Three glass compositions, one corresponding to fl-Eucryptite, another corresponding to Lithium Metasilicate and the third corresponding to 1070°C eutectic on the lithium metasilicate-fl-eucryptite join in the composition triangle lithium metasilicate -fl-spodumene-fl-eucryptite of the system Li 2 0-Al 2 0 3 -Si0 2 were studied with respect to their crystallization behaviour. The phases crystallizing out after different heat treatment schedules and itsing different nucleating agents were identified by X-ray diffraction patterns. In all cases, the initial crystallization product was Eucryptite silica-0 form. However, in the case of 1070°C eutectic composition the development of lithium metasi/icate phase was also noticed after heat treating at 800°C for 5 hours.The first DT A peak due to crystallization was used to distinguish the effects of Zr0 2 , Ti0 2 and V 2 0 5 as nucleating agents. With 5% zirconia additions the first crystallization peak temperature was maximum while in the case of 5% V 2 0 5 additions it was minimum. There was, however, no change in the initial crystallization products with and without the nucleating agents.

No abstract

No abstract

A.P.) X-ray diffraction studies and densification measurements were carried out on three compositions, 75% Ti0 2 +25% Zr0 2 , 75% Ti0 2 +25% A/ 2 0 3 , and 100% Ti0 2 , designated as TZ, T A and T respectively, heated under oxidizing and reducing atmospheres between 1200"C and 1400°C. The densification was always higher and the formation of the new phases took place with greater ease when the specimens were fired under reducing conditions. This was possible due to the formation of anionic vacancies in the Ti0 2 structure, which would enhance diffusion.