Up-Conversion Luminescence of Er 3+ /Pr 3+ /Yb 3+ Co-doped LaNbO 4 Phosphors
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https://doi.org/10.1007/s11664-020-08329-x 2020 The Minerals, Metals & Materials Society
Up-Conversion Luminescence of Er3+/Pr3+/Yb3+ Co-doped LaNbO4 Phosphors ˜ O P.C. DO NASCIMENTO ,1,5,7 FELIPE F. DO CARMO,2,5 JOA MARCELLO X. FAC ¸ ANHA,3,5 JUSCELINO C. SALES,4,5 DANIEL X. GOUVEIA,1,5 HUMBERTO D. DE ANDRADE,6 ´ NIOR,6 and ANTONIO S.B. SOMBRA5,6 IDALMIR S. QUEIROZ JU 1.—Instituto Federal de Educac¸a˜o, Cieˆncia e Tecnologia do Ceara´, PPGET, Fortaleza, Ceara´, Brazil. 2.—Departamento de Quı´mica Orgaˆnica e Inorgaˆnica, Centro de Cieˆncias, Universidade Federal do Ceara´ (UFC), Fortaleza, Brazil. 3.—Faculdade de Educac¸a˜o de Crateu´s (FAEC), Universidade Estadual do Ceara´ (UECE), Fortaleza, Ceara´, Brazil. 4.—Centro de Cieˆncias Exatas e Tecnologia, Universidade Estadual Vale do Acarau´ (UVA), Campus da Cidao, Sobral, CE CEP 62.040-370, Brazil. 5.—Departamento de Fı´sica, Laborato´rio de Telecomunicac¸o˜es e Cieˆncias dos Materiais e Engenharia (LOCEM), Universidade Federal do Ceara´ (UFC), Fortaleza, CE, Brazil. 6.—Universidade Federal da Regia˜o do Semia´rido (UFERSA), Mossoro´, RN CEP 59625-900, Brazil. 7.—e-mail: [email protected]
Er3+–Pr3+–Yb3+ co-doped LaNbO4 (LNO) phosphors were obtained by solidstate reaction and their up-conversion properties have been studied. The x-ray diffraction and Rietveld’s refinement revealed no evidence of significant structural changes or secondary phases in the synthesized materials. According to the up-conversion measurements, the observed emissions are due to Er3+ ions which are present as unintentional contaminant in the Pr3+ doped and Pr3+–Yb3+ co-doped systems. The intensity of all the bands was enhanced with increasing Yb3+ concentration, and at 8%Yb3+ a significant decrease of the green and red emissions was found due to the presence of cross-relaxation process between Er3+ and Pr3+ ions, mainly for green emissions because of the back energy transfer mechanisms from Er3+ to Yb3+. The Commission Internationale de l’e´clairage color coordinates of almost all samples were located in the green region, while for the LNO: Pr 0.1%–Yb8% phosphor they were located in the blue region. Red–Green–Blue phosphors were obtained from LaNbO4: Pr3+/Er3+/Yb3+ systems using the pair of activators Pr3+/Er3+ which is not commonly investigated in the literature. Key words: LaNbO4: Er3+/Pr3+/Yb3+, unintentional contaminant, up-conversion
INTRODUCTION Up-conversion (UC) luminescence has received more importance due to the possibility of applications in solar cells, medicine and optical communication.1–4 Up-conversion is a nonlinear anti-Stokes process in that the absorption of two or more low-
(Received October 17, 2019; accepted July 11, 2020)
energy photons results in the emission of a higher energy photon. In up-conversion processes it is very common to use lanthanide ions (Ln3+) because of their efficient UC energy transfer mechanisms and narrow emission and excitation bands with long lifetimes originating from electronic transitions f–f. These ions can be excited by the use of
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