J. Phys. IV France
Volume 09, Numéro PR3, March 1999Proceedings of the 9th SolarPACES International Symposium on Solar Thermal Concentrating Technologies
|Page(s)||Pr3-463 - Pr3-466|
J. Phys. IV France 09 (1999) Pr3-463-Pr3-466
Plant for high-temperature X-ray analysis from 20° to 2700 °C in the air and crystal structure bias features detected in phase junction fieldsD.D. Gulamova
NPO Physics-Sun, 700084 Tashkent, Uzbekistan
The plant for high-temperature X-Ray analysis from 20° to 2700°C in the air imitates the mode of Big Solar Furnace (BSF) operation. The temperature is determined by object blackening. 10 KW Xenon lamp is the source of heating. Radiation flux heats the sample placed on the axis of goniometer. Crystal structure transformations of simple and complex oxides have been investigated (titanates of rare-earth compositions Ln2TiO5, Ln2Ti2O7, fluorite-similar solutions etc.) It is ascertained that phases occur in the regions of polymorphous transformations. Phase data describe a continious shift from low temperature to high temperature forms. As a rule, their crystallic structure is basic but distorted. Missing modifications have been disclosed for the compounds that in equilibrium conditions have no forms corresponding to theoretical sequence of transformations : monoc→ rhomb→ hexagon→ tetragon→ cube. Polymorphous forms of a number of oxides such as (rhombic for HfO2, ZrO2 etc.) have also been determined. The latter confirm that the realization of theoretical sequence of transformations with the symmetry improvement :(mon→ rhomb→ hexagon→ tetragon→ cube) depends on the internal conditions and their predetermined change can cause the stabilization of the structure desired.
© EDP Sciences 1999