Single Crystal Of Sr0 Research Articles

Detection of Negative Thermal Expansion in a Single Crystal of Sr0.75Ba0.25Nb6O2 Relaxor Ferroelectric by X-Ray Diffraction Analysis

The atomic structure of a single crystal of Sr0.75Ba0.25Nb6O2 representing a relaxor ferroelectric is determined from X-ray diffraction data. At nine temperatures within a range of 93–480 K, 12 experiments are performed. The experimental facilities (area detector, goniometer, and sample cooling system) are calibrated. The region of negative thermal expansion with respect to the unit-cell parameter с is revealed at 272–324 K. In the same region, an electrical resistance anomaly is observed. It is found that the structural parameters have a singularity at 296 K, in particular, an unusual thermal motion of atoms is observed. This correlates with a kink in the resistance–temperature curve at 297.5 K. The obtained results and analysis of published data indicate that, near room temperature, several physical properties of Sr0.75Ba0.25Nb6O2 relaxor at once have singularities, which can be explained by the revealed lattice instability.

Anisotropic thermal expansion of strontium barium niobate

Strontium barium niobate is a tungsten-bronze ferroelectric crystal having a tetragonal unit cell. Low-temperature x-ray diffraction studies were performed on a single crystal of Sr0.75Ba0.25Nb2O6 to determine the thermal expansivity along the a- and c-axes. Negative thermal expansion was observed along the c direction while a positive thermal expansion was measured along the a axis. The anisotropic thermal expansion behavior is explained as arising due to the geometry of the crystal structure.

Investigation of the Thermal Hysteresis at the Phase Transition of Relaxor Ferroelectric Sr0.61Ba0.39(NbO3)2

Measurements of birefringence and dielectric constant in single crystals of Sr0.61Ba0.39(NbO3)2, evidence a thermal hysteresis (Δ T ≅ 5°C) related to the discontinuous first order ferroelectric transition. The experimental results are analyzed in the light of the effective field approach and compared with the parameters characteristics of a classic perovskite like BaTiO3.

Neutron diffraction studies of phase transition effects on a single crystal of Sr0.7Ba0.3Nb206

Abstract On the relaxor-type ferroelectric Sr0.7Ba0.3Nb206 (SBN-70) phase transition (PT) phenomena are studied between room temperature (RT) and 773 K using the time-of-flight (TOF) diffraction technique. At RT the influence of an external electric field on the PT is investigated. Besides the diffused ferroelectric PT another transition is indicated above 500 K.