Preparation, Crystallization and Mechanical Properties of Potassium Aluminosilicate Glass-ceramics

In this study,transparent K2O-Al2O3-SiO2(KAS) glass-ceramics with leucite as the main crystalline phase were prepared by melting-quench method and two-step heat treatment.The effects of SiO2/Al2O3ratio and heat treatment on crystallization and mechanical properties were studied.The crystallization kinetics and X-Ray Diffraction (XRD) results showed that SiO2/Al2O3ratio and heat treatment system had a direct impact on the crystallization behavior of potassium aluminosilicate glass-ceramics.When heat-treated at 680 ℃/2?h and 780 ℃/1?h,cracks generated on the surface of the sample with the addition of SiO2/Al2O3=4.8 (in mol) due to the huge difference in the coefficient of thermal expansion between glass matrix and surface.When the addition of SiO2/Al2O3(in mol) was 4,the sample with leucite as the main crystalline phase showed an excellent fracture toughness (1.46 MPa·m0.5) after the heat treatment of 680 ℃/2 h and 780 ℃/5 h.And there was a phase transformation from kaliophilite to leucite.The crystalline phases of the sample heat-treated at 680 ℃/8 h and 780 ℃/1 h were leucite and kaliophilite,which resulted in the visible light transmittance of 63% and the fracture toughness of 0.91 MPa·m0.5.Furthermore,after the heat treatment of 680 ℃/2?h and 780 ℃/5?h,the main crystalline phase of the sample with SiO2/Al2O3=3.2 (in mol) was still kaliophilite.Because leucite only grows on the surface of the sample and is hard to grow inward,it is hard to achieve the bulk crystallization of leucite in the sample with SiO2/Al2O3=3.2 (in mol).