Thermal expansion of some borate and silicate compounds in glassy and crystalline states

Thermal expansion of some glassy, partly crystalline and crystalline compounds was investigated. For example, for lithium disilicate it was shown from data of the thermal expansion coefficient (TEC) at temperatures higher than T _g, that the crystalline phase content can be calculated. In PbO-ZnO-B₂O₃ system the TEC values of two compounds in glassy and crystalline states are given. By measurements of barium diborate samples crystallised from the glass powder, a large dilatometric hysteresis in the cooling-heating curves was detected. This phenomenon is tentatively attributed to crystal phase changes.