玻璃吸收光谱InfraredIR.ppt

500cm-1 pentaborate, tetraborate and diborate groups. 550 cm-1 isolated diborate groups. 660cm-1 pentaborate groups. 806cm-1 Boroxol ring. 770cm-1 BO4 unit. 950 cm-1 pentaborate and tetraborate groups. The shift of the 950cm-1 to a lower value (925cm-1) is attributed to the linking of pentaborate and tetraborate groups to the orthoborate type of structure. 840 and 1210 cm-1 symmetric stretching of the B-O-B bridges and to the stretching of the terminal B-O- bonds, respectively, in B2O5-anions. (pyroborate) 1300~1500cm-1 stretching of B-O- bonds. Raman spectra of xLi2O-(1-x)B2O3 glasses (J. Phys. Chem. Solids, 54 (1993) 621) X=0.1 X=0.15 X=0.2 X=0.25 X=0.3 X=0.35 X=0.4 X=0.5 * Boroxol unit; B2O3 (b) pentaborate unit;Li2O-5B2O3 (c) triborate unit; Li2O-3B2O3 (d) orthoborate unit; 3Li2O-B2O3 (e) metaborate unit; Li2O-B2O3 (f) pyroborate unit; 2Li2O-B2O3 (g) diborate unit; Li2O-2B2O3 (h) loose BO4. Solid circlea represent boron atoms and open circles oxygen atom. An open circle with a negative sign indicates a non-bridging oxygen. The schematic representation of different borate arrangements. * Low frequency Raman spectra in xLi2O-(1-x)B2O3 glasses The low frequency part of the Raman spectra of glasses is dominated by the so-called “boson” peak. It represents the extent of short-range ordering where a phonon can propagate with no damping. the SCR can be estimated simply from the relation 2s = vtpc /w where vt is the transverse acoustic waves, w is the peak position of the boson peak. The short-range ordering in lithium borate glasses as shown in figure below does not exceed the dimension of one six-membered ring (8 ). The formation of BO4 units which results from the addition of Li2O to B2O3 frustrates the preferential ordering of the BO3 triangles and therefore reduces the SCR to 4.2 (at x = 0.50) in the lithium borate glasses. 135 cm-1 band in lithium borate glasses may be attributed to the torsion modes of BO3 and BO4 units. * 玻璃吸收光譜 Infrared (IR) 為電磁波的一頻譜區