Effects of W6+ substitution on crystal structure and microwave dielectric properties of Li3Mg2NbO6 ceramics

Li3Mg2(Nb1-xWx)O-6(+x/2) (0 <= x <= 0.08) ceramics were synthesized by the solid-state reaction route. The effects of W6+ substitution on the phase composition, microstructure and microwave dielectric properties of Li3Mg2NbO6 ceramics were investigated systematically. The XRD results showed that all the samples formed a pure solid solution in the whole doping range. The SEM iamges and relative density revealed the dense structure of Li3Mg2(Nb1-xWx)O-6(+x/2) ceramics. The relationship between the crystal structure and dielectric properties of Li3Mg2(Nb1-xWx)O-6(+x/2) ceramics was researched through polarizability, average bond valence, and bond energy. The substitution of W6+ for Nb5+ in Li3Mg2(Nb1-xWx)O-6(+x/2) ceramics significantly promoted the Q x f values. In addition, the increase of W6+ content improved the thermal stability of the Li3Mg2(Nb1-xWx)O-6(+x/2) ceramics. The Li3Mg2(Nb0.94W0.06)O-6.(03) ceramics sintered at 1175 degrees C for 6h possessed excellent properties: epsilon(r) similar to 15.82, Q x f similar to 124,187 GHz, tau(f) similar to -18.28 ppm/degrees C.