Chemical Strengthening of Glass‐Ceramics in the System Li2O‐Al2O3‐SiO2

Abstract
Fine‐grained glass‐ceramics containing a large proportion of β‐spodumene solid‐solution crystals were strengthened by immersion in molten sodium and potassium salt baths. An ion‐exchange reaction placed sodium or potassium ions in lithium ion sites in the β‐spodumene structure. The resultant “crowding” of the structure produced a surface compressive layer. In this system, strengths (modulus of rupture on abraded specimens) in excess of 100,000 psi were realized. In a similar manner, stuffed β‐quartz solid‐solution glass‐ceramics derived from the crystallization of Li2O‐Al2O3‐SiO2 glasses containing an appropriate amount of nucleating agent were strengthened by K+‐for‐Li+ exchange. Stable β‐quartz solid‐solution glass‐ceramics were strengthened by Na+‐for‐Li+ exchange, but no significant increase in strength was obtained in the metastable β‐quartz materials.

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