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, (001)-oriented CaWO4:Nd3+ crystalс up to 10 mm in diameter were grown. Number of dislocations in obtained crystal was 102 per cm2. Micro hardness was measured with the Vickers pyramid. Anisotropy in (001) 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 wаs 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 4F5/2 - the 4I9/2 transition is about 120 µs; estimated luminescence lifetime of 4F3/2 - the 4I9/2 transition is about 140 µs. All performed investigations show that the obtained CaWO4:Nd3+ single crystal has good optical quality, which was the goal of this work.