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Physicochemical parameters of ice crystals

Structural morphology

Monoclinic system, a0=0.547nm, b0=0.562nm, c0=0.782nm, β= 9011 '; Z=2. [AlF6] with slightly altered crystal structure

Composed of [NaF6] octahedron and [NaF12] cubic octahedron; Two types of octahedra are connected to form chains extending along the c-axis, and the chains are filled with other 2/3 of Na, with a coordination number of 12. The [AlF6] octahedron is located at the corner top and center of the crystal cell, while the [NaF6] octahedron is located at the center of the bottom surface and the middle of the vertical edge of the crystal cell. Four of the six [NaF12] are located on the crystal cell surface, while the other two are located in the crystal cell. At approximately 500 ℃ β- Cryolite is an equiaxed crystal system with Oh3-Fm3m; A0=0.795nm; Z=4. (NH4) 3AlF6 type structure, similar to potassium sodium cryolite structure. Due to the small radius of Na+distributed in the cubic octahedron, it cannot fill the space of the cubic octahedron. Therefore, under cooling conditions, the polyhedron tilts and transforms into a monoclinic crystal system.

Orthorhombic columnar crystal, C2h-2/m (L2PC). Common simplex: parallel double-sided a {100}, b {010}, c {001}, and diagonal columns s {111}. Due to the well-developed crystal planes of {001} and {010}, the crystal shape looks similar to a cube. Double crystals often follow (110). Usually in a dense block shape, sometimes in sheet or granular form.

Physical and chemical properties

Colorless, white, sometimes appearing as light gray, light brown, light red, or brick red. Stripe white. Glass luster to grease luster. Transparent to semi transparent. Without cleavage, with {001} and {110} cracks. Embrittlement. The fracture surface is uneven. Hardness 2-3. Relative density 2.95-3.1.

Under polarizer: colorless and transparent. Biaxial crystal (+), 2V=43?. Ng=1.3396, Nm=1.3389, Np=1.3385.

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Main uses of cryolite

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