Synthesis and characterization of Ag doped CaW04 powder phosphors for optical blue emission

This paper reports on the synthesis of Ca( 1-x )WO 4 : Ag x (0 ≤ x ≤ 0.05 mol %) powder phosphors by a hydrothermal method and followed by calcinations. The effect of Ag-content on photoluminescence (PL) spectra of CaWO 4 was investigated. The phase nature of the synthesized powder phosphors have been examined from X-ray diffractometry. Thermal decomposition behaviors of the dried CaWO 4 powder phosphors have been studied from TG/DTA profiles and thus noticed that there exists a polymorphic transition at 800 °C. Based on the PL results, the dopant Ag content in the phosphors has been optimized to be 0.001 mol %, displaying a prominent blue emission from the phosphor. From the FT-IR spectrum, a strong peak at 845 cm -1 has been obtained due to the stretching vibration of WO 4 2- in scheelite structure, and a weak but sharp band at 445 cm -1 has also been noticed due to the metal, oxygen (Ca-O) band. Scanning Electron Microscopic (SEM) studies reveal that the synthesized CaWO 4 and Ag-doped CaWO 4 particles are in plate shape in the range from 400 nm to 1 micron. From SEM images, it has been noted that the agglomeration of synthesized powder phosphors has been increased with the change in Ag content, owing to the density variation.