The influence of TiO2 and ZrO2 on microstructure and crystallization behavior of CRT glass

• TiO2 is an efficient nucleating agent in terms of CRT glass crystallization.
• TiO2 caused surface crystallization.
• Fresnoite glass ceramic is achievable due to TiO2 addition.

The crystallization process of silica–strontium–barium glass from Cathode Ray Tube (CRT) with various TiO2 and/or ZrO2 additions (0–15 wt.%) was studied by means of non-isothermal and isothermal analyses. The crystalline phase was determined by X-ray diffractometry. The micro-structures of the samples were studied by the SEM technique. Fresnoite glass ceramic samples were obtained by heat treating CRT glasses with 8 and 15 wt.% of TiO2 in a gradient oven. We found that the crystallization of fresnoite strongly depends on the kind, and amount of nucleating agents. The influence of TiO2 and ZrO2 content on the thermal properties of the glasses was analyzed. Their thermal characteristics such as the glass transition temperature Tg, the temperature of non-isothermal crystallization Tc, and the thermal stability parameter were determined by DTA/DSC. The linear expansion coefficients of the glasses as a function of temperature were measured. Based on the DTA results we found that TiO2 was effective in decreasing the crystallization temperature, whereas ZrO2 increased it. Only TiO2 in the CRT glass led to the surface crystallization of fresnoite.