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High-pressure structural studies of Li x La1/3NbO3 (x = 1/6, 1/3, 1/2, 2/3) |
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| Authors: | O Noked A Melchior R Shuker S Chizawa H P Liermann B J Kennedy M Nakayama E Sterer |
| Institution: | 1. Physics Department, Nuclear Research Centre, Negev, PO Box 9001, 84109, Beer Sheva, Israel 2. Physics Department, Ben-Gurion University, 84105, Beer Sheva, Israel 3. Department of Material Science and Engineering, Nagoya Institute of Technology, Showa, Nagoya, Japan 4. Petra III, P02, Deutsches Elektronen Synchrotron, Notkestr. 85, 22607, Hamburg, Germany 5. School of Chemistry, The University of Sydney, Sydney, NSW, 2006, Australia 6. Physics Department, Harvard University, 19 Oxford St., Cambridge, MA, 01238, USA |
| Abstract: | The high-pressure behavior of Li x La1/3NbO3 (x = 1/6, 1/3, 1/2, 2/3) perovskites where Li cations were substituted for the existing vacancies was studied using synchrotron X-ray diffraction. It was shown that all these materials undergo irreversible pressure-induced amorphization around 14.5 GPa regardless of the Li concentration. The Li-inserted materials were found to exhibit a standard pressure response (bulk modulus pressure derivative B 0′ ~4) when in the crystalline phase, whereas La1/3NbO3 shows a linear volume contraction versus pressure, i.e., B 0′ ~(?1). These results suggest that the structural collapse is not a consequence of cation disorder resulting from the Nb atoms (B-site) migrating to the A-site vacancies. The observed pressure response can be understood by increased occupancy of the A-sites opposing the tilting of the NbO6 octahedra. The pressure evolution of the Nb oxidation state is discussed. |
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