Fluorophosphate Glasses with High Terbium Content for Magneto-optical Applications

Fluorophosphate glasses are investigated following the composition law (1 - x)(70NaPO(3)- 30BaF(2)) - xTbF(3) with x = 3S, 40, 45, and 50 mol %. Bubble-free vitreous rods of 5 cm length and 4 mm in diameter are obtained without crystallization from 35 to 50 mol % of TbF3 by using the conventional melt-quenching process. The maximum content of Tb3+ ions successfully dissolved in these glasses corresponds to an ionic density of 8.88 X 10(21) ions cm(-3), which is the highest value ever reported in a fluorophosphate glass matrix, to our knowledge. Thermal, structural, and optical properties were characterized respectively by DSC, Raman spectroscopy, prism coupling technique, UV-visible-NIR, and Verdet constant measurement. The increase of the terbium content from 35 to 50 mol % in the glass results in an increase of its glass transition temperature (T-g) from 352 to 390 degrees C, a decrease of its thermal stability against crystallization (Delta T) from 153 to 73 degrees C, and an increase of both its refractive index and Verdet constant, respectively. A maximum value of Verdet constant of -78 rad T(-1)m(-1) at 650 nm is measured in the sample containing 50 mol % of TbF3.