Structure of Ta2O5 containing Phosphate Invert Glasses Prepared by Liquid Phase Method

Hayato Asano; Minori Takahashi; Akiko Obata; Makoto Sakurai; Fukue Nagata; Sungho Lee

doi:10.4028/p-KCC1Tq

Paper Titles

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Mechanical and Thermal Properties of Harmonic Structure Composites with Ti-Ni Alloy and Copper
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Structure of Ta₂O₅containing Phosphate Invert Glasses Prepared by Liquid Phase Method
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Investigation of Degradation Behavior of Adhesion between Sealing Resin and Copper by Aging Treatment
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Structure of Ta₂O₅containing Phosphate Invert Glasses Prepared by Liquid Phase Method

Abstract:

Tantalum-containing phosphate invert glasses were prepared using a liquid phase method under ambient conditions. In our previous study, the ion-releasing behavior (i.e. chemical durability) of phosphate glasses was controlled by the amount of intermediate oxides. In this work, Ta₂O₅ (intermediate oxide) was used to improve the chemical durability of the glasses. Ta-containing phosphate invert glasses were prepared and their structures were characterized. X-ray diffraction (XRD) patterns of the glasses exhibited broad halos, indicating an amorphous state. The amount of P₂O₅ in the glasses increased with increasing Ta₂O₅ content, while the amount of CaO decreased. The glasses prepared with a nominal P : Ta molar ratio of 2 : 1 showed a value of 1.87 : 1. Thus, almost all the Ta used in the synthesis was contained in the resulting glass. Raman spectra showed bands corresponding to short phosphate units such as ortho-and pyrophosphate, and the P-O-P peak was blue-shifted with increasing Ta₂O₅ content. The P-O-Ta bonds were formed with TaO₄ tetrahedra, as new peaks at 970 cm^-1 (P-O-Ta bonds) and 825 cm^-1 (observed in YTaO₄) were observed. The glasses containing higher amounts of Ta₂O₅ exhibited TaO₆-rich phases, as shown by the Raman band at 630 cm^-1 (Ta-O-Ta bonds) and broad XRD peaks at 2θ = 5 ~ 10°. Therefore, Ta in the phosphate invert glasses prepared by the liquid-phase method crosslinks phosphate units in the form of TaO₄ tetrahedra, and the excess Ta exists in the form of TaO₆ octahedra as a network modifier and/or Ta₂O₅-rich phase.