Effect of (Pr-Yb) Co-doping on the Luminescence and Dielectric Behaviour of LaNbO 4 Ceramic

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https://doi.org/10.1007/s11664-020-08339-9  2020 The Minerals, Metals & Materials Society

Effect of (Pr-Yb) Co-doping on the Luminescence and Dielectric Behaviour of LaNbO4 Ceramic J.P.C. DO NASCIMENTO ,1,5,7 R.G.M. OLIVEIRA,3,5 F.F. DO CARMO,2,5 J.E.V. DE MORAIS,3,5 J.C. SALES,4,5 M.A.S. SILVA,5 D.X. GOUVEIA,1,5 ´ NIOR,6 and A.S.B. SOMBRA5,6 H.D. DE ANDRADE,6 I.S. QUEIROZ JU 1.—Instituto Federal de Educac¸a˜o, Cieˆncia e Tecnologia do Ceara´, PPGET, Fortaleza, CE, Brazil. 2.—Departamento de Quı´mica Orgaˆnica e Inorgaˆnica, Centro de Cieˆncias, Universidade Federal do Ceara´ (UFC), Fortaleza, CE, Brazil. 3.—Departamento de Engenharia de Teleinforma´tica (DETI), Universidade Federal do Ceara´, UFC, Fortaleza, CE, Brazil. 4.—Centro de Cieˆncias Exatas e Tecnologia, Universidade Estadual Vale do Acarau´ (UVA), Campus da Cidao, Sobral, CE, Brazil. 5.—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, Brazil. 7.—e-mail: [email protected]

This paper analysed the effects of doping with Pr and Yb on the dielectric and down-conversion luminescence properties in the ceramic matrix LaNbO4. Xray diffraction analysis showed that no additional phases were present in the materials. Impedance spectroscopy analysis demonstrated increasing conductivity due to the generation of oxygen vacancy, and other charge carriers caused by the change in the oxidation states of Pr as well as by lattice distortion caused with the insertion of Pr and Yb ions. Down-conversion measurements in 470 nm presented well-defined bands in the red region that decreased in intensity with the enhancement of Yb3+. Results obtained demonstrate that Pr-Yb co-doped LaNbO4 (LNO) could be used both in electrical and optical applications. Key words: LaNbO4, doping, dielectric properties, down-conversion luminescence

INTRODUCTION The ortho-niobates ceramic family with the formula ANbO4 is a class of compounds with interesting properties that permit different applications such as thermometry, light emitting diodes (LEDs), and sensors, amongst others.1–5 These materials undergo a phase transition from the monoclinic fergusonite to the tetragonal scheelite structure in the range of 773–1123 K, depending on the rareearth ions present in the A-site.6,7 Among the elements of this family, lanthanum ortho-niobate (LaNbO4) presents good mechanical behaviour and dielectric and proton conduction properties. All these properties make LaNbO4

(Received November 5, 2019; accepted July 16, 2020)

(LNO) an interesting material for several technological applications, such as solid oxide fuel cells (PC-SOFCs). However, it is necessary to improve the conductivity of LaNbO4 to employ this material in PC-SOFCs, which can be obtained through modifications in their lattice.8–10 In addition, LNO ceramic has high thermal and chemical stability and moderated phonon energy ( 800 cm1) that allows this material can be used as

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