Abstract

Vitrification in the system of K₂O-BaO-B₂O₃-Al₂O₃-TiO₂ containing (mol%): K₂O (0 to 28), BaO (0 to 28), B₂O₃ (5 to 24), Al₂O₃ (7 to 25) and TiO₂ (33 to 60) was investigated by fusion at 1450°C for 2 h. The fields of vitrification were analyzed with different forms of diagrams. It is shown that stable glasses can be produced with batchs containing 62 to 75 mol% of glass-formers ([TiO₂]+[B₂O₃]+[Al₂O₃]) including (TiO₂) up to 48 mol% and (R₂O₃)>20 mol%. For those compositions with (TiO₂)=35 to 47 mol%, the molar ratio of (Al₂O₃) / (B₂O₃) can be varied in the range of 1 to 2.5. The structure of obtained glasses was characterized by scanning electron microscope (SEM) and infrared (IR); the investigated glasses contained one or two vitreous phases depending on their chemical composition. One-phase glasses can be obtained with compositions of (Al₂O₃) / (B₂O₃)≥1.75. The vitreous phase of one-phase glasses and the main glassy phase of two-phase glasses are formed by octahedra of TiO_6/2 and AlO_6/2 as well as (B₃O₆)^3- rings; the droplets of the second vitreous (borate) phase was formed by BO_3/2, TiO_4/2 and BO_4/2^-, AlO_4/2^- groups combined with Ba²⁺ and K⁺ cations.

Key words: Vitrification, borate, titanate, two-phase glasses.