Structure of K2O-B2O3 glasses and melts

The structures of potassium berate grasses and melts with 10 and 30 mol % K 2O have been studied by the use of pulsed neutron total scattering measurem ent. With an increase in K2O content, the first peak of the experimental ra dial distribution function corresponding to nearest neighbor B-O correlatio n spread asymmetrically to the higher bond distance r side, and the coordin ation 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 tetrah edral units. It can be concluded from the neutron results that some BO3 uni ts present are converted to BO4 units on the addition of up to 30 mel % K2O to the B2O3 melt in the same way as in K2O-B2O3 glasses. XAFS studies of n etwork modifying cations in alkali berate glasses have made an important co ntribution to our understanding of the structure of glass. The local struct ure in K2O-B2O3 glasses has been determined in order to the elucidate the e nvironment 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 t o be approximately 6 and 2.83 similar to 2.86 Angstrom, respectively. The X AFS results are in good agreement with X-ray diffraction and MD simulation results.