Materials Transactions, Vol 56, No (2015) pp 1419 to 1421 Special Issue on Nanostructured Functional Materials and Their Applications © 2015 The Japan Institute of Metals and Materials Luminescence Properties of Ce/Tb/Sm Co-Doped Tellurite Glass for White Leds Application Tran Thi Hong1, Pham Duc Huyen Yen2, Vu Xuan Quang3 and Phan Tien Dung4,+ Da Nang University of Education, 459 Ton Duc Thang Road, Danang, Vietnam Vietnam National University, 144 Xuan Thuy Road, Hanoi, Vietnam Duy Tan University, K7/25 Quang Trung Road, Danang, Vietnam Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet Road, Hanoi, Vietnam In this work, the Ce/Tb/Sm doped glasses with the composition of TeO2-B2O3-ZnO-Na2O were synthesized by melt quenching process The photoluminescence properties of glasses doped with Ce3+, Tb3+ and Sm3+ single, doubly and triply doped TeO2-B2O3-ZnO-Na2O (TBZN) were studied by mean of emission and excitation spectra There was an overlap between Ce3+ emission and Tb3+, Sm3+ absorption in the wavelength range of 350500 nm Therefore, it was expected that an efficient energy transfer occurred from Ce3+ to Tb3+ and Ce3+ to Sm3+ ions When excited by ultraviolet wavelengths the co-doped glasses emit a combination of blue, green and red orange forming white light [doi:10.2320/matertrans.MA201509] (Received January 21, 2015; Accepted June 22, 2015; Published August 25, 2015) Keywords: Tellurite glass, rare earth, energy transfer, luminescence Introduction 48TeO2 : 30B2 O3 :10ZnO:10Na2 O:1CeO2 : 1Tb2 O3 The glasses doped with rare earth (RE) ions were studied extensively over the past few decades to produce luminescent 3D display devices, solid state lasers, optical detectors, optical fibers, fiber amplifiers, waveguides and white LED.14) Among RE ions, Ce3+ exhibits a high ultraviolet absorption coefficient due to the parity 4f-5d allowed electric-dipole transition.5,6) Due to the extensive overlap between Ce3+ emission and Tb3+ and Sm3+ absorption in near ultraviolet region, Ce3+ is always used as an efficient sensitizer for Tb3+ and Sm3+ to enhance the green emission of Tb3+ and orange-red emission of Sm3+.79) Recently, the white emissions were obtained by tuning the doped amount of Ce3+ and Tb3+ in various systems, such as in Sr2Al2GeO7,10) Ca2Al2SiO7,11) Ba2Gd2Si4O13.12) However, a limited number of works has been reported on white light emission from Tellurite glasses co-doped with Ce3+, Tb3+ and Sm3+ In this work, a series of Tellurite glasses doped with Ce3+, Tb3+ and Sm3+ (single, doubly and triply doped) were fabricated Luminescent properties as well as energy transfer processes from Ce3+ to Tb3+, Ce3+ to Sm3+ were investigated This research may open a new approach to fabrication of Tellurite glasses co-doped with Ce3+, Tb3+ and Sm3+ for white LED Experimental Procedure Glasses were prepared using the following molar compositions: 49TeO2 :30B2 O3 : 10ZnO:10Na2 O:1CeO2 ðabbreviated to GCeÞ 49TeO2 :30B2 O3 :10ZnO:10Na2 O:1Tb2 O3 ðGTbÞ 49TeO2 : 30B2 O3 :10ZnO:10Na2 O:1Sm2 O3 ðGSmÞ + Corresponding author, E-mail: dungpt63@gmail.com ðGCeTbÞ 48TeO2 : 30B2 O3 :10ZnO:10Na2 O:1CeO2 : 1Sm2 O3 ðGCeSmÞ 47TeO2 : 30B2 O3 :10ZnO:10Na2 O:1CeO2 :1Tb2 O3 :1Sm2 O3 ðGCeTbSmÞ All the above components were mixed and heated for hours in a platinum crucible at 1350°C in an electric furnace, RHF 14/8/301 by Carbolite-England The glasses were obtained by cooling the melt down to room temperature The resulting glasses were transparent colorless Then, the samples were cut and polished before any optical measurements Excitation and emission spectra of the samples were measured on a Horiba FluoroLog Spectrophotometer FL3-22 All the measurements were done at room temperature Results and Discussions Luminescence of RE3+ (RE = Ce, Eu, Sm) in single doped TBZN glass Ce ions in glasses can occur in a trivalent and tetravalent state, only the trivalent Ce3+ state with a single 4f electron (1s22s22p63s23p63d104s24p64d104f 15s25p6) has optical properties, while the tetravalent Ce4+ ion is non luminescent because the closed shell electronic structure (1s22s22p63s23p63d104s24p64d105s25p6) Therefore, all glasses in the present work can be treated as if only Ce ions at trivalent state exist Photoluminescence (PL) and excitation luminescence (PLE) of GCe, GTb, GSm sample are presented in Fig Excited by 350 nm (curve (a)), the PL of Ce3+ is a broad asymmetric blue band from 370 to 500 nm The PLE of Ce3+ (em = 418 nm) (curve (b)) consists of two strong bands centered at 350 nm and 310 nm The result shows that GCe sample could be a promising blue luminescence material for white LED application Exciting by 379 nm (curve (c)), the PL of Tb3+ consists of four intense bands centered at 488, 543, 586 and 621 nm, which are 3.1 1420 T T Hong, P D H Yen, V