Low Dielectric Constant Of Fused Quartz Ceramics

From the beginning of 1950s, the fused silica ceramics was a major manufacturing missile radome materials because of its excellent chemical and mechanical properties. Fused silica ceramics has low dielectric constant, it caused the attention of researchers'. For microwave dielectric materials, it with low dielectric constant can be applied to produce high-frequency microwave devices. In recent years, with the rapid development of mobile communication technology, the microwave communication business has also been greatly improved. As the carrier of microwave devices, the dielectric materials have a direct impact on devices'performance. The researchers used different ways to research the microwave dielectric materials which applied for different frequency. Fabricating a certain frequency range and low loss substrate material has very important significance on the development of devices.In this paper, the main object of study is about the fused silica ceramics which can be included in low dielectric constant materials. At first, the phase transformation of quartz crystal is the basic research. It is also the theoretical basis for the rule to set out sintering technology with solid-phase synthesis for fused silica ceramics. And taked material for a wide range of analysis. Then adulterated different impurities in the material to modify the performance. In order to make the performance of fused silica ceramics can be further optimized, this paper also researched the impact of the dopant.For the non-doped fused silica, the main technology is solid-phase synthesis method and take rapid heating, short-term heat preservation sintering process to sinter. The performance of the samples obtained with internally generated types of crystalline phase. The phase transformation influenced by the sintering temperature. Carried out by a number of sintering temperature experiments, when the sample sintered at 1150℃for 1h, its bulk densityρ=2.165g/cm3, its realtive density is 98.2% at the low sintering temperature,εr=3.40, dielectric loss tgδ= 6.86×10-4, Qf = 12000.Having identified the basic fused silica ceramic sintering process then this paper taked the study of the doped materials. At first, conducting a systematic research on doped H3BO3. H3BO3 can suppress the crystal phase in the sintering process. After determining the amount of H3BO3 doping, respectively, were co-doped MgO, Al2O3 and MnO in a series of studies. The result found, doping MgO could improve the material sintering density, doping Al2O3 could improve the material dielectric properties and increase the dielectric constant, doping MnO could reduces the dielectric loss. The samples were also taking CaO-Al2O3 doping research, these two substances in the material doped make the promotion of crystal growth, enhance the density of the sample. Comprehensive series of test results in various doping, doping 3wt%H3BO3+0.5wt% MnO samples sintered at 1220℃for 1h, which had the best performance, its bulk densityρ=2.25g/cm3,εr=3.96, dielectric loss tgδ=10.5×10-4, Qf =11000.