Abstract
The phase diagram in the system La-Se was investigated around the LaSe2 composition. X-ray and microprobe analyses reveal the existence of only two phases, LaSe2 and LaSe1.9, with no solid solution behavior between them. Infrared and Raman spectra of the non-stoichiometric phase suggest that the vacancies in the basal plane of the low-dimensional lattice are disordered. Polarized single crystal Raman spectra and a modified valence force field calculation for LaSe2 indicate that the assumption of isolated (Se-Se)2- pairs in the anti-Fe2As structure is not justified. In accord with this, the observed resistivity for LaSe2 as a function of temperature is typical of a semimetallic compound. A transition to a semiconductor may occur below 110K. The measured resistivity as a function of temperature for the non-stoichiometric LaSe1.9 phase is indicative of a semiconductor. The infrared data together with the electrical measurements suggest that this phase can be considered as n-type semiconductor with the holes in the anionic sp valence bands.
Original language | English (US) |
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Pages (from-to) | 1625-1634 |
Number of pages | 10 |
Journal | Journal of Physics and Chemistry of Solids |
Volume | 57 |
Issue number | 11 |
DOIs | |
State | Published - Nov 1996 |
Keywords
- A. chalcogenides
- C. Raman spectroscopy
- C. infrared spectroscopy
- D. crystal structure
- D. electrical properties
ASJC Scopus subject areas
- General Chemistry
- General Materials Science
- Condensed Matter Physics