Solid state synthesis of europium and praseodymium doped silicate oxyapatites phosphor

• Main Author: Nyang, Tze Wei
• Other Authors: Dong Zhili
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Materials
• Online Access: http://hdl.handle.net/10356/39390
• Institution: Nanyang Technological University

Silicate oxyapatites with (1) varying concentration of Europium (Eu) and Praseodymium (Pr) (Formula: Sr2Y8 – x Kx (SiO4)6O2, where K= Eu, Pr) and (2) varying divalent cation (Formula: A2Y7.9 K0.1 (SiO4)6O2, where A = Strontium (Sr), Calcium (Ca), Magnesium (Mg) and K= Eu, Pr) were prepared using solid state synthesis method. Stoichiometric amounts of powder materials were being mixed and dissolved in ethanol before being ball-milled for 12 hours. The powder samples were then sintered in furnace at 1400oC for 6 hours. The diffractograms of sintered powders were obtained using Shimadzu X-ray Diffractometer (XRD), using CuKα as source with scan range from 10o to 80o. Analysis of all diffractograms showed that all powders are in apatite crystal structure, with small amount of yttrium oxide (Y2O3). The presence of Y2O3 might be due to the reason that ball-milling was not performed adequately. Also, one cycle of mixing, ball-milling and sintering will not be sufficient to convert all starting materials into desired powder samples even though mixing and ball-milling operation were performed adequately. Diffractograms also shows that the unit cell of samples does not change significantly with increasing concentration of Eu and Pr, but lattice constant “a” increases slightly with increasing ionic radii of Mg, Ca and Sr. The photoluminescence properties of silicates oxyapatites was then determined using Shimadzu Spectrofluorophotometer RF-5301. All samples doped with Eu show strong red emission at 613nm. They can be excited at wavelength 275nm and 393nm, which corresponds to charge transfer state (CTS) band and Eu3+ intra-4f transitions respectively. For excitation at 275nm, peak intensity increases with increasing Eu concentration initially but decreases after it reaches optimum Eu concentration, which is in agreement with concentration quenching effect. For excitation at 393nm, the peak intensity increases with increasing Eu concentration. The effect of different divalent cation on peak intensity is insignificant. There is no light emission at all for all Pr-doped samples because majority of Pr ions are in Pr4+ state, which does not give photoluminescence properties.