Characterization of Neodymium Doped Calcium Tungstate Single Crystal by Raman, IR and Luminescence Spectroscopy

Abstract

The aim of the current work was to assess obtain a single crystal of calcium tungstate doped with neodymium - (CaWO4:Nd3+), and after that, the crystal was characterized with various spectroscopic methods. The single crystal was grown from the melt using the Czochralski method in air. By optimizing growth conditions, lt 001 gt -oriented CaWO4:Nd3+ crystalc up to 10 mm in diameter were grown. Number of dislocations in obtained crystal was 10(2) per cm(2). Micro hardness was measured with the Vickers pyramid. Anisotropy in lt 001 gt direction was not observed. Selected CaWO4:Nd3+ single crystal was cut into several tiles with the diamond saw. The plates were polished with a diamond paste. The crystal structure is confirmed by X-ray diffraction. The obtained crystal was studied by Raman and infrared spectroscopy. Seven Raman and six IR optical active modes predicted by group theory are observed. FTIR confirmed the occurrence of all the functional groups and bonds in this material. From the FTIR spectrum, a strong peak of 862 cm(-1) has been obtained due to the stretching vibration of WO42- in scheelite structure, and a weak but sharp band at 433 cm(-1) has been noticed due to the metal-oxygen (Ca-O) band. Estimated luminescence lifetime of F-4(5/2) - the I-4(9/2) transition is about 120 mu s; estimated luminescence lifetime of F-4(3/2) - the I-4(9/2) transition is about 140 mu s. All performed investigations show that the obtained CaWO4:Nd3+ single crystal has good optical quality, which was the goal of this work.