The present work investigates in-situ the thermal behaviour of alum-(Rb), RbAl(SO4)2 · 12H2O, by high-temperature X-ray powder diffraction from 303 K to melting, which starts at 359 K and is completed, due to kinetics, at 363 K. The calculated a0 linear thermal expansion coefficient is 10.33(12) x 10-6 K-1 within the investigated thermal range. The k order parameter, which is the measure of the extension of the orientational disorder of the sulphate group, decreases from ca. 0.80 at 303 K to ca. 0.75 just before melting. This behaviour has been shown to depend on the need to keep the bond valence sum of the Rb+ cation, which coexists in both six- and seven-fold coordination, at a reasonable value of ca. 0.82 valence units.

Thermal behaviour of alum-(Rb) RbAl(SO4)2 · 12H2O from in-situ laboratory high-temperature X-ray powder diffraction data / Ballirano, Paolo. - In: PERIODICO DI MINERALOGIA. - ISSN 0369-8963. - 84:2(2015), pp. 233-246. [10.2451/2015PM0002]

Thermal behaviour of alum-(Rb) RbAl(SO4)2 · 12H2O from in-situ laboratory high-temperature X-ray powder diffraction data

BALLIRANO, Paolo
2015

Abstract

The present work investigates in-situ the thermal behaviour of alum-(Rb), RbAl(SO4)2 · 12H2O, by high-temperature X-ray powder diffraction from 303 K to melting, which starts at 359 K and is completed, due to kinetics, at 363 K. The calculated a0 linear thermal expansion coefficient is 10.33(12) x 10-6 K-1 within the investigated thermal range. The k order parameter, which is the measure of the extension of the orientational disorder of the sulphate group, decreases from ca. 0.80 at 303 K to ca. 0.75 just before melting. This behaviour has been shown to depend on the need to keep the bond valence sum of the Rb+ cation, which coexists in both six- and seven-fold coordination, at a reasonable value of ca. 0.82 valence units.
2015
X-ray powder diffraction; Rietveld method; thermal behaviour; alum-(Rb)
01 Pubblicazione su rivista::01a Articolo in rivista
Thermal behaviour of alum-(Rb) RbAl(SO4)2 · 12H2O from in-situ laboratory high-temperature X-ray powder diffraction data / Ballirano, Paolo. - In: PERIODICO DI MINERALOGIA. - ISSN 0369-8963. - 84:2(2015), pp. 233-246. [10.2451/2015PM0002]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/782170
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