Crystal and Electronic Structure of (Y,Pr) x Sm 1x BO 3 Oxide OSMAN MURAT OZKENDIR, 1,4 H. GUNDOGMUS, 2 and CHATREE SAIYASOMBAT 3 1.—Faculty of Technology, Energy Systems Engineering, Mersin University, 33400 Tarsus, Turkey. 2.—Faculty of Engineering, Hakkari University, 30000 Hakkari, Turkey. 3.—Syn- chrotron Light Research Institute (Public Organization), P.O. Box 93, Nakhon Ratchasima 30000, Thailand. 4.—e-mail: ozkendir@gmail.com The effects of Y and Pr substitution on the electronic and crystal structure of triclinic SmBO 3 have been investigated using x-ray diffraction (XRD) analysis and x-ray absorption fine-structure spectroscopy. Polycrystalline structure was observed on substitution of Y 3+ and Pr 4+ ions with Sm 3+ coordination. Yttrium-substituted samples were found to contain BO 3 ligands around Sm atoms, while the crystal structure of YBO 3 presented hexagonal geometry, not preserving the triclinic crystal structure. Also, praseodymium ions (Pr 4+ ) formed isolated Pr 2 B 5 crystal structure by distorting some BO 3 ligands. Moreover, electronic structure studies revealed that 4f levels of Sm and Pr were inactive in bonding interaction and did not support strong coupling be- tween neighboring Sm and Y/Pr atoms. Key words: Absorption spectroscopy, electronic structure, crystal properties, oxides INTRODUCTION Due to their good chemical stability and excellent optical properties with thermal stability, rare-earth orthoborates (REOs) are of great importance for use in recent technological applications. In particular, their exceptional optical damage threshold and high ultraviolet transparency have created huge demand for use in research on gas discharge panels. 1–3 Triclinic SmBO 3 material, which is the parent material for this study, is a member of the REO family, exhibiting enhanced optical properties for use in near-infrared lasers or in stealth technology as a radar absorber. 4–7 Several studies have hinted that the source of the desirable properties of REO materials is their narrow band structure and the rich quantum symmetry of the 4f levels, enhancing their role in molecular reactions, whereas other studies have revealed the significance of the f-level activity in molecular interplay during bonding through hybridization between 4f electrons and conduction bands. 8,9 In this study, the effects of substitution of Y (yttrium) and Pr (praseodymium) on the crystal and electronic properties of samarium orthoborate (SmBO 3 ) with triclinic structure were investigated. The general formula of the investigated compounds is (Y,Pr) x Sm 1x BO 3 , where boron is considered to play a significant role due to its higher affinity as well as high electron deficiency with highly vacant p-orbital. Furthermore, their thermal stability makes borates notable candidate materials for use in high-temperature devices and as nonlinear opti- cal materials. 10 In the SmBO 3 structure, the boron atoms are strongly connected with oxygen atoms to form BO 3 ligands that link the Sm atom with the oxygen atoms. Therefore, samarium orthoborate materials can be considered to comprise two parts, viz. Sm and BO 3 ligands. The parent oxide SmBO 3 is a member of the rare- earth orthoborate family with general formula (RE) 3+ BO 3 and has been intensively studied in related fields. The crystal structure of samarium orthoborate samples has been reported to exhibit two different geometries: (1) hexagonal in space group (SG) P63/mmc and (2) triclinic in SG P1. 11,12 Materials of the (RE) 3+ BO 3 family are popular due (Received August 19, 2017; accepted December 2, 2017; published online December 13, 2017) Journal of ELECTRONIC MATERIALS, Vol. 47, No. 3, 2018 https://doi.org/10.1007/s11664-017-6010-y Ó 2017 The Minerals, Metals & Materials Society 2050