Microwave dielectric properties of Mg4Nb2O9 ceramics with excess Mg(OH)2 produced by a reaction-sintering process

Microwave dielectric ceramics of Mg4Nb2O9 with various excess Mg(OH)(2) were synthesized by the reaction-sintering process method. The effects of excess Mg(OH)(2) on the sintering behavior, phase composition, microstructures and microwave dielectric properties were investigated. XRD patterns show that Mg(OH)(2) as raw materials is more beneficial to obtain the pure Mg4Nb2O9 phase than that of MgO. The microwave dielectric properties of Mg4Nb2O9 ceramics strongly depended on the sintering temperature, microstructures and secondary phase MgO. With 0.03 M excess Mg(OH)(2) addition, the Mg4Nb2O9/MgO composite ceramics sintered at 1400 degrees C have excellent microwave dielectric properties of epsilon(r)=12.6, Q x f=196,700 GHz and tau(f)=-47 ppm/degrees C. @ 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.