Hydrothermal crystal growth of the high-pressure phases of α-PbO2 and TiO2 II

• Published in: Journal of alloys and compounds 2004-09, Vol.377 (1-2), p.17-20
• Main Authors: Dyuzheva, T.I., Lityagina, L.M., Bendeliani, N.A.
• Format: Article
• Language: English
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2004.01.033

The beta modification of lead dioxide, which is metastable under normal condictions, crystallized with the tetragonal rutile structure type. The denser orthorhombic phase can be obtained under the action of shear stress by crushing beta-PbO2 to powder. The structural model of this phase deduced from powder diffraction data is well known as alpha-PbO2 structure type. In spite of the existence of a large number of phases with alpha-PbO2 structure type which are metastable under normal condictions, any information about single crystals and their structural determination is absent in the literature. Single crystals of high-pressure phases of alpha-PbO2 and TiO2 II were grown under hydrothermal conditions. Dark brown crystals of lead dioxide with a size of about 0.25 mm x 0.25 mm x 0.65 mm were obtained at p = 4 GPa and T = 300-600 C. Transparent, colorless crystals of titanium dioxide with a size of about 0.03 mm x 0.03 mm x 0.15 mm were grown at p = 9-9.5 GPa and T = 600-900 C. Crystal morphology is presented for both compounds.