SrAl 12 O 19 :Pr 3+ nanodisks and nanoplates: New processing technique and photon cascade emission
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Jiahua Zhanga) and Xia Zhang Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
Ki-Soo Limb) BK21 Physics Program and Department of Physics, Chungbuk National University, Cheongju 361-763, Korea (Received 27 October 2008; accepted 13 January 2009)
High-quality SrAl12O19:Pr3+ nanodisks and nanoplates were fabricated via a new processing technique based on a modified polymer steric entrapment method. Serious agglomeration and large particle size distribution of final products, which usually occurred in the conventional method, were eliminated completely. The effects of new synthetic processes on the morphology, crystallization, and yield of products and the relevant mechanisms were discussed. As far as we know, SrAl12O19:Pr3+ nanodisks with mean diameter 60 nm and thickness between 5 and 10 nm were successfully synthesized for the first time by this low-cost technique. The new synthetic method may provide a general route to synthesize other refractory mixed-oxide nanocrystals. Photon cascade emission involving transitions 1S0–1I6 followed by 3P0–3H4 in SrAl12O19:1% Pr3+ nanodisks was investigated. Size-effect-induced blue shift of the 4f5d states of Pr3+ was observed in SrAl12O19:1% Pr3+ nanodisks, in which the quantum efficiency was preserved, as in the bulk counterparts. I. INTRODUCTION
Rare earth doped oxide nanocrystalline phosphors attract considerable attention because of their potential application in lighting and display. With the progress of nanoscience, people are now equipped with various fabrication methods with novel properties on the nanoscale level. These so-called “size-dependent properties” are of great interest and significance. However, the processing methods necessary to produce high-crystallization phosphor, which usually helps to achieve high luminous efficiency, generally involve processing at high temperature, which tends to agglomerate the primary crystallites and thus lose the possible benefits of the nanosize materials. Furthermore, the quantum efficiency (QE) of oxide phosphors fabricated in nanosize regime is usually much lower than their microsize counterparts due to surface effects. They are always assumed as the main hindrances to their practical applications.1–5 Thus, much attention should be paid to developing more new Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2009.0193 J. Mater. Res., Vol. 24, No. 5, May 2009
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methods to control the morphology of the nanoparticles and preserve their QEs. Some refractory mixed oxides, such as SrAl12O19 (SAO; melting point > 1800 C) or other strontium aluminates, have significant technological importance because of their unique combination of mechanical, thermal, and optical properties, making them candidates for industries of lighting and displays,6 laser,7,8 cement, and even steel.9,10 Despite their impor
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