| With the rapid development of microwave communication technology,medium-dielectric constant microwave dielectric ceramics with low loss are key materials for resonators in mobile base stations and satellite communications.The Zr O2-Ti O2 binary ceramic system has a high dielectric constant and Q×f value,but its resonant frequency temperature coefficient is a large positive value.Meanwhile,Mg Nb2O6 is also a potential microwave dielectric material with wide attention??r=23,Q×f=104000 GHz,?f=-61 ppm/??.Thus,?1-x?Zr Ti2O6–x Mg Nb2O6 ceramic system was investigated to obtain the ceramic with near zero?f value.The variations in the phase compositions,the structures and the microwave dielectric properties were studied with x value.With increasing x value,the ceramics with two phases became the one with a single phase of?-Pb O2 structure,and then to columbite structure when x value increased further.The dielectric constant and the temperature coefficient decreased.At the x level of 0.25-0.3,ceramics with near zero?f values could be obtained with low quality factor.Based on the investigations,the effect of Mn CO3 on the phase structure,the microstructure and the microwave dielectric properties of 0.73 Zr Ti2O6–0.27Mg Nb2O6 ceramic was studied.The Mn doping could improve the quality factor efficiently.At the level of Mn CO3=0.7 wt%,the ceramic had good microwave dielectric properties:?r=44.0?Q×f=31700 GHz?at 6.5 GHz?and?f=-4.8 ppm/?.Further studies on the Al2O3-doped 0.73Zr Ti2O6–0.27Mg Nb2O6 ceramic were carried out.The conductive active energy,the band gap and the microwave dielectric properties were investigated with Al2O3 additives.The effect of oxygen vacancies from the ceramic sintered in air could be suppressed by Al 2O3 in0.73Zr Ti2O6–0.27Mg Nb2O6,which contributed the improvement of the conductivity,the band gap and the quality factor.When the Al2O3 additive was1.0 wt%,the ceramic exhibited good microwave dielectric properties:?r=43.8?Q×f=33900 GHz?at 6.6 GHz? and ?f=3.1 ppm/?. |
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