Qi Yuan,Yutong Meng,Sen Wang,Gaobin Liu,Qiyao Wang,Kuoming Song,He Zhao,Shuai Yan,Xin Li
The effects of different contents of B 2 O 3 -Bi 2 O 3 on the sintering temperature and dielectric properties of MgO-12%TiO 2 (w) ceramics were investigated. B 2 O 3 -Bi 2 O 3 addition effectively reduced the sintering temperature and improved the dielectric properties of ceramic samples; however, an excessive amount of B 2 O 3 -Bi 2 O 3 led to the deterioration of dielectric properties. This is because Bi 2 O 3 participated in the chemical reaction between MgO and TiO 2 and generated a high-dielectric-loss Bi 2 Ti 2 O 7 phase, resulting in an increased dielectric loss in the ceramic samples. In contrast, B 2 O 3 formed a liquid phase to fill the grain gaps and pores during sintering, improving the densities of the ceramic samples. An appropriate amount of B 2 O 3 -Bi 2 O 3 accelerated the reaction between MgO and TiO 2 and formed ultralow-dielectric-loss phases—MgTiO 3 and Mg 2 TiO 4 , and the dielectric losses of the ceramic samples decreased to an order of 10 −5 .
Fei Liu,Hanwei He,Lijin Cheng,Hao Li,Haizhou Bian,Shaojun Liu
The dielectric properties of microwave ceramics fabricated via additive manufacturing (AM) are generally lower than those of traditional dry-pressed ones. It is most likely attributed to the special laminated manufacturing method. In order to clarify this phenomenon, the vat photopolymerization technique was applied to fabricate crack-free Mg 2 TiO 4 ceramics by measuring manufacturing error of green bodies to determine the lower threshold value of exposure parameters. Under the condition of low power densities of 7.7–11 mW/cm 2 and short exposure time of 0.8 s, the vat-photopolymerized Mg 2 TiO 4 samples with manufacturing error of 12–31 µm were achieved. When the layer thickness increased from 20 to 50 µm, the number of laminated interfaces decreased by half, resulting in the obvious decrease in the number of pore defects along the laminated interface. Consequently, during the final stage of sintering, the number of pores needed to be excluded from the Mg 2 TiO 4 green bodies fabricated with the layer thickness of 40 and 50 µm was less than that fabricated with the layer thickness of 20 and 30 µm. Additionally, the grain growth of Mg 2 TiO 4 ceramics prepared with a larger layer thickness would proceed fully due to the weak inhibition from the less pores. Therefore, the relatively dense microstructure and fully grown grains contributed to the increase of quality factor values from 123,000 to 142,000 GHz as the layer thickness increased from 20 to 40 and 50 µm.
危险品化学品经营许可证（带存储）