Liquid phase effect of La2O3 and V2O5 on microwave dielectric properties of Mg2TiO4 ceramics

Abstract

Dielectric ceramics of Mg2TiO4 (MTO) were prepared by solid-state reaction method with 0.5–1.5 wt.% of La2O3 or V2O5 as sintering aid. The influences of La2O3 and V2O5 additives on the densification, microstructure and microwave dielectric properties of MTO ceramics were investigated. It is found that La2O3 and V2O5 additives lowered the sintering temperature of MTO ceramics to 1300 °C and 1250 °C respectively, whereas the pure MTO exhibits highest density at 1400 °C. The reduction in sintering temperature with these additives was attributed to the liquid phase effect. The average grain sizes of the MTO ceramics added with La2O3, and V2O5 found to decrease with an increase in wt%. The dielectric constant (er) was not significantly changed, while unloaded Q values were affected with these additives, and the values were in the range of 92,000–157,550 GHz and 98,000–168,000 GHz with the addition of La2O3 and V2O5, respectively. The dielectric properties are strongly dependent on the densification and the microstructure of the MTO ceramics. The decrease in Q×fo value at higher concentration of La2O3 and V2O5 addition was owing to inhomogeneous grain growth and the liquid phase which is segregated at the grain boundary. In comparison with pure MTO ceramics, La2O3 and V2O5 additives effectively improved the densification and dielectric properties with lowering of sintering temperature. The proposed loss mechanisms suggest that the oxygen vacancies and the average grain sizes are the influencing factors in the dielectric loss of MTO ceramics.