Confusion over the description of the quartz structure yet again
Journal of Applied Crystallography International Union of Crystallography 51 (2018) 915-918
Abstract:
In a recent paper [Huang, Gog, Kim, Kasman, Said, Casa, Wieczorek, Hönnicke and Assoufid (2018). J. Appl. Cryst. 51, 140–147], a description of the structure of quartz was given that is incorrect. There is a long history of such errors in publications describing the quartz structure. This was fully and correctly discussed in 1978 [Donnay and Le Page (1978). Acta Cryst. A34, 584–594], and yet these errors still persist. In the present paper the description by Huang et al. is corrected and the seminal work of Donnay and Le Page revisited.Crystallographic and optical study of LiNb1 - xTaxO3.
Acta crystallographica Section B, Structural science, crystal engineering and materials 73:Pt 3 (2017) 498-506
Abstract:
Powders of lithium niobate-tantalate across the full compositional range have been made and crystals grown using a lithium vanadate flux growth technique. The Li-content of a lithium tantalate crystal has been determined using the zero-birefringence temperature and Curie measurements, confirming the Li content is between that of congruent and stoichiometric crystals. X-ray diffraction measurements show the Nb/Ta displacement and octahedral tilt both decrease as the Ta content is increased. This also results in a decrease in the lattice parameters from lithium niobate to lithium tantalate. Birefringence measurements on the crystals as a function of temperature have been used to determine the point that the crystals become zero-birefringent, and by comparison with the structural studies have confirmed that it is not related to a phase transition and the structures remain polar through the zero-birefringence points.Crystallographic and optical study of PbHfO3 crystals.
Journal of applied crystallography 50:Pt 2 (2017) 378-384
Abstract:
The symmetry of the intermediate high-temperature phase of PbHfO3 has been determined unambiguously to be orthorhombic using a combination of high-resolution X-ray diffraction and birefringence imaging microscopy measurements of crystal plates. While lattice parameter measurements as a function of temperature in the intermediate phase are consistent with either orthorhombic or tetragonal symmetry, domain orientations observed in birefringence imaging microscopy measurements utilizing the Metripol system are only consistent with orthorhombic symmetry with the unit cell in the rhombic orientation of the pseudocubic unit cell.Relationship between the structure and optical properties of lithium tantalate at the zero-birefringence point
JOURNAL OF APPLIED PHYSICS 121:2 (2017)
FOURIER2D and FOURIER3D : programs to demonstrate Fourier synthesis in crystallography
Journal of Applied Crystallography International Union of Crystallography 49:6 (2016) 2276-2278