New temperature stable (Nd1-xLax)1.02Nb0.988O4 microwave dielectric ceramics

(Nd1-xLax)(1.02)Nb0.988O4 ceramics with enhanced microwave dielectric properties were prepared via conventional solid-state reaction route. The effects of La3+ ions substitution for Nd3+ ions on the microwave dielectric properties of the NdNbO4 ceramics were investigated. Microscopic analysis showed that the specimens presented single NdNbO4 phase in the range of x=0.0-0.05, with a further increase of the amount of La3+ ions, LaNb5O14 phase appeared in the system. The variation tendency of dielectric constant was in accordance with the relative density. The Qxf value and tau(f). value were correlated to packing fraction and bond strength, respectively. A near zero tau(f) value can be obtained by carefully adjusting the substitution of La3+ content. At 1250 degrees C, the (Nd1-xLax)(1.02)Nb0.988O4 ceramics with x=0.05 possesses excellent microwave dielectric properties: epsilon(r)=2132, Qxf=45,600 GHz (at 7.512 GHz) and tau(f)=0 ppm/degrees C. (C) 2015 Elsevier B.V. All rights reserved.