Y. Masuda, W. Morita, A. Yahata
Sep 7, 1998
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Influential Citations
3
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Journal
Thermochimica Acta
Abstract
Abstract The thermal phase transition of rubidium formate, observed at 363 K, was studied by means of thermal analysis and X-ray diffraction method. The transition was found to be a reversible first-order transition. In the phase transition, the orthorhombic phase ( Pca 2 1 ) with lattice constants a =9.229(1), b =4.630(2) and c =7.408(2) A, was transformed to the monoclinic phase ( P 2 1 / m ) with one of a =4.6552(4), b =4.6528(7), c =7.5170(6) A and γ =97.610(6)°. The values of the enthalpy, Δ H tr , and entropy change, Δ S tr , for the transition were 0.42±0.02 kJ mol −1 and 1.16±0.05 J K −1 mol −1 , respectively. Although the relative positions of rubidium atoms hardly changed in the phases before, and after, the transition, the orientation of formate ions differed in both the phases. The values of Δ H tr and Δ S tr seem to reflect a slight change of structure in the orientation of formate ions.