Thermal properties of strontium–borate glasses and glass-ceramics containing bismuth and vanadium oxides measured with DSC method

Thermal properties of strontium–borate glasses and glass-ceramics containing bismuth and vanadium oxides was measured by DSC. The polycrystalline strontium–borate, SrB4O7 was synthesized via a solid state reaction route that involved heating stoichiometric mixtures of analytical grade SrCO3 and H3BO3 at 1073 K for 12 hours. Next, samples of a composition of x(2Bi2O3-V2O5)-(100-x)SrB4O7,where x=5 and 50 (in %mol) were prepared from reagent-grade Bi2O3, V2O5 and preprepared SrB4O7.While SBO glass samples (x = 0) were prepared from reagent-grade SrCO3 and H3BO3. Samples of glass were prepared by the conventional melt quenching technique. The melting was conducted in alumina crucibles at 1373 K for 2 hours. The melt was poured onto a preheated (573 K) brass plate and pressed by another plate to obtain flat circular disks of 1–2 mm thickness and 20–30 mm in diameter. Two types of samples were studied: as-quenched (SrB4O7, 5(2Bi2O3-V2O5)-95SrB4O7, 50(2Bi2O3-V2O5)-50SrB4O7) and heat-treated 50(2Bi2O3-V2O5)-50SrB4O7. Sample names were simplified to SBO, 5BiV-95SBO, as-quenched and partially crystallized 50BiV-50SBO. Partially crystallized 50BiV-50SBO samples were obtained by heat treating in air at a temperature of 693 K for 3 hours and then kept the samples in the furnace to cool to room temperature. The crystallization temperature was determined on the basis of the DSC spectrum. Differential scanning calorimetry (DSC) measurements were performed on powdered samples in a flow of nitrogen at 50 cm3 min−1 using a Netzsch STA 449F1 thermal analyzer. The heating rate was maintained at 15 K min−1 within a temperature range of 373–813 K.