Yang C.-Y.Das S.Lu C.-H.2019-05-132019-05-13201500222313https://scholars.lib.ntu.edu.tw/handle/123456789/407360New phosphors Ca<inf>2</inf>Tb<inf>8-x</inf>Eu<inf>x</inf>(SiO<inf>4</inf>)<inf>6</inf>O<inf>2</inf> with color-tunability were synthesized in this work. The Rietveld refinement indicated that the prepared phosphors were crystallized to a hexagonal structure with space group P6<inf>3</inf>/m (no. 176). When Eu3+ ions were introduced into Ca<inf>2</inf>Tb<inf>8</inf>(SiO<inf>4</inf>)<inf>6</inf>O<inf>2</inf>, characteristic red-orange emissions of Eu3+ ions and the green emission of Tb3+ ions were obtained. Eu3+-doped phosphors emitted with enhanced intensity and had broader excitation spectra than the undoped Ca<inf>2</inf>Tb<inf>8</inf>(SiO<inf>4</inf>)<inf>6</inf>O<inf>2</inf> phosphors. As Eu3+ content increased, a decline in Tb3+ emission was observed owing to resonant energy transfer from the 5D<inf>3</inf> level of Tb3+ ions to the 5D<inf>0</inf> level of Eu3+ ions. Moreover, the transfer of energy from Tb3+ ions to Eu3+ ions proceeded via a dipole-dipole interaction, and the critical distance for this energy transfer was calculated to be 7.2 ?. The efficiency of energy transfer in Ca<inf>2</inf>Tb<inf>8-x</inf>Eu<inf>x</inf>(SiO<inf>4</inf>)<inf>6</inf>O<inf>2</inf> increased from 72% to 87% with an increase in the Eu3+ concentration, x, from 0.02 to 0.08. The emitted color of Ca<inf>2</inf>Tb<inf>8-x</inf>Eu<inf>x</inf>(SiO<inf>4</inf>)<inf>6</inf>O<inf>2</inf> was tuned from green to red via controlling the concentration of Eu3+ ions. Meanwhile, the optimum phosphor system Ca<inf>2</inf>Tb<inf>7.94</inf>Eu<inf>0.6</inf>(SiO<inf>4</inf>)<inf>6</inf>O<inf>2</inf> exhibited adequate thermal stability even at 200 ¢XC and the corresponding activation energy was calculated to be 0.027 eV. These results suggest that Ca<inf>2</inf>Tb<inf>8</inf>(SiO<inf>4</inf>)<inf>6</inf>O<inf>2</inf>:Eu3+ may be potential phosphors for the application in UV LEDs. ? 2015 Elsevier B.V. All rights reserved.Energy transferOxyapatitePhosphorsPhotoluminescenceSilicate[SDGs]SDG7journal article10.1016/j.jlumin.2015.08.0092-s2.0-84940388663https://www.scopus.com/inward/record.uri?eid=2-s2.0-84940388663&doi=10.1016%2fj.jlumin.2015.08.009&partnerID=40&md5=77cfab88c0cbde4d4ccd68110e1d1705