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Phase transition in a KPb |
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| Authors: | S. V. Mel’nikova L. I. Isaenko V. M. Pashkov I. V. Pevnev |
| Affiliation: | (1) Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russia;(2) Institute of Mineralogy and Petrography, Siberian Division, Russian Academy of Sciences, Universitetskii pr. 3, Novosibirsk, 630058, Russia |
| Abstract: | Crystals of the KPb2Br5compound are investigated using polarized light microscopy and calorimetry. The birefringence and the angle of rotation of the optical indicatrix are measured in the temperature range 270–620 K. It is found that the KPb2Br5 crystal undergoes a first-order ferroelastic phase transition at temperatures T0↑ = 519.5 K and T0↓ = 518.5 K with a change in the enthalpy ΔH = 1300 ± 200 J/mol. This transition is accompanied by both twinning and the symmetry change mmm ? P21/c. It is revealed that the angle of rotation of the optical indicatrix exhibits an unusual behavior under variations in the temperature due to a strong temperature dependence of the birefringence. |
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