Relationship between structure and microwave dielectric properties of Li3Mg4Nb1-xTaxO8 ceramics

Abstract

Herein, the sintering behavior and dielectric properties of Ta5+-doped Li3Mg4NbO8 ceramics were investigated by solid-phase reactions in combination with first-principles calculations. In particular, Li3Mg4Nb0.96Ta0.04O8 illustrates the best dielectric properties after sintering at 1,175 °C with εr = 13.71 ± 0.20, Q × f = (132,112 ± 2,391) GHz (increased by 25%) and τf = (25.07 ± 1.36) × 10−6 °C−1. The non-intrinsic factors reflect that a small amount of Ta5+ doping produces a secondary phase, increased densification, and grain size, all of which optimize the dielectric properties. The dominant intrinsic factors indicate that the increase in bond ionicity, the greater polarization of Ta5+, and the blueshift of the Raman characteristic peak all lead to an increase in εr. The increase in lattice energy and the decrease in the damping behavior of the Nb/Ta-O bond vibrations lead to an increase in Q × f. The weakening of the Nb/TaO6 octahedral distortion leads to an optimization of τf. The modified Li3Mg4Nb0.96Ta0.04O8 ceramics have promising applications in microwave communications.

Keywords

• First-principles
• Li3Mg4NbO8, dielectric properties
• Lattice vibration