%0 Book Section
%T Caracterización de la solución sólida Na2(C03,S04) A 550°C
publisher Univ. Oviedo, Vicerrectorado de Extensión Universitaria
%D 1996
%U 8460552705
%@ https://hdl.handle.net/20.500.14352/60545
%X Although it is known that unlimited solid solution exists for the hightemperature polymorphs Na2S04 (1)and α-Na2C03 , the phase relationships and thevariation of crystallographic parameters for different compositions are not studied.Na2S04 has four well established modifications, but only the high temperaturemodification Na2S04 (1) (Pб3/mmc), stable above 237°C, forms extended solidsolution series with Na2C03. At the other extreme, Na2C03 shows three polymorphsand 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 fordifferent solid solution compositions. The study was carried out by X ray diffraction ina high temperature powder camera. The diffraction patterns show a continuousevolution through the entire compositional range. Crystalline spacings and cellparameters decrease as the sulphate content decreases. This fact and the unusualunlimited S04=-C03= substitution can be explained by the orientational disorder oftetrahedral and triangular groups. Theoretical powder diffraction diagrams, calculatedassuming this orientational and substitutional disorder, show a good fit with theexperimentalresults.
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