Effect of the melting conditions on the properties of glasses in the system PbO–ZnO–B2O3–SiO2

Abstract

Oxide system PbO-ZnO-B 2 O 3 -SiO 2 with the content of lead oxide of more than 45 mol.% is the basis of non-crystallizable low-melting glasses with softening temperature of lower than 450 0 Ñ. Lead-containing glasses are very aggressive, therefore they are melted in the platinum crucibles or ceramic crucibles which are resistant to the aggressive action of the lead glass melt. During the process of the melting of lead glasses in ceramic crucibles, the additives (Al 2 O 3 and SiO 2 ) are transferred from the crucible to the glass melt. An uncontrolled amount of these additives affects the properties of the glasses. The objective of this work was to establish the effect of the temperature-time conditions of melting on the physical and chemical properties of high-lead glasses prepared in both platinum crucibles and ceramic ones. The results of the study showed significant difference in properties of glasses synthesized in crucibles fabricated from different materials. Glass synthesized in the platinum crucible under various temperature-time conditions was characterized by stable physical and chemical characteristics and low softening temperature (~380 0°Ñ ) without any traces of crystallization under repeated heat treatment. The melting in the alumina crucible and quartz crucible under the same temperature-time conditions resulted in both a decrease in physical and chemical characteristics of low-melting glass and an increase in the glass softening temperature to 450-470 0 Ñ due to crystallization of glass during a heat treatment.

Tunable giant negative thermal expansion in Ti2O3-based polycrystalline materials

“…The major accomplishment of the present work in comparison with the previous studies 1, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] is the demonstration of the tunability of the temperature range where the NTE emerges. As shown in Figs.…”

“…In comparison with other NTE materials where the microstructural effects are important, the unique feature to the Ti 2 O 3 -based materials in this work is that NTE is observed in bulk poly-crystals in spite of the positive thermal expansion of a unit cell. This significant difference in the thermal expansion property between bulk and a crystallographic unit cell highlights the extremely important role of the microstructural effect in this material.The major accomplishment of the present work in comparison with the previous studies 1,[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] is the demonstration of the tunability of the temperature range where the NTE emerges. As shown in Figs.1(a)-1(c), pristine Ti 2 O 3 of sample (D) has the largest absolute value of NTE coefficient around approximately 473 K that corresponds to the metalinsulator transition temperature, indicating that the electronic state is strongly coupled with crystal lattice in this system.…”

“…Recently, giant NTE in a wide temperature range between room temperature and 600 K was reported for sintered Ti 2 O 3 polycrystalline sample, 20) but the mechanism of NTE is still unclear. Ti 2 O 3 crystallizes in a corundum structure, whose schematic structure is shown in the inset to Fig.…”

Effects of composition on the structure, thermal and some physical characteristics of Bi2O3-B2O3-ZnO-SiO2 glasses

“…Dilatometry is an essential technique for gaining insights into the thermal characteristics of glass, playing a pivotal role in evaluating its appropriateness for various uses [37]. The dilatometry curve (Fig.…”

“…This synergy allows for a broad compositional range and enhances the material's structural stability. The presence of zinc oxide further augments these properties, contributing to lower melting temperatures and improving the glass's chemical durability [8,9]. One of the most remarkable aspects of bismuth zinc borosilicate glasses is their application in photonic and optoelectronic devices [10].…”