Mat. Res. Bull., Vol. 24, pp. 163-168, 1989. Printed in the USA. 0025-5408/89 $3.00 + .00 Copyright (c) 1989 Pergamon Press plc. PREPARATION OF HIGH PURITY LANTHANUM COMPOUNDS FOR USE IN FLUORIDE OPTICAL FIBERS K. J. Ewing, L. Buckner, J. Jaganathan R. Ginther and I.D. Aggarwal Naval Research Laboratory Optical Sciences Division Code 6505 Washington, DC 20375 (Received September 21, 1988; Refereed) ABSTRACT The preparation of ultra-pure lanthanum nitrate by co- precipitation is described. Preparation of high purity lanthanum carbonate from the pure nitrate is also described. Hydrofluorinationof pure lanthanum carbonate produces high purity lanthanum fluoride used in the preparation of heavy metal fluoride glasses. MATERIALS INDEX: fluoride, carbonate, nitrate, lanthanum Introduction Heavy metal fluoride glass fibers composed of zirconium, barium, lanthanum, aluminum, and sodium fluorides(ZBLAN) have been Rroposed for ultra-long repeaterless fiber communication links. 1,2,3,4 Theoretically the intrinsic loss of such fibers will be 0.01 dB/Km at 2.55 uM [5] an order of magnitude better than silica fibers. However, the transition elements iron, cobalt, nickel, and copper, as well as the rare earth neodymium absorb in the vicinity of 2.55um causing much higher losses than theoretically predlcted. 6,7 In order to attain the theoretical minimum loss of 0.01 dB/Km, transition element and rare earth impurity concentrations in the individual metal fluorides or the glass must meet those listed in Table I. The impurity concentrations shown in Table I are calculated using the equation: [imp], ng/g - L/(wt.%~ (1) where: [imp] impurity concentration, ng/g L - 0.0004dB/Km/component/impurity ion wt. % weight percent of individual component in glass a absorbtivity of individual impurity ion in glass 7 [(dB/Km)/(ng/g)] 163