Microstructure effects in solid-state photoluminescent properties of lanthanide doped CaWO4 sheelite

GOMEZ, GERMAN E.; CARLOS A. LOPEZ; AYSCUE, RUSSELL LEE; TORRES DELUIGI, MARÍA DEL ROSARIO; KNOPE, KARAH; GRISELDA E. NARDA

Buenos Aires

Congreso; XIV Reunión Anual de la Asociación Argentina de Cristalografía; 2018

Comisión Nacional de Energía Atómica

During the last decades, lanthanides ions have been used as components for the development of optically active materials for emerging applications[1]. Moreover, the sheelite structure has been used as ?host-matrix? for lanthanides with emissions in visible and NIR region [2]. Ca1-2xLnxNaxWO4 samples with x = 0 and 0.1 and Ln = Eu and Sm, (bulk samples 1 and 2) were obtained as crystalline white powders applying a mechanothermal method. After that the samples were calcined at 700 °C obtaining the pure scheelite structure. In order to get nanoparticles a re-milling was performed. These samples (1NP and 2NP) were used for photoluminescence (PL) studies.The X-ray powder diffraction (XRPD) characterizations showed a tetragonal symmetry with I41/a (88) space group. Also, the milled samples were refined taking special attention in the broadening line. From the Rietveld method, using Fullprof,[3] the line shape was modelled using the Thompson-Cox-Hastings pseudo-Voigt function. The crystallite size (~18 nm) was highly reduced respect to bulk samples. From the PL studies of 1NP and 2NP, the 4G5/2 → 6HJ and 5D0 → 7FJ transitions were located respectively. Moreover, the Eu-intrinsic and overall quantum yields (QYEu and QYoverall) for compound 1NP showing values of 27.1% and 2.08% respectively, indicating promising emission performance with low doping values. Besides the quantification of luminescence through the calculation of the CIE x,y chromaticities was made, exhibiting red and orange emissions (Figure 1). These result open up the potential applications of 1NP and 2NP in the sensing field.[1] J.-C. G. Bünzli, C. Piguet, Chem. Soc. Rev., 2005. [2] J.Liu, A. M. Kaczmarek, J. Billet, I. Van Driessche, R. Van Deun, Dalton Trans., 2016,45, 12094-12102. [3] (a) H. M. Rietveld, J. Appl. Crystallogr. 1969, 2, 65?71; (b) J. Rodríguez-Carvajal, Phys. B 1993, 192, 55?69.