Structure of K₂O-B₂O₃ Glasses and Melts

抄録

The structures of potassium borate glasses and melts with 10 and 30 mol % K₂O have been studied by the use of pulsed neutron total scattering measurement. With an increase in K₂O content, the first peak of the experimental radial distribution function corresponding to nearest neighbor B-O correlation spread asymmetrically to the higher bond distance r side, and the coordination number of O atoms around a reference B atom, Nb–o, increased from 3.0 to 3.4 reflecting a structural change from BO₃ triangle units to BO₄ tetrahedral units. It can be concluded from the neutron results that some BO₃ units present are converted to BO₄ units on the addition of up to 30 mol % K₂O to the B₂O₃ melt in the same way as in K₂O-B₂O₃ glasses. XAFS studies of network modifying cations in alkali borate glasses have made an important contribution to our understanding of the structure of glass. The local structure in K₂O-B₂O₃ glasses has been determined in order to the elucidate the environment of network modifying K⁺ ions. The average coordination number, N_K-O, of oxygen around K⁺ cations and the mean distance, r_K-O, are found to be approximately 6 and 2.83∼2.86 Å, respectively. The XAFS results are in good agreement with X-ray diffraction and MD simulation results.