High temperature x-ray powder diffractometric studies of the superconducting compound YBa2Cu3O7-x from room temperature to 1300 K in air |
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| Affiliation: | 1. Department of Physics, Faculty of Sciences, Karadeniz Technical University, 61080, Trabzon, Turkey;2. Programme of Opticianry, Vocational School of Health Services, Artvin Çoruh University, 08000, Artvin, Turkey;3. Department of Physics, Faculty of Arts and Sciences, Recep Tayyip Erdoğan University, Rize 53100, Turkey;4. Department of Energy Systems Engineering, Faculty of Engineering and Architecture, Sinop University, Sinop 57000, Turkey;1. Department of Mathematics and Science Education, Faculty of Education, Bayburt University, 69000 Bayburt, Turkey;2. Department of Physics, Faculty of Science, Karadeniz Technical University, 61080 Trabzon, Turkey;3. Department of Physics, Faculty of Arts and Sciences, Recep Tayyip Erdogan University, 53100 Rize, Turkey;4. Department of Energy Systems Engineering, Faculty of Engineering and Architecture, Sinop University, 57000 Sinop, Turkey;1. NASA Goddard Space Flight Center, Greenbelt, MD, USA;2. Universities Space Research Association (USRA), Columbia, MD, USA;3. University of Maryland, College Park, MD, USA;1. Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, Zagreb 10000, Croatia;2. Department of Physics, University of Osijek, Trg Ljudevita Gaja 6, Osijek HR-31000, Croatia;3. Institute of Physics, Bijenička cesta 46, P. O. Box 304, Zagreb HR-10001, Croatia;4. Institute for Materials Research-UNAM, Ciudad Universitaria Coyoacan, Mexico D.F. C.P. 04510, Mexico |
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| Abstract: | At room temperature, the compound YBa2Cu3O7-x is orthorhombic, distorted perovskite, deficient in oxygen. X-ray powder diffractograms obtained for this compound over a range of temperatures between room temperature (298 K) and 1300 K in air reveal no change in X-ray diffraction pattern up to 1200 K except for slight shift in peak positions and variations in peak intensities because of thermal expansion and stoichiometry changes in oxygen or metal ion sub-lattices. At temperatures above ∼ 1250 K, the compund undergoes an irreversible transition to a new phase analogous to Y2BaCuO5 green phase which is an insulator. Temperature variation of lattice parameters shows an anisotropic expansion. Expansion along c-axis being maximum. Coefficients of linear thermal expansion along a and b axes are almost the same (δa≈δb≈7×10−6.K−1) while along c-axis it is double (δc≈15×10-6. K−1) than that of a or b. Coefficient of volume thermal expansion of the unit cell (δv≈29×10−6.K−1) obeys the relation δv≈δa+δb+δc for an orthorhombic symmetry in the range 298–1200K in air. |
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