Structural and thermal expansion studies of Li2ZrO3 were carried out by recording X‐ray powder diffraction patterns at five temperatures, 82, 198, 300, 423 and 573 K. The Rietveld refinement method was used for the analysis. There were large anisotropic changes in the lattice parameters as a function of temperature, slight changes in the fractional coordinates of the different atoms, and anisotropic changes in the interatomic distances between the different cations. The correlation of these anisotropies with the structure is considered.

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The crystal structure of the kaolinite mineral from Kalabsha, Aswan, Egypt, has been investigated with a two-step procedure of the X-ray powder pattern-fitting. The unit cell is found to be triclinic, PI, a = 5.1577 (15), 6 = 8.9417(23), c = 7.3967(40) A, a = 91.672(5)", = 104.860(2)" and y = 89.898(2)". The refinements of the non-hydrogen atomic positions showed a reliability factors R,, = 0.037 and RE = 0.0417. The average rotation angle in the tetrahedral layer in lo".

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Samples of amorphous Se, SSe40, SSe30, and SSe20 were synthesized and were then crystallized by annealing at 373 K for 5, 20, and 120 mins. The results showed that the changes in the structural and microstructural parameters for samples SSe40, and SSe30 are different from those of sample SSe20. These discrepancies are being discussed in terms of the peak shifts in both the amorphous and crystalline state, the percentage of sulfur compositional variations, and finally in terms of the probable site occupancy of the sulfur atoms in the selenium structure.