resumo
Compounds with the general formula RE3MO7 (RE = rare earth ions; M = Ta, Nb, Sb, Ru, Ir, Os, Re, etc.), crystallize as a fluorite-related structure, forming polymorphs with different space groups. The space group strongly depends on the RE3+ and M5+ ionic radii and processing conditions. Structural characterization is well-established for the lanthanide series, but literature studies have divergent views about how to attribute yttrium tantalate (Y3TaO7) space groups-some authors have described the Y3TaO7 structure as orthorhombic and belonging to space group C222(1) or Ccmm, whereas others have assigned a cubic Fm (3) over barm structure to it. Here, we have characterized the structure of undoped and Eu3+-doped Y3TaO7 (0.1 to 50 mol% of Eu3+) samples synthesized by the sol-gel method that crystallized as a cubic disordered fluorite-type structure, space group Fm (3) over barm. Their powder X-ray diffraction measurements, Rietveld analyzes and Raman spectra were used as a conclusive technique of the structural properties. We have also investigated whether a secondary phase (M'-YTaO4) emerged in the samples and compared the phase composition of each sample to their Raman spectra. Low-temperature photoluminescence measurements (similar to 15 K) using Eu3+ as a structural probe helped us analyze the inhomogeneous broadening observed in the emission spectra. These measurements can be used as an important tool to attribute the crystalline phases of rare earth tantalates and niobates.
palavras-chave
X-RAY-DIFFRACTION; M = NB; RARE-EARTH; MAGNETIC-PROPERTIES; CRYSTAL-STRUCTURES; PHOTOLUMINESCENCE PROPERTIES; LUMINESCENCE PROPERTIES; RAMAN-SPECTROSCOPY; LOCAL-STRUCTURE; LN(3)NBO(7) LN
categoria
Chemistry
autores
Borges, FH; Guidorzi, MV; Labaki, HD; Ferreira, RAS; Gonçalves, RR
nossos autores
Maria Rute de Amorim e Sá Ferreira André
Professor Catedráticoagradecimentos
The authors want to acknowledge Brazilian funding agencies Fapesp, CNPq, and CAPES. FHB acknowledges FAPESP (grant numbers 2017/10424-3, 2018/04587-0, and 2020/00277-6) for the scholarships. MVG acknowledges CNPq for the scholarship process number 155872/2022-2. HPL acknowledges CAPES (grant number 88887.495267/2020-00) and FAPESP (2022/16692-8) for the scholarship. RRG acknowledges CNPq (grant number 303110/2019-8) and FAPESP (grant number 2020/05319-9 and 2021/08111-2) for financial support. We also would like to thank Mrs Cynthia Maria de Campos Prado Manso for reviewing the text. This work was also financed within the scope of the project CICECO-Aveiro Institute of Materials (UIDB/50011/2020 & UIDP/50011/2020), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership through European Regional Development Fund (ERDF) in the frame of Operational Competitiveness and Internationalization Programme (POCI).