Morphology and Optical Properties of Precipitated Vivianite, Fe3(PO4)2·8H2O
Research output: Contribution to journal › Journal article › Research › peer-review
Crystals of vivianite, Fe3(PO4)2∙8H2O, belonging to the monoclinic prismatic class 2/m , are grown by precipitation from aqueous solution at temperatures from 25 to 56 °C. At 25 °C aggregates are dominating, but at 35 °C and above single crystals are more common, being tabular along {010} and most often with parallelogram outline; in a few cases twins are observed. The outline is distinct and consistent with published lattice parameters, but at low temperature the {010} faces are very rough as judged from interference colors seen in the polarizing microscope. Lateral faces belonging to the {110} form are visible on crystals grown at 45 and 56 °C, and the widths of their projections on {010} as measured with a micrometer eyepiece served for estimating crystal thickness, making use of the face angle from lattice parameters. Optical parameters are determined by a combination of three methods: 1) measurement of birefringence with an Ehringhaus 6λ compensator, 2) Kamb's method for the optic axis angle determined by the angle‐of‐flight method in conoscopic illumination, and 3) visual interferometry using a polarizing microscope incorporating a Mach–Zehnder interference device. Reasonably precise values of principal refractive indices in the expected range are found.
Original language | English |
---|---|
Article number | 1900226 |
Journal | Journal of Crystal Growth |
Volume | 55 |
Issue number | 6 |
Number of pages | 5 |
ISSN | 0022-0248 |
DOIs | |
Publication status | Published - 1 Jun 2020 |
ID: 243428194