Influence of glass-phase structure on the degradation of rare-earth (Y2O3, La2O3)-doped CaO–Al2O3–SiO2–B2O3 glass-ceramics in citric acid solution

Abstract

Liquid-phase sintering anorthite (LSA) glass-ceramics with degradation in citric-acid solution have been prepared from CaO–Al2O3–SiO2–B2O3 low-melting compositions. By means of the chemical corrosion of the glass phases, LSA glass-ceramics are effectively degraded in the citric acid solution. Then, the influence of B2O3 and rare-earth (RE) on the structures of glass phases, the degradation of LSA glass-ceramics in the citric-acid solutions, and the dielectric properties are investigated systematically. The results suggest that when the B2O3 molar ratio in the composition CaO–Al2O3–SiO2–B2O3 is 0.5, doping LSA glass-ceramics with RE can reduce the quantity of bridging oxygen and [BO4] units in the glass phase, as well as the degree of network connection of [AlO4] units in the glass network. Conversely, when the B2O3 molar ratio is decreased down to 0.3, doping RE into LSA glass-ceramics increases the quantity of bridging oxygen and [BO4] units for glass phase. This improvement in chemical stability effectively impedes the degradation of LSA glass-ceramics in citric-acid solutions. Concurrently, the degradation mechanism of LSA glass-ceramics in citric acid solution is analyzed and explained in terms of classical glass corrosion theory, while the microstructural characteristics of LSA glass-ceramics are utilized to investigate their dielectric properties. It indicates that the dielectric loss and dielectric constant of LSA glass-ceramics are significantly lowered as a result of the existence of the glass phase. Especially when the B2O3 molar ratio in the composition CaO–Al2O3–SiO2–B2O3 is 0.3, and the La2O3 doping percentage into LSA glass-ceramics is 0.5 wt%, the LSA glass-ceramics exhibit the lowest dielectric loss value of 3.13 × 10−3 and εr = 4.17. Developing the LSA glass-ceramic with degradation in organic acids can provide a new idea for the recycling and disposal of e-waste.