Effect of Zn2+ doping Li2Mg3Ti0.91(Al0.5Nb0.5)0.09O6 on structures and microwave dielectric properties

Li 2 Mg 3 Ti 0.91 (Al 0.5 Nb 0.5 ) 0.09 O 6 -based microwave dielectric ceramics with high dielectric constant, quality-factor and temperature stability were prepared by conventional solid-state reaction method. Influence of Zn 2+ dopant on structures and microwave dielectric properties of Li 2 Mg 3 Ti 0.91 (Al 0.5 Nb 0.5 ) 0.09 O 6 ceramics were investigated by X-ray diffraction and Raman spectroscopy. The X-ray diffraction results showed that no new phase was produced with the zinc addition before y = 0.08, above that some ZnTiO 3 peaks with very low intensity appear in the low-angle region of the diffraction pattern. The results of the scanning electronic microscope confirmed that Zn 2+ doping helped grains growth, reduced grain boundaries and made grains distribution uniform. All of these improvements have led to great dielectric constant ( ε r ), superior quality factor ( Q × f ) and outstanding temperature coefficient of resonance frequency ( τ f ). A microwave dielectric ceramic based on Li 2 Mg 3 Ti 0.91 (Al 0.5 Nb 0.5 ) 0.09 O 6 with optimum Zn 2+ content sintered at optimum temperature, exhibiting better comprehensive dielectric properties: ε r = 14.51, Q × f = 158,120 GHz, τ f = −13.0 ppm/°C.