. His results showed, that the maximum flexural strength
of glass–ceramics of 487 ± 40 MPa could be obtained by the Li+ ↔ K+
exchange at 500 °C for 5 h. Destruction and disappearance of lithium
di-silicate crystals caused by Li+ ↔ Na+ ion-exchange in NaNO3 molten
salt baths were observed.