Study of the TiO2−H2O−B2O3 Ternary System at 7.7 GPa and High Temperatures

• Published in: Chemistry of materials 2002-01, Vol.14 (1), p.130-134
• Main Authors: Conceição, Rommulo V, Soares, Sérgio R. S, Balzaretti, Naira M, Pereira, Altair S, Costa, Tania M. H, Gallas, Márcia R, da Jornada, João A. H
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm0103242

The TiO2−H2O−B2O3 ternary system was studied at high pressure (7.7 GPa) and high temperatures, and a phase diagram is proposed. Depending on the initial stoichiometric conditions, Raman spectral analysis identified rutile, TiO2-II, H3BO3, HBO2, and B2O3 as the crystalline stable phases, and an amorphous phase constituted by B, Ti, and O. The eutectic point of this system was identified to be at around 400 °C. Two piercing points were located at around 600 and 1100 °C, identified by the stabilization of HBO2 rather than H3BO3, and B2O3 rather than HBO2, respectively. This study shows that TiB2 sintering at high pressure can be compromised by the presence of oxide-bearing phases that decrease the eutectic point of the system. This phenomenon can produce a liquid that works as a medium for transporting material, producing grain growth, which compromises the boride properties.