubic to orthorhombic occurred for Li4Mg2SbO6F ceramics sintered above 750 degrees C. The values of epsilon r, Q x f and tau f for Li4Mg2SbO6F ceramics were closely related to density, and configurational entropy caused by the phase transformation. The perfect microwave dielectric performances (epsilon r = 12.6, Q x f = 59,000 GHz (at 11.3 GHz), tau f =-37.0 ppm/K) could be acquired in Li4Mg2SbO6F ceramics following densification at 750 degrees C. A cylindrical dielectric resonator antenna was fabricated from the 0.15Li4Mg2SbO6F-0.85Li2SnO3 composite ceramics with close zero tau f, which showed good performances.