Synthesis and characterization of Ag doped CaWO4 powder phosphors for optical blue emission

This paper reports on the synthesis of Ca((1-x))WO4: 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 CaWO4 was investigated. The phase nature of the synthesized powder phosphors have been examined from X-ray diffractometry. Thermal decomposition behaviors of the dried CaWO4 powder phosphors have been studied from TG/DTA profiles and thus noticed that there exists a polymorphic transition at 800 degrees 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 WO42- 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 CaWO4 and Ag-doped CaWO4 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.