Structure, energy band, and optical properties of NaLa(PO{sub 3}){sub 4} crystal

• Published in: Journal of solid state chemistry Vol. 179; no. 2
• Main Authors: Zhu, J., Cheng, W.-D., Wu, D.-S., Zhang, H., Gong, Y.-J., Tong, H.-N.
• Format: Journal Article
• Language: English
• Published: United States 15.02.2006
• Subjects: ABSORPTION SPECTRA; EMISSION SPECTRA; INFRARED SPECTRA; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; LANTHANUM COMPOUNDS; LATTICE PARAMETERS; MONOCLINIC LATTICES; OPTICAL PROPERTIES; PHOSPHATES; SODIUM IONS; SPACE GROUPS; X-RAY DIFFRACTION
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2005.10.040

An alkali metal-rare earth phosphate crystal of NaLa(PO{sub 3}){sub 4} has been synthesized by high temperature solid-state reactions and structurally characterized by single crystal X-ray diffraction analysis, for the first time. It crystallizes in the monoclinic P2{sub 1}/n space group with lattice parameters: a=7.2655(3), b=13.1952(5), c=10.0760(1)A, {beta}=90.382{sup o}(1), V=965.96(5)A{sup 3}, Z=4. It is composed of LaO{sub 8} polyhedra and [(PO{sub 3}){sub 4}]{sup 4-} chains sharing oxygen atoms to form a three-dimensional framework, delimiting intersecting tunnels in which the sodium ions are located. The IR spectrum, absorption spectrum, and emission spectrum of the compound have been investigated. The absorption edge is located at 340nm (3.60eV). The calculated total and partial densities of states indicate that the top of valence bands is mainly built upon O-2p states which interact with P-3p states via {sigma} (P-O) interactions, and the low conduction bands mostly originates from unoccupied La-5d states. The P-O bond is mostly covalent in character, and the ionic character of the Na-O bond is larger than that in the La-O bond.