Structure stability, bond characteristics and microwave dielectric properties of co-substituted NdNbO4 ceramics.

Abstract Structure-property relationship of co-substituted (Mg2+ 1/4 Mo6+ 3/4)5+, (Al3+ 1/3 Mo6+ 2/3)5+, (Si4+ 1/2 Mo6+ 1/2)5+, (Zr4+ 1/2 Mo6+ 1/2)5+ for Nb5+ in NdNbO 4 ceramics was investigated systematically. The remarkable differences in dielectric properties of each composition originated from their bond characteristics and structure stability. The elongated/compressed bonds have an effect on the cell volume and polarization. And the average bond covalency of Nb-O bond was responsible for the development of permittivity. Q×f values and the total lattice energy went up to maximum when (Si 0.5 Mo 0.5) occupied Nb-site. Variations of lattice energy together with Nb-O bond energy suggest that a more stable structure was obtained through co-substitution. The optimal microwave dielectric properties is: ε r = 18.97, Q×f = 49466 GHz, τ f = 7.34 ppm/°C for NdNb 0.97 (Si 0.5 Mo 0.5) 0.03 O 4 , sintered at 1250 °C. [ABSTRACT FROM AUTHOR]