GLASS-CERAMICS BASED ON PHASES WITH NZP-TYPE STRUCTURE

Regions of glass formation are described that can be crystallized to g lass-ceramics consisting of one or two phases with NaZr2P3O12-type str ucture. One region is derived from NaGe2P3O12 through partial substitu tion of MgO for Na2O; it yields glass-ceramics with high thermal expan sion. By contrast, glass-ceramics with low or even negative thermal ex pansion are obtained from complex compositions of the type (Na, K)(1-x )(Mg, Ca, Sr)(x/2+y/2)AlyTi2-yP3O12 with y approximate to 1/2. With so dium contents above one mole per formula unit glass-ceramics can be ob tained that show ionic conductivity. However, the large conductivities of sintered ''Nasicons'' of analogous structure are not obtained, pro bably because of the structural complexity of the glass-ceramics.