Electronic Structure Characterization of the Bi-YIG by EELS-STEM N. Herrera-Pineda 1* , M. García-Guaderrama 2 , G. Herrera-Pérez 3* , M. E. Fuentes-Montero 1 , J. M. Napóles-Duarte 1 , J. P. Palomares-Baez 1 , C. Ornelas-Gutierrez 4 , R. Ochoa-Gamboa 4 , W. Antunez-Flores 4 1. Facultad de Ciencias Químicas, Universidad Autónoma de Chihuahua, Circuito Universitario s/n campus II, Chihuahua, Chih. 31125, Mexico. 2. Laboratorio de Materiales y Sistemas Fotosensibles, CUCEI, Universidad de Guadalajara, Av. José Guadalupe Zuno # 48, Industrial los Belenes, Zapopan, Jalisco 45100, Mexico. 3. Catedrático CONACyT, Centro de Investigación en Materiales Avanzados S. C. Miguel de Cervantes 120, Chihuahua, Chih. 31136, México. 4. Laboratorio Nacional de Nanotecnología, Centro de Investigación en Materiales Avanzados S. C. Miguel de Cervantes 120, Chihuahua, Chih. 31136, México. * Corresponding author: nherrerap@uach.mx, guillermo.herrera@cimav.edu.mx The present study monitored the electronic structure (multiplet structure) of a ceramic material with garnet structure BiY2Fe5O12 (Bi-YIG) that has important magneto-optical properties [1,2]. There are few studies regarding the electronic structure characterization obtained by electron energy loss spectroscopy (EELS). The motivation of this work is to present the EELS of Bi-YIG and its interpretation of the local electronic structure through the Fe L2.3 -edge. This interpretation is based on the multiplet calculation using the modified Hartree-Fock method that includes the crystal field and charge transfer effects [3]. The Bi-YIG was prepared by the sol-gel method via combustion and heat treated at 1000 o C [4]. The powders were dispersed in isopropanol and deposited on the lacey carbon films on a 300mesh copper TEM grid. A JEM-2200FS microscope operated at 200 kV was used for a microstructural and structural study. The last one was determined by the selected area of electron diffraction (SAED) characterization using the ICSD No. 2012; for the average grain size and shape was obtained with the analysis on five field emission scanning electron (FE-SEM model JSM-7401F) micrographs through the ImageJ software [5]. The EELS spectra were collected in a Phillips CM200 microscope that has a PEEL766 system worked at 200 kV. Figure 1(a) shows SAED pattern with its indexing using the Process diffraction software [6]. The results are associated with a garnet-type structure with cubic phase and spatial group Ia-3d (No. 230). The SEM characterization reveals non-uniform faceted grains with polygonal shape with an average grain size around 3 microns as one can observe in panel (b) of Figure 1. The EELS spectra were analyzed in the valence region (VEELS) as well as in the core region (CEELS). Figure 1(c) shows the VEELS spectrum. It can be observed the elastic peak and the bulk plasmon centered at 21 eV. It can be notice also, the O4.5-edge of bismuth is centered at 28 eV. Figure 2(a) shows the core region and the respective Y M4,5-edge and Y M2,3-edge. The O K-edge (530 eV) is presented in panel b. The crystal field value used in the calculations takes into account 10Dq = 1.2 eV for octahedral sites and 10 Dq = -0.6 for tetrahedral sites. The core-hole lifetime for L3 and L2 edge were broadened by Lorentzian of  = 0.36 and 0.37, respectively. The resulting spectrum was convoluted with a Gaussian function width of 1.0 eV to take into account the instrumental broadening. The comparison between the L2,3-edge of iron with calculated spectrum related to the sum of the contributions of Fe 2+ in octahedral Oh (d 6 Oh) symmetry, Fe 3+ , Oh (d 6 Oh) and Fe 3+ tetrahedral Td (d 5 Th) symmetry is shown in panel c. The present results agree with those reported that the Fe 2+ and Fe 3+ cations at the octahedral sites are 666 doi:10.1017/S1431927619004069 Microsc. Microanal. 25 (Suppl 2), 2019 © Microscopy Society of America 2019 https://doi.org/10.1017/S1431927619004069 Downloaded from https://www.cambridge.org/core. IP address: 196.16.16.207, on 07 Aug 2019 at 10:14:49, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms.