Anti-Site Defects in Perovskite YAlO 3 :Ce Using Aberration-Corrected STEM Takayoshi Kishida, 1,2 Merry Koschan, 3 Mariya Zhuravleva, 3 Charles L. Melcher, 3 Gerd Duscher, 4 and Matthew F. Chisholm 2 1 Department of Technology Group, Analysis & Simulation Center, Asahi Kasei Corporation, 2-1 Samejima, Fuji, Shizuoka, 416-8501, Japan 2 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA 3 Scintillation Materials Research Center, University of Tennessee, Knoxville, TN 37996 USA 4 Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996 USA The aluminate perovskites YAlO 3 have been identified as potential scintillator materials due to their high light output and short decay time. However, the performance of YAlO 3 is still low. Despite the promising optical properties of YAlO 3 , it has been proposed that their potential as scintillators has not been fully realized[1]. Recently, the focus has been on carrier traps as the limiting factor in the performance of YAlO 3 , but the nature of these traps has not been identified. An investigation using first- principles calculations suggested that anti-site defects in which B-site Aluminum and A-site Yttrium are interchanged have a lower energy than Shottky or Frenkel defects[2,3]. Despite numerous studies, there is still no direct evidence to show the existence of anti-site defects. We have used a fifth-order aberration-corrected Nion UltraSTEM200 scanning transmission electron microscope to investigate the local atomic structure of YAlO 3 doped with 0.1% Ce. YAlO 3 :Ce 3+ are expected to have both types of cation anti-site defects (Al on the Y site and Y on the Al site). High- angle annular dark-field (HAADF) imaging was used to detect the presence of anti-site defects in YAlO 3 :Ce 3+ . A typical HAADF image from YAlO 3 :Ce 3+ is seen in Figure1b along with an image simulation based on the multi-slice method. The image was obtained at 200 kV using a probe convergence angle of 30 mrad. We can see some B-sites Al+O columns with brighter intensity as indicated by white circles and a blue arrow in Figure1b. And we also can see an A-site column with reduced intensity as indicated by a red arrow in Figure1b and as shown line profile in Figure 2. To interpret these intensity variations, HAADF image simulations using a structure with between 0-10% Y on the Al B-site and 0-10% Al on the A-site Y were performed. As shown in Figure 2, the experimental and simulated intensities at A-sites and B- sites with and without 10% anti-site defects are in good agreement. Additional details on these YAlO 3 :Ce crystals provided by DFT calculations and optical property measurements will be discussed. References [1] D.J.Singh et al., Phys. Rev. B 76 (2007) 214115. [2] Maja M Kuklja, J.Phys.:Condens. Matter 12 (2000) p.2953. [3] C.R.Stanek et al., J.Appl.Phys. 99 (2006) 113518. [4] This work was supported in part by the DOE Office of Basic Energy Sciences, Materials Sciences and Engineering Division (M.F.C.) and the U.S. Department of Energy, NA-22 under Grant DE- NA0000473. 132 doi:10.1017/S1431927614002384 Microsc. Microanal. 20 (Suppl 3), 2014 © Microscopy Society of America 2014