Effects of P2O5 on crystallization, sinterability and microwave dielectric properties of MgO-Al2O3-SiO2-TiO2 glass-ceramics

Glass-ceramics of MgO-Al2O3-SiO2-TiO2-P2O5 were prepared by two-step heat-treatment at selected nucleation temperature and followed by crystallization temperatures. After the addition of 2.5 wt.% P2O5, the MgO-Al2O3-SiO2-TiO2-P2O5 glass-ceramics (abbreviated as P2.5) can be fully precipitated at ≤ 950 °C. The predominant phases in the glass-ceramics are found to be Mg2SiO4, Mg2Al4Si5O18, Ti4Si2P6O25 and SiO2 in the crystallization temperature range of 930- 970 °C. The results showed that P5 + could promote the phase separation of MgO-Al2O3-SiO2-TiO2 glass and that the glass was divided into two areas, such as Mg2SiO4 and the containing P5 + area at ≤ 950 °C. Furthermore, P5 + inhibited the presence of Mg2Al4Si5O18 when the heat treatment temperature was ≥ 950 °C. The 19.0MgO-23.0Al2O3-53.0SiO2-4.0TiO2-2.5P2O5 (wt.%) glass-ceramics (abbreviated as P2.5) exhibits the ultra-low dielectric constant εr ~ 3.9- 4.0 ± 0.1, a high quality factor Q × f ~ 13,785 ± 50 GHz at 13- 14 GHz and a near-zero temperature coefficient of resonant frequency τf ~ − 7.8 to − 6.4 ± 0.1 ppm/°C, suggesting that it will be a promising material in LTCC technologies. With the further increase of the P2O5 content up to 3.5 wt.%, the linear shrinkage, the density and dielectric properties inversely deteriorate.