| With the rapid development of modern microwave communication and radar technology, the microwave dielectric material which is applied to the X-band (8-12GHz) has a high value of the quality factor and whose resonant frequency temperature coefficient closes to zero. It has become the focus of attention of the Materials Research workers at home and abroad. The MgTiO3group ceramic is one of the high frequency thermal-stability ceramics which is widely used. The most important advantages of this group are that the raw materials are rich and cheap. But the sintering temperature of MgTiO3is as high as1400℃. What is more, the range of MgTiO3’s sintering temperature is very narrow and the dielectric properties in the microwave band still need to be improved. In this paper, doping and compounding MgTiO3to reduce the sintering temperature of MgTiO3and to improve its dielectric properties, which has important significance to the practical production applications.First of all, this paper took solid-phase sintering method to got a series of (Mg1-xZnx)TiO3ceramics (the following abbreviations for MZT) with different formulations and different sintering temperatures by doping Zn into MgTiO3. According to the results of the dielectric properties, density, XRD and SEM tests of the obtained ceramics, we can find out that with the increasing in the amount of doping Zn, both of bulk density and the radial contraction rate increased and the optimum sintering temperature decreased gradually. When x was0.4and0.5, the best sintering temperature decreased from1400℃癈to1200℃compared with MgTiO3. Also, with the increasing in the amount of doped Zn, dielectric constant increased, while the quality factor decreased and the temperature factor became more negative. Thus the sintering temperature of the Zn-doped ceramic reduced, while it did not improve the microwave dielectric properties of MgTiO3ceramic. When x was0.2, the sintering temperature of MZT at1250℃could get good dielectric properties: εr=\9, Qf=116000GHz, τf=-55ppm/℃.By taking the solid-phase sintering method,(Mg1-xZnx)TiO3(x=0.2) as the foundation was mainly studied to join high dielectric material Ba4Nd28/3Ti18O54·zBi2O3(BNT) to preparation microwave dielectric ceramic (1-m)(Mg0.8Zn0.2)Ti03·m{Ba6-3yNd8+2yTi18O54·zBi2O3}(m=0.1、0.2、0.3、0.4, z=012、0.15、0.18、0.2) to improve dielectric properties of MZT.According to the results, we could find out Bi3+could reduce the sintering temperature to make MZT and BNT composite in a lower sintering temperature(1200℃～1230℃) and to improve dielectric properties of MZT. When the m was constant value, as Bi3+incorporation increased, temperature coefficient of resonant frequency decreased but its value was still in the±10ppm/℃, and the quality factor reduced. When z was0.18, the sintering temperature of0.7(Mg0.8Zn0.2)Ti03·0.3{Ba6-3yNd8+2yTi18O54·zBi2O3} at1230℃could get good dielectric properties:εr=32.91, Qf=9877GHz, τf=1.1ppm/℃.When the doping amount of Bi3+was constant value, the changing of the value of m could improve dielectric properties. As the composite proportion m increased, the dielectric constant of the sample increased, temperature coefficient of resonant increased, and the quality factor closed to0gradually. When m was0.4, the sintering temperature of (1-m)(Mg0.8Zn0.2)TiO3·m{Ba6-3yNd8+2yTi18O54·0.15Bi2O3} at1200℃could get good dielectric properties:εr=40.77, Qf=5972GHz, τf=7.6ppm/℃. |
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