DOMAIN-STRUCTURE IN A FERROELASTIC PB3(PO4)2 CRYSTAL

The domain structure of the ferroelastic Pb3(PO4)2 crystals grown by the Czochralski method has been investigated by transmission electron microscopy and electron diffraction. We observed three kinds of domains and two different types of domain walls separating adjacent domains. One type of the measured wall represents the prominent (113BAR) and (113BAR) W planes. These observed planes are found to be in agreement with the theoretically deduced W-walls. Though the direction of the non-prominent W' plane at an angle of 17-degrees from the z-axis was also theoretically calculated, this W'-wall was not experimentally identified. Therefore, we have confirmed that the domain boundary in Pb3(PO4)2 is the prominent (113BAR) and (113BAR) W planes.