THE DEVITRIFICATION BEHAVIOR OF INFRARED TRANSMITTING ALF3-[MGF2-CAF2-SRF2-BAF2]-YF3 GLASSES .1. DURING MELT COOLING

The AlF3-[MgF2-CaF2-SrF2-BaF2]-YF3 glass system has been optimised wit h the aim of minimising the extent of crystallisation which occurs on melt-cooling. Optical and scanning electron microscopy have been used to study the morphology and the distribution of small numbers of micro crystallites which are sometimes present in the optimised glasses. Sem i-quantitative energy dispersive spectrometry has indicated the compos ition of the microcrystallites. The stoichiometries of the crystalline phases have been proposed by comparison with the identity of crystall ine phases which grow when the glasses are reheated above the glass tr ansformation temperature (discussed in Part 2 ).