HYPERSENSITIVITY AND NEPHELAUXETIC EFFECT OF ND(III) IN SODIUM BORATE GLASSES

An investigation of the optical absorption spectra of 1 mol% Nd2O3 in sodium borate glasses with Na2O contents varying from 7.5 to 40 mol% is presented. The glasses were obtained by quenching melts consisting of Na2CO3, H3BO3, and Nd2O3 (900 to 1100 degrees C, 1.5-2 h) between steel plates. The optical absorption spectra were recorded at 300 and 20 K. Special emphasis is laid on the positions, half-widths, intensities and shapes of the I-4(9/2) --> P-2(1/2) and the hypersensitive I-4(9/2) --> (4)G(5/2), (2)G(7/2) transitions. The observed property versus composition variations are discussed in terms of the covalency of the neodymium-oxygen bond and of changes induced into the crystalline field around-the Nd3+ ions by structural changes of the glass matrix. The shape of the hypersensitive transition is used for comparison with existing models on the rare earth environment in oxide glasses.