Yun Chuan Liu,Li Ying Zhang,Xiang Lei Yu,Wei Chao Li,Jun Peng Li,Guo You Gan
A high-temperature conductive silver slurry containing lead-free ZnO-B2O3-SiO2 glass for metallization of ceramic MgTiO3 substrate has been prepared. The ZnO-B2O3-SiO2 glass was obtained by high-temperature melting and cold extraction with a transition temperature (Tg) of 579 °C and thermal stability (∆T) of 105 °C as an inorganic bonding phase of high-temperature conductive silver paste. Then, silver paste with different glass powder content was sintered on ceramic MgTiO3 substrate between 730 °C and 930 °C in increments of 50 °C. Characterization of the prepared materials revealed that their resistivity increases with the increase in glass powder content and decreases with the increase in sintering temperature. Sintering temperature and glass content have significant effects on the resistivity and adhesion of the thick silver film. When the silver paste with a glass content of 1.1 wt% was sintered at 830 °C for 10 min, the resulting thick silver film had a low resistivity of 1.81 μΩ·cm (1.65 μΩ·cm for silver) and a good adhesive strength of 39.4 N mm−2. During the sintering process, the glass material melts and wets the silver powder, which promotes the sintering of the silver powder to form a dense network structure and improves the electrical conductivity of the silver film. In addition, the formation of ZnTiO3 by chemical reactions between the glass and the substrate was observed, which dramatically improved the bonding strength of the silver film. Therefore, lead-free silver paste containing ZnO-B2O3-SiO2 glass powder and MgTiO3 ceramics has broad development prospects in ceramic filters.
Herein, magnesium metatitanate (MgTiO3) ceramics were synthesised using recycled magnesia-hercynite (MH) bricks as the raw materials to achieve solid waste reusing of cement kiln refractories. The recycled MH materials were mixed with anatase TiO2 to investigate the effect of addition of doped B2O3 during the synthesis of MgTiO3 ceramics at 1400 °C. Phase compositions and microstructural studies were performed using x-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. In addition, energy-dispersive spectroscopy (EDS) was conducted and the dielectric properties of the samples were studied. Results show that the addition of B2O3 can promote sintering, improve shrinkage, promote densification, stabilise MgTiO3 lattice, and inhibit the formation of MgTiO3. In addition, the presence of appropriate amount of B2O3 can accelerate the material diffusion and result in grain growth through the formation of intercrystalline liquid phase. Results also suggest that an increase in dielectric constant results in a decrease in dielectric loss. It was concluded that 2 wt% was the optimum amount of B2O3 required to obtain the most favourable synthesis rate of MgTiO3 (98.2%). The samples exhibited a maximum density of 3.69 g·cm−3 and excellent microwave dielectric properties at εr = 18.28 and tanδ = 0.086.
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