Ce 3+ /Tb 3+ activated GdF 3 , KGdF 4 , and CeF 3 submicro/nanocrystals: Synthesis, phase evolution, and optical propert

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Hyun Kyoung Yang, Jong Won Chung, Byung Kee Moon, Byung Chun Choi, and Jung Hyun Jeonga) Department of Physics, Pukyong National University, Busan 608-737, Korea

Kwang Ho Kim School of Materials Science and Engineering, Pusan National University, Busan 609-735, Korea (Received 23 June 2011; accepted 11 October 2011)

Based on a citric acid-assisted hydrothermal method, series of Ce3+/Tb3+ activated fluorides have been synthesized. By controlling the amount of KNO3, the final products evolve from the Ce3+/Tb3+ codoped orthorhombic phase GdF3 to the Ce3+/Tb3+ codoped cubic phase KGdF4. The concentration of Ce3+ has great effects on the crystalline phases and the morphologies of final products. The Ce3+ concentration dependent samples illustrate the appearance of the hexagonal phase solid solution CeF3–GdF3–TbF3 in the final products. When the Ce3+ concentration is 20 mol%, the sample Ce20 presents the hexagonal phase CeF3 but the diffraction peaks move to higher degree. The x-ray diffraction patterns suggest the phase evolution of final products, the field emission scanning electron microscopy images present the variation in morphology of samples, and the photoluminescence excitation and emission spectra as well as the luminescent dynamic curves illustrate the optical properties of samples.

I. INTRODUCTION

In last few decades, rare earth compounds have been extensively studied for their practical and potential applications.1–4 Among them, the fluorides are now receiving wide attention owing to the low-frequency phonons usually observed in their crystal lattices as well as in their thermal and environmental stabilities.5,6 The fluoride host materials with the composition MGdF4 (M 5 Li, Na, or K) are of particular interest.7–11 Recently, the RE3+ doped KF–GdF3 system has received more attention due to both its structural and optical properties.12–15 In addition, Gd3+ is an ideal paramagnetic relaxation agent used in magnetic resonance imaging.16,17 Therefore, the RE3+ doped KF–GdF3 system is very attractive to produce single phase multifunctional materials. Researchers have developed various synthetic strategies for the synthesis of reproducible and controllable materials. Especially, high-quality (such as monodisperse, single-crystalline, well-shaped, and phase-pure) fluorides have been fabricated successfully due to their potential applications in biology and medicine.18–20 As a typical solution approach, the hydrothermal treatment has been proven to be effective and convenient in a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.388 2916

J. Mater. Res., Vol. 26, No. 23, Dec 14, 2011

http://journals.cambridge.org

Downloaded: 29 Jan 2015

preparing various inorganic materials with diverse controllable morphologies and architectures.21 In addition, the hydrothermal method is relatively simple, mild, easy, and green to produce a large amount of products; therefore, the hydrothermal route is often adopted to synthesize fluoride host materials. In the hydrothermal synthesis, there a

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