Structural Evolution and Coordination Behavior of Ta⁵⁺ in Binary Li₂O-Ta₂O₅ Melts: In Situ High-Temperature Raman and...

This study aims to elucidate the structural evolution of Ta⁵⁺ in the binary Li₂O-Ta₂O₅ melts. The melt structure was characterized by using in situ high-temperature Raman spectroscopy. Combined with constructed Ta-O cluster models and quantum chemistry ab initio calculations to simulate Raman spectra, quantitative analysis of different coordination structures in melts was achieved by the deconvolution of the experimental spectra. Furthermore, the influence of Li₂O content on melt microstructure was systematically investigated via high-energy X-ray scattering and empirical potential structure refinement simulations. Results reveal the coexistence of three coordination species ([TaO₄], [TaO₅], and [TaO₆]) in melts. Their distribution exhibits a regular evolution with increasing Li₂O content: the proportions of five- and six-coordinated Ta-O species gradually decrease, while the four-coordinated Ta-O species increases significantly. This work provides crucial theoretical support for establishing correlations between species with various coordination structures and physical properties in binary Li₂O-Ta₂O₅ melts, as well as for optimizing interfacial dynamics through controlled crystal growth parameters.