X Quang and P T Dung (a) (b) (d) (f) (c) (e) Fig CIE chromatic coordinates diagram for GCe, GTb and GSm sample Fig The PL and PLE of GCe, GTb and GSm (a) assigned to the transitions 5D4 ¼ 7F6,5,4,3 respectively.13,14) The 5D4 ¼ 7F5 (543 nm) transition is the most efficient The PLE of Tb3+ (curve (d)) consist of seven bands corresponding to 7F6 ¼ 5H7, 5L8, 5L9, 5G5, 5L10, 5G6 and 5D4 transitions at 319, 341, 352, 359, 369, 379 and 488 nm respectively.15,16) The result shows that GTb sample could be a promising yellowish green luminescence material for white LED application Under 402 nm excitation (curve (e)), the PL of Sm3+ consists of four intense bands centered at 562, 601, 645 and 710 nm, which can be assigned to the transitions G5/2 ¼ 6H5/2, 6H7/2, 6H9/2 and 6H11/2, respectively.17,18) Among the four observed bands, the 4G5/2 ¼ 6H7/2 transition is the most efficient The PLE of Sm3+ (curve (f )) were assigned to 6H5/2 ¼ 4D3/2, 6P7/2, 4F7/2, 6P5/2, 4G5/2 and I9/2,11/2,13/2 transitions at 362, 375, 402, 417, 439 and 475 nm.18) The result shows that GSm sample could be a promising reddish orange luminescence material for white LED application The CIE chromatic coordinates of single doped glasses TBZN:RE3+ (RE = Ce, Tb, Sm) are shown in Fig It is clear that GSm sample emits reddish orange light, GTb sample emits yellowish green light and GCe sample emits blue light Consequently, the white light emission could be achieved with simultaneously doped Sm3+, Tb3+, Ce3+ ions in the glass matrix TBZN Luminescence of RE3+ (RE = Ce, Tb, Sm) in doubly TBZN:RE3+ glass 3.2.1 Energy transfer between Ce3+ to Tb3+ and Ce3+ to Sm3+ ions Figure gives PL of GCeTb (curve (a)) and GCeSm (curve (b)) sample Exciting by 350 nm light, the emission spectra not only include blue emission from Ce3+ but also yellowish green emission from Tb3+ (in GCeTb sample) and reddish orange emission from Sm3+ (in GCeSm sample) These results indicate that the high intensity light output of Tb3+ and Sm3+ actually comes from the energy transfer 3.2 (b) Fig The PL of GCeTb (a) and GCeSm (b) (ex = 350 nm) process from Ce3+ to Tb3+ and Ce3+ to Sm3+, respectively In Fig 4(a), after Ce3+ absorbs ultraviolet light (260 380 nm), the electrons are pumped to 5d level, and then the non radiative electrons relax to the lowest sub-level of 5d level Finally they decay to 2F5/2 and 2F7/2 levels by radiative process, emitting the blue photons.10,1820) In Fig 4(a) the lowest excited 5d state of Ce3+ and 5D3 of Tb3+ are energetically close to each other, and the energy transfer from Ce3+ to Tb3+ can easily proceed After that, Tb3+ ions relax non radiatively to 5D4 levels emitting the yellowish green photons from 5D4 level In Fig 4(b) the lowest excited 5d state of Ce3+ and 4F9/2 of Sm3+ are energetically close to each other, and energy transfer from Ce3+ to Sm3+ can easily proceed After that the Sm3+ ions relax to 4G5/2 levels emitting reddish orange photons from 4G5/2 level White light emission from TBZN: Ce3+, Tb3+ and Sm3+ glass The PL of GCeTbSm sample under 350 nm excitation is shown in Fig It displays blue, yellowish green and reddish 3.3 Luminescence Properties of Ce/Tb/Sm Co-Doped Tellurite Glass for White Leds Application (a) 1421 (b) Fig CIE chromatic coordinates diagram of GCeTbSm sample Fig Energy-level diagram of Ce3+ and Tb3+ in GCeTb sample (a), Ce3+ and Sm3+ in GCeSm sample (b).10,1820) Acknowledgments The authors gratefully acknowledge financial support for this research from National Foundation for Science and Technology Development (NAFOSTED) of Vietnam REFERENCES Fig The PL of GCeTbSm sample (ex = 350 nm) orange bands coming from Ce3+, Tb3+ and Sm3+, respectively The combination generate a white light The CIE chromatic coordinates diagram of GCeTbSm sample under 350 nm excitation wavelengths is presented in Fig When excited by 350 nm, the GCeTbSm emits pure white light (point a, the CIE coordinates are x = 0,3750; y = 0,3245 and z = 0,3005) Conclusion A series of Ce3+, Tb3+ and Sm3+ single, doubly and triply doped in TBZN glasses were prepared and their optical properties were studied White 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7477 ... Properties of Ce/ Tb/ Sm Co- Doped Tellurite Glass for White Leds Application (a) 1421 (b) Fig CIE chromatic coordinates diagram of GCeTbSm sample Fig Energy-level diagram of Ce3 + and Tb3 + in GCeTb sample... matrix TBZN Luminescence of RE3+ (RE = Ce, Tb, Sm) in doubly TBZN:RE3+ glass 3.2.1 Energy transfer between Ce3 + to Tb3 + and Ce3 + to Sm3 + ions Figure gives PL of GCeTb (curve (a)) and GCeSm (curve... reddish orange luminescence material for white LED application The CIE chromatic coordinates of single doped glasses TBZN:RE3+ (RE = Ce, Tb, Sm) are shown in Fig It is clear that GSm sample emits