Effect of SiO2/Al2O3 ratio on the structure and electrical properties of MgO-Al2O3-SiO2 glass-ceramics doped with TiO2

Glass-ceramics of the MgO-Al2O3-SiO2 (MAS) ternary system were successfully prepared through a melting method with borax, quartz sand, and chemical reagents as the main raw materials. The effects of SiO2/Al2O3 ratios on the structure and properties of glass-ceramics were systematically investigated by differential thermal analysis (DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), dielectric properties and electrical resistivity measurements. The results show that the average coefficient of thermal expansion (CTE) (30-800 degrees C) of all the samples increased with increasing of the SiO2/Al2O3 ratio, but the density of the glass-ceramics and the grain refinement decreased at the same time. The crystalline phase of all the samples was a prepared sapphirine phase when the SiO2/Al2O3 ratio was equal or greater than 1.78 and a second phase of enstatite precipitation. The electrical performance was the best when the SiO2/Al2O3 ratio was equal to 1.27, and its dielectric constant, dielectric loss, and electrical resistivity (room temperature) were 8.78 (1 MHz), 3.55 x 10(-3) (1 MHz), and 10.57 x 10(11) Omega m, respectively.