Abstract
A new type of glass-ceramic containing calcium-mica crystals, in which numerous zirconia nano-particles are dispersed, exhibits high strength (-500 MPa in bending) and good machinability. This nano-composite structure is formed by controlling the growth rates of the precipitated crystals, i.e., zirconia and mica. The precipitation of mica crystals was controlled by the amount of fluorine in the mother glasses. A glass, in which the mica crystals were precipitated by heat treatment at low temperature, was converted into a micro-composite type of glass-ceramic containing zirconia crystals with -100 nm in size. This glass-ceramic was machinable, and its bending strength and fracture toughness were 310 MPa and 3.4 MPa⋅m0.5, respectively. The formation of tetragonal zirconia in sub-micronmeter size will lead to increase in the fracture toughness. These results imply that the tough glass-ceramics with "micro/nano"-composite structure can be prepared by controlling the crystallization.
