Refractive Index and Abbe's Number of Glass of Lanthanum Borate System

Abstract

On the basis of previous studies of the glass formation range of borate systems and the relation of composition, refractive index and Abbe's number of borate glass, optical region of lanthanum borate glasses on nD-ν diagram and its possible limit of high refractive and low dispersive side were investigated. These lanthanum borate glasses contained oxides of Ti, Zr, Th, Nb, Ta, W, Ba, and Al, and their glass formation range of 4- or 5-component systems were studied. Then the refractive index and Abbe's number of lanthanum borate glasses were measured and from their data and following equations the component factors were calculated.nD=1.445+Σiai+Σibixi2ν=(nD-1)/(0.521+Σikixi)nDai, bi, ki and xi are component factors and molar fraction of MinOm.As a result, it has been proved that caluculated values show good agreement with experimental values. On the basis of this result, then, optical region was researched on nD-νdiagram. And the resulted limiting line of high refractive and low dispersive side passes every point of nD=1.70, ν=55; nD=1.80, ν=50; nD=1.90, ν=40 and nD=2.00, ν=35.