Abstract
Lattice parameters, and intensities of selected X-ray reflexions, have been measured as a function of temperature for natural leucite, to characterise the phase transformation behaviour. At low temperatures leucite has a large ferroelastic distortion, but the temperature evolution of lattice parameters cannot be explained in terms of a purely ferroelastic phase transition; in particular, the considerable change in volume with temperature implies an additional transition mechanism, which we correlate with off-centring of K-ions in the low-temperature phase, and a collapse of the 〈111〉 structural channels. The transition behavior can therefore be rationalised in terms of two competing mechanisms: (I) Ferroelastic (consistent with the change m3m→ 4/mmm); (II) Volume-changing (consistent with m3m → 4/m). Coupling of the two order parameters QI, and QII gives rise to the intermediate 4/mmm tetragonal phase.
Our results confirm the existence of an I4 1/a→I4 1/acd transition, but the non-disappearance of the 200 reflexion at high temperatures implies that the expected transition from I41/acd to Ia3d (cubic) symmetry does not occur. We attribute this to a residual strain field conjugated to the order parameter, due to defects (with possible Al/Si order). Nevertheless, within our experimental resolution, the lattice becomes metrically cubic at 665° C.
Similar content being viewed by others
References
Brown IWM, Cardile CM, Mackenzie KJD, Ryan MJ, Meinhold RH (1987) Natural and synthetic leucites studied by solid state 29-Si NMR and 57-Fe Mössbauer spectroscopy. Phys Chem Minerals 15:78–83
Faust GT (1963) Phase transition in synthetic and natural leucite. Schweiz Mineral Petrogr Mitt 43:165–195
Grögel T, Boysen H, Frey F (1984) Neutron powder investigation of I41/a-Ia3d in leucite. Collected Abstracts of 13th Int. Congress of Crystallography C256-257
Hirao K, Soga N, Kunugi M (1976) Thermal expansion and structure of leucite-type compounds. J Phys Chem 80:1612–1616
Kosorukov AA, Nadal LG (1986) High-temperature x-ray diffraction of synthetic leucite, Rb[AlSi2O6], and pollucite. Sov Phys Crystallogr 31(2):148–151
Lange RA, Carmichael ISE, Stebbins JF (1986) Phase transitions in leucite (KAlSi2O6), orthorhombic KAlSiO4, and their iron analogues (KFeSi2O6, KFeSiO4). Am Mineral 71:937–945
Mazzi F, Galli E, Gottardi G (1976) The crystal structure of tetragonal leucite. Am Mineral 61:108–115
Murdoch JB, Stebbins JF, Carmichael ISE, Pines A (1988) A silicon-29 nuclear magnetic resonance study of silicon-aluminium ordering in leucite and analcite. Phys Chem Minerals 15:370–382
Palmer DC, Putnis A, Salje EKH (1988) Twinning in tetragonal leucite. Phys Chem Minerals 16:298–303
Peacor DR (1968) A high temperature single crystal diffractometer study of leucite, (K, Na)AlSi2O6. Z Kristallogr 127:213–224
Phillips BL, Kirkpatrick RJ, Putnis A (1989) Si, Al ordering in leucite by high-resolution 27-A1 MAS NMR spectroscopy. Phys Chem Minerals 16:591–598
Redfern SAT, Salje EKH (1987) Thermodynamics of plagioclase II: temperature evolution of the spontaneous strain at the \(I\bar 1 - P\bar 1\) phase transition in anorthite. Phys Chem Minerals 14:189–195
Sadanaga R, Ozawa T (1968) Thermal transition of leucite. Mineral J 5:321–333
Salje E, Kuscholke B, Wruck B, Kroll H (1985) Thermodynamics of sodium feldspar II: Experimental results and numerical calculations. Phys Chem Minerals 12:99–107
Salje E (1987) Thermodynamics of plagioclases I: Theory of the \(I\bar 1 - P\bar 1\) phase transition in anorthite and Ca-rich plagioclases. Phys Chem Minerals 14:181–188
Taylor D, Henderson CMB (1968) The thermal expansion of the leucite group of minerals. Am Mineral 53:1476–1489
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Palmer, D.C., Salje, E.K.H. & Schmahl, W.W. Phase transitions in leucite: X-ray diffraction studies. Phys Chem Minerals 16, 714–719 (1989). https://doi.org/10.1007/BF00223322
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00223322