The Infrared Spectra of Rubidium Borates of Varying Composition

Abstract

Abstract : The infrared transmission spectra of a series of rubidium borates consisting of varying proportions of rubidium oxide and boron oxide have been studied in the 2.5 to 15.5-micron range. The rubidium oxide concentration varied from 4.2 to 50 mole percent. Frequency assignments were made for molecular groups in these rubidium borates. The results can be interpreted to indicate that an increasing proportion of trigonally coordinated boron atoms in the borate glass network structure became tetrahedrally coordinated as the Rb20 content was increased up to 33 mole percent. This was accompanied by a simultaneous increase in the concentration of terminal B-O groups. Glasses containing Rb2O in excess of 33 mole percent tended to devitrify as boron reverted to trigonal coordination. At 50 mole percent, the rubidium metaborate structure resembled that of sodium metaborate. Selected metal oxides, introduced into glasses of high Rb2O content, entered into complex formation with B-O groups to reconstitute the network structure of the glass.