Polar growth and directional adsorption of large AlPO4-5 crystals determined by scanning pyroelectric microscopy

Scanning pyroelectric microscopy on large crystals reveals the three-dimens ional polarization distribution in AlPO4-5 crystals. AlPO4-5 probably grows in such a way that one particular absolute configuration is formed. In gen eral twinned crystals are formed. The twin domains exhibit an opposite pola rization. A single domain is found when crystals are grown from a substrate . In some cases the crystals show a more complex domain structure, which ca n be attributed to specific growth conditions. From the polarization distri bution the history of the crystal growth can be retrieved. A mechanism for the adsorption of p-nitroaniline molecules is proposed on the basis of the polarization distribution in AlPO4-5 crystals and earlier observed preferen tial orientation of this guest molecule in the host structure.