CALORIMETRIC AND DIFFERENTIAL THERMAL-ANALYSIS STUDIES OF GLASSES IN THE TERNARY-SYSTEMS ZRF4-BAF2-AF (A=NA,LI)

Ternary fluorozirconate glasses in the systems ZrF4-BaF2-NaF and ZrF4B aF2-LiF have been prepared in sealed Pt ampoules and examined by diffe rential scanning calorimetry and differential thermal analysis. The gl ass compositions were constrained along compositional joins with const ant Ba/Na(Li)=1 or constant F/Zr=5(5.5). The glass transition temperat ure T-g was observed to decrease with increasing alkali content and wi th decreasing size of the alkali ions, between Na+ and Li+. The depend ence of T-g on the F/Zr ratio shows a minimum in T-g for a F/Zr ratio between 5 and 5.5. The most stable glasses are found in this compositi on region. The observed solidus and liquidus temperatures of the sampl es in the ZrF4-BaF2-LiF system were compared to phase diagram data pre viously published for the ZrF4-BaF2-NaF system. Significantly higher l iquidus and solidus temperatures are observed for the ZrF4-BaF2-LiF sa mples. The glass forming regions of the two systems are located in dee p eutectics in the phase diagrams.