Crystallization behaviour and properties of multicomponent strontium—Containing lithia calcia silicate glasses

摘要

The crystallization behaviour of lithia calcia silicate system containing MgO, SrO, and Al2O3 has been investigated using DTA, XRD and SEM. The coefficient of thermal expansion and Vicker’s microhardness of the obtained products were also evaluated. The main crystalline phases formed after different heat-treatments were lithium metasilicate, wollastonite, diopside, b-spodumene ss, pseudo-wollastonite, Sr_2SiO_4, Sr_2Mg(Si_2O_7) and m-(Ca,Sr)SiO_3. The wollastonite structure can accept considerable amount of strontium to form wollastonite strontium solid solution, while there is no solid solution of strontium in pseudo-wollastonite. The dilatometric thermal expansion of the glass–ceramics was determined and exhibited a wide range of a-values depending upon the type and relative proportions of the crystalline phases formed. The a-values of the studied glass–ceramic ranged between 47 and 105 × 10~(-7) K~(-1) in the 25–600 ℃ temperature range. The microhardness values of the crystallized samples were 539–730 kg/mm2. The compositions containing Al_2O_3 exhibited low thermal expansion and high microhardness values. The data obtained depend on the nature, concentration of crystalline phases formed and microstructure.