2026-06-30T01:25:07Zhttps://docta.ucm.es/rest/oai/request

oai:docta.ucm.es:20.500.14352/605452024-07-22T18:15:35Zcom_20.500.14352_14col_20.500.14352_21

00925njm 22002777a 4500 dc López De Andrés, María Sol author Marcos Pascual, Celia author Cocaño Blanco, Susana author García Martínez, O. author Prieto Rubio, Manuel author 1996 Although it is known that unlimited solid solution exists for the high temperature polymorphs Na2S04 (1)and α-Na2C03 , the phase relationships and the variation of crystallographic parameters for different compositions are not studied. Na2S04 has four well established modifications, but only the high temperature modification Na2S04 (1) (Pб3/mmc), stable above 237°C, forms extended solid solution series with Na2C03. At the other extreme, Na2C03 shows three polymorphs and a rather complicated transition behaviour, being the hexagonal phase α-Na2C03 (Pб3/mmc)stable at T > 489°C. In this paper, the crystallographic parameters were determined at 550°C for different solid solution compositions. The study was carried out by X ray diffraction in a high temperature powder camera. The diffraction patterns show a continuous evolution through the entire compositional range. Crystalline spacings and cell parameters decrease as the sulphate content decreases. This fact and the unusual unlimited S04=-C03= substitution can be explained by the orientational disorder of tetrahedral and triangular groups. Theoretical powder diffraction diagrams, calculated assuming this orientational and substitutional disorder, show a good fit with the experimentalresults. 8460552705 https://hdl.handle.net/20.500.14352/60545 Caracterización de la solución sólida Na2(C03,S04) A 550°C