Phase transitions in the oxyfluoride (NH4)3NbOF6 |
| |
Authors: | S. V. Mel’nikova N. M. Laptash A. L. Zhogal’ |
| |
Affiliation: | (1) Kirensky Institute of Physics, Siberian Division, Russian Academy of Sciences, Akademgorodok, Krasnoyarsk, 660036, Russia;(2) Institute of Chemistry, Far East Division, Russian Academy of Sciences, pr. Stoletiya Vladivostoka 159, Vladivostok, 690022, Russia |
| |
Abstract: | (NH4)3NbOF6 single crystals were grown, polarization-optical studies were performed, and birefringence was measured over the temperature range 90–500 K. A sequence of first-order structural phase transitions was found at temperatures T 1↓ = 259.7 K and T 2↓ = 257.7 K with temperature hysteresis δT 1 = 0.9 K and δT 2 = 1.9 K. The transitions are accompanied by twinning and the following change in the crystal symmetry: cubic ? tetragonal ? monoclinic. Optical second harmonic generation is found to occur at room temperature, which indicates that the cubic phase is not centrosymmetric. It is assumed that the phase transitions are ferroelastic and ferroelectric in nature. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|