Microstructural and Thermal Characterization of Basic and Stoichiometric Lithium Phosphates, in Relation with Their Catalytic Activity

✍ Scribed by R.M. Rojas; J.L.Martin De Vidales; A. Delgado; J.V. Sinisterra

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 478 KB
• Volume: 106
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1284

✦ Synopsis

A comparative study of basic and stoichiometric lithium phosphates has been carried out by thermal analysis, X-ray powder diffraction, and IR spectroscopy. Structural and microstructural characterization, carried out by the Rietveld method and a profile-fitting procedure for analysis of broadened (\mathrm{X})-ray diffraction peaks, reveal that, unlike stoichiometric material, basic lithium phosphate shows a very isotropic and homogeneous crystallite size distribution (mean size (225 \AA) ). They are justified in terms of the synthesis procedure followed in the preparation of both phosphates. (\beta \rightarrow \gamma-\mathrm{Li}{3} \mathrm{PO}{4}) transition in the catalyst is shifted up to (670^{\circ} \mathrm{C}) and takes place as an exothermic reaction associated with a dramatic diminution of the surface area ( 45 to (2 \mathrm{~m}^{2} / \mathrm{g}) ). The high surface area and the presence of solvated excess lithium cations, both being a consequence of the synthesis procedure, accounts for the catalytic activity shown by the nonstoichiometric lithium phosphate. 1993 Academic Press, Inc.