Pressureless sintered lithium disilicate glass-ceramics: Influence of particle size and crystallization state

The pressureless sintering process is essential to densify near net shaped parts with good shape fidelity. In this work, the impact of the particle size distribution and crystallization state on the processing and properties of final sintered multicomponent lithium disilicate (SiO2-Li2O-K2O-P2O5-Al2O3-ZnO) was evaluated. Higher densification was achieved by pressureless sintering at lower temperatures for samples prepared with fine glass-based powders (825 °C; ≈96%) rather than coarse crystallized powders (975 °C; 92.9%). However, samples based on fine powders presented a microstructure characterized by low aspect ratio crystals, while those based on coarse powders presented needle-like crystals with high aspect ratio. Best mechanical properties were found in samples prepared with coarse glass powders (relative density≈ 95.1%; Vickers Hardness≈ 5.2 GPa; indentation fracture toughness≈ 2 MPam0.5; flexural strength≈ 317 MPa) sintered at 875 °C-1h. These results can provide valuable orientations for the post-processing of lithium disilicate glass-ceramics prepared by additive manufacturing techniques.