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5-4
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Measurement of the instantaneous speckles reflected from a ferroelectric single crystal of BaTiO3
The reflected photons from the domain structures, illuminated by a spatially filtered X-ray beam from a slit, interfere with each other and give rise to speckle patterns, which are detected by an X-ray detector. For BaTiO3 at room temperature, there exist some micron-order domains that change with temperature. Different domain structures will give different speckle patterns. Compared to that at room temperature, the speckle pattern near the Curie temperature Tc (the critical temperature where ferroelectricity disappears, 122 degree Celsius here) looks narrower, indicating that the domain size has become larger. These patterns also show that the domain structure disappears above the Curie temperature (130 degree Celsius).
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