CHEMICAL-STABILITY OF SOME MANGANESE GLASS-CERAMICS

The chemical durability of some selected glass-ceramic materials based on the Li2O-(MnO,CaO)MgO-Al2O3-SiO2 glass composition has been determ ined using the HCl/powder test. The leachability of the glass ceramic was gradually increased by replacing MgO with MnO, while it was decrea sed by adding MnO instead of CaO. Calcium oxide had a retarding effect on the durability of the material when it was added instead of MgO an d/or MnO. The durability of the material was markedly improved by addi tion of Al2O3 in place of Li2O. The leaching values were found to be d ependent mainly on the proportion of the glass oxide constituents, i.e ., the MgO/MnO, CaO/MnO and Li2O/Al2O3 ratios in the nominal glass com positions. The results were correlated to different views concerning t he effect of various ions on the rate of interdiffusion between the gl ass-ceramic materials and the leaching solution, the types and proport ions of the crystalline phases developed, and the residual glass phase .