Reversion of Incommensurate Modulation in Cubic Lazurite: Example of Reversible Forced Equilibrium?

Vladimir L. Tauson^*, Anatoly N. Sapozhnikov, Ekaterina V. Kaneva, Sergei V. Lipko

A. P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, Irkutsk, Russia.

DOI: 10.4236/nr.2014.512065                

Abstract

The sample of cubic lazurite, collected in the Baikal region, with incommensurately 3D modulated (ITM) structure has been studied by the method of high-temperature X-ray powder diffraction. At short time of annealing in high-temperature diffraction experiment the modulation recovery proceeds during cooling down the sample to room temperature. The identity of the period of both initial and recovered modulation demonstrates that the system has a structural memory. The acquired results are interpreted through comparison of thermal behavior of lazurite, sodalite and quartz structures. It is supposed that two kinetically different and thermally activated processes proceed under heating: 1) reversible framework expansion due to Si-O-Al angle increase, and 2) equalizing of periodic local distortions via the diffusion-controlled transfer of cage ions between adjacent subcells. The second process seems to be much slower than the first one, especially at lower temperatures. With increasing temperature, both processes are activated. However, the framework expands more rapidly than the cage clusters migrate, and the periodic distortions of the framework are aligned. Under lower temperatures, the framework shrinks and again accommodates to the configuration of cage cations (clusters), which may be changed at high temperature and sufficient time or may not at lower temperature, short time, unfavorable SO2 fugacity values. In the first case the modulation disappears entirely, while in the second case it arises again. The probable reason for ITM formation is the balance of counteracting energetic terms: the elastic strain energy of structure deformation and the energy of cluster ordering providing the state of forced equilibrium. The excess free energy due to structure distortion is compensated by the increment associated with the cluster ordering process. However, no significant variations in sulphur anion speciation for different degrees of modulation retention were observed by XPS S 2p. This may be due to the ordering of Na- and Ca-containing clusters rather than the clusters with different sulphur species. ITM reversion is considered as an example of reversible forced equilibrium with completely reproducible forcing factor.

Keywords

Lazurite, High-Temperature X-Ray Diffraction, Incommensurate Modulation, Reversion Mechanism, Forced Equilibrium, Sulphur Speciation

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Cowley, J.M. (1979) What Are Modulated Structures? In: Cowley, J.M., et al., Eds., Modulated Structures, No. 9, American Institute of Physics, New York, 3-9.
[2]	Organova, N.I. (1989) Crystal Chemistry of Incommensurate and Modulated Mix-layered Minerals. Nauka, Moscow. (In Russian)
[3]	Sapozhnikov, A.N. (1990) Indexing of Extra Reflections in Powder Patterns of Lazurite in Connection with Structure Modulation Study. Zapiski Vserossiiskogo Mineralogicheskogo Obchshestva, 1, 110-116. (In Russian)
[4]	Sapozhnikov, A.N., Ivanov, V.G., Medvedev, A.Ya. and Matveeva, L.N. (1991) Influence of Thermal Treatment on Parameters of Modulated Structure of Cubic Lazurite from Baikal. Izvestia Academii Nauk SSSR Neorganicheskie Materiali, 27, 811-815. (In Russian)
[5]	Hassan, I. (2000) Transmission Electron Microscopy and Differential Thermal Studies of Lazurite Polymorphs. The American Mineralogist, 85, 1383-1389.
[6]	Tauson, V.L., Akimov, V.V., Sapozhnikov, A.N. and Kuznetzov, K.E. (1998) Investigation of the Stability Conditions and Structural-Chemical Transformations of Baikal Lazurite. Geochemistry International, 36, 717-733.
[7]	Tauson, V.L. and Sapozhnikov, A.N. (2005) Stability of the Modulated Structure of Baikal Lazurite and its Recrystallization at a Temperature of 600°C over a Wide Range of Sulfur Dioxide Fugacities. Crystallography Reports, 50, S1S9. http://dx.doi.org/10.1134/1.2133964
[8]	Tauson, V.L., Sapozhnikov, A.N., Shinkareva, S.N. and Lustenberg, E.E. (2009) The Nature of the Stability of an Incommensurate 3D Structural Modulation in Baikal lazurite: Experimental Data at 550°C. Geochemistry International, 47, 815-830. http://dx.doi.org/10.1134/S0016702909080059
[9]	Tauson, V.L., Sapozhnikov, A.N., Akimov, V.V., Lipko, S.V., Shinkareva, S.N. and Lustenberg, E.E. (2010) Modulated Cubic Lazurite from the Baikal Region: Structure Transformed to the State of Forced Equilibrium. Doklady Earth Sciences, 433, 931-936. http://dx.doi.org/10.1134/S1028334X10070196
[10]	Depmeier, W. (2005) The Sodalite Family—A Simple but Versatile Framework Structure. Reviews in Mineralogy & Geochemistry, 57, 203-240. http://dx.doi.org/10.2138/rmg.2005.57.7
[11]	Moulder, J.F., Stickle, W.F., Sobol, P.E. and Bomben, K.D. (1992) Handbook of X-Ray Photoelectron Spectroscopy. Perkin-Elmer Corporation, Eden Prairie.
[12]	Tauson, V.L., Goettlicher, J., Sapozhnikov, A.N., Mangold, S. and Lustenberg, E.E. (2012) Sulphur Speciation in Lazurite-Type Minerals (Na,Ca)8[Al6Si6O24](SO4,S)2 and Their Annealing Products: A Comparative XPS and XAS Study. European Journal of Mineralogy, 24, 133-152. http://dx.doi.org/10.1127/0935-1221/2011/0023-2132
[13]	Pynn, R. (1979) Incommensurable Structures. Nature, 281, 433-437. http://dx.doi.org/10.1038/281433a0
[14]	Tauson, V.L. and Akimov, V.V. (1997) Introduction to the Theory of Forced Equilibria: General Principles, Basic Concepts, and Definitions. Geochimica et Cosmochimica Acta, 61, 4935-4943. http://dx.doi.org/10.1016/S0016-7037(97)00348-7
[15]	Hassan, I. and Buseck, P.R. (1989) Cluster Ordering and Antiphase Domain Boundaries in Hauyne. The Canadian Mineralogist, 27, 173-180.
[16]	Hassan, I. and Buseck, P.R. (1989) Incommensurate-Modulated Structure of Nosean, a Sodalite-Group Mineral. The American Mineralogist, 74, 394-410.
[17]	Dempsey, M.J. and Taylor, D. (1980) Distance Least-Squares Modeling of the Cubic Sodalite Structure and of the Thermal Expansion of Na8(Al6Si6O24)I2. Physics and Chemistry of Minerals, 6, 197-208. http://dx.doi.org/10.1007/BF00309856
[18]	Hassan, I. and Grundy, H.D. (1984) The Crystal Structures of Sodalite-Group of Minerals. Acta Crystallographica Section B, 40, 6-13. http://dx.doi.org/10.1107/S0108768184001683
[19]	Liebau, F. (2003) Ordered Microporous and Mesoporous Materials with Inorganic Hosts: Definitions of Terms, Formula Notation, and Systematic Classification. Microporous and Mesoporous Materials, 58, 15-72. http://dx.doi.org/10.1016/S1387-1811(02)00546-2