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Structure of M2O–B2O3 (M: Na and K) glasses and melts by neutron diffraction

1999; Elsevier BV; Volume: 60; Issue: 8-9 Linguagem: Inglês

10.1016/s0022-3697(99)00143-2

1879-2553

Katsumi Handa, Yuji Kita, Shinji Kohara, Kentaro Suzuya, Takuro Fukunaga, M. Misawa, Tomoko Iida, Hirosi Iwasaki, Norimasa Umesaki,

X-ray Diffraction in Crystallography

The structures of alkali borate glasses, M2O–B2O3, and melts with 10 and 30 mol% M2O (M=Na and K) have been studied by pulsed-neutron total scattering measurements. With an increase of M2O content, the first peak of the experimental radial distribution function corresponding to the nearest neighbor B–O correlation spreads asymmetrically to the higher-r side, and the coordination number of O atoms around a reference B atom, NB–O, increases from 3.0 to 3.4∼3.5, reflecting a structural change from BO3 triangle units to BO4 tetrahedral units. It can be concluded from the neutron results that some of the BO3 units present are converted to BO4 units during the addition of up to 30 mol% M2O to the B2O3 and that they melt in a way similar to M2O–B2O3 glasses. XAFS studies in potassium borate glasses have made important contributions to our understanding of the network-modifying structure of glass. The local structure in K2O–B2O3 glasses has been determined in order to elucidate the environment of the network modifying K+ ions. The average coordination number, NK–O, of oxygen around K+ cations and the mean distance, rK–O, are found to be approximately 6 and 2.83–2.86 Å, respectively.