Failure mechanisms in in-situ SEM micropillar compressions of pre-crystallized and crystallized zirconia-containing lithium silicate glass-ceramics

Abstract

Microscale microstructure-property relations for zirconia-containing lithium silicate glass-ceramics (ZLS) are critical for their applications as load-bearing restorations. This study investigated in-situ scanning electron microscopy (SEM) micropillar compression responses of pre-crystallized and crystallized ZLS materials with a flat diamond punch. Micromechanical properties (moduli, strength, ductility, resilience and toughness) of the two materials were determined. Pre-crystallized and crystallized ZLS materials showed distinct ductile-brittle failure mechanisms. Pre-crystallized ZLS containing weaker lithium metasilicate crystals and higher concentrated glass matrix revealed its ductile mode featured with bending and delamination, and side-splitting fractures originated from fragmentation and microcracking. Crystallized ZLS with stronger lithium disilicate crystals and lower concentrated glass matrix demonstrated bending and shear-band initiation, shear fracture from shear-band expansion and fragmentation. Further, crystallized ZLS yielded much higher moduli, strength, ductility, resilience and toughness than pre-crystallized ZLS. This study provides vital insights into the basic understanding of micromechanical behavior of ZLS materials for load-bearing applications.