Correlation Between the Stability of Carbonates in Ternary $Ln_2O_3-H_2O-CO_2$ Hydrothermal Systems and Lanthanide Systematics

Kutty, TRN and Tareen, JAK and Mohammed, Iftiqhar (1985) Correlation Between the Stability of Carbonates in Ternary $Ln_2O_3-H_2O-CO_2$ Hydrothermal Systems and Lanthanide Systematics. In: Journal of the Less-Common Metals, 105 (2). pp. 197-209.

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Abstract

Phase diagrams for ternary $Ln_2O_3-H_2O-CO_2$ systems for the entire lanthanide series (except promethium) were studied at temperatures in the range 100–950 °C and pressures up to 3000 bar. The phase diagrams obtained for the heavier lanthanides are far more complex, with the appearance of a number of stable carbonate phases. New carbonates isolated from lanthanide systems (Ln ≡ Tm, Yb, Lu) include $Ln_6(OH)_4(CO_3)_7,$ $Ln_4(OH)_6-(CO_3)_3,$ $Ln_2O(OH)_2CO_3,$ $Ln_6O_2(OH)_8(CO_3)_3$ and $Ln_{12}O_7(OH)_{10}(CO_3)_6. $ Stable carbonate phases common to all the lighter lanthanides are hexagonal $LnOHCO_3$ and hexagonal $Ln_2O_2CO_3.$ $Ln_2(CO_3)_3·$ $3H_2O$ is stable from samarium onwards and orthorhombic $LnOHCO_3$ is stable from gadolinium onwards. On the basis of the appearance of stable carbonates, four different groups of lanthanides were established: lanthanum to neodymium, promethium to europium, terbium to erbium and thulium to lutetium. Gadolinium is the connecting element between groups II and III. This is in accordance with the tetrad classification for f transition elements.

Item Type:	Journal Article
Publication:	Journal of the Less-Common Metals
Publisher:	Elsevier
Additional Information:	Copyright of this article belongs to Elsevier.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	16 Jul 2008
Last Modified:	19 Sep 2010 04:47
URI:	http://eprints.iisc.ac.in/id/eprint/14998

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