Polar Growth and Directional Adsorption of Large AlPO₄-5 Crystals Determined by Scanning Pyroelectric Microscopy

Abstract

Scanning pyroelectric microscopy on large crystals reveals the three-dimensional polarization distribution in AlPO 4 -5 crystals. AlPO 4 -5 probably grows in such a way that one particular absolute configuration is formed. In general twinned crystals are formed. The twin domains exhibit an opposite polarization. A single domain is found when crystals are grown from a substrate. In some cases the crystals show a more complex domain structure, which can be attributed to specific growth conditions. From the polarization distribution 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 AlPO 4 -5 crystals and earlier observed preferential orientation of this guest molecule in the host structure.

Internal Transport Resistances and their Influence on Diffusion in Zeolites as Traced by Microscopic Measuring Techniques

“…Intergrowth effects similar to those shown in Fig. 1(c) were frequently observed in other AFI-type crystals synthesized in solution (Girnus et al, 1994;Klap et al, 1999Klap et al, , 2000. For some of these crystals it was shown that only the internal crystal components, which resemble geometrically the semi-pyramids in Fig.…”

Insights into Structure Direction of Microporous Aluminophosphates: Competition between Organic Molecules and Water

“…Klap et al have shown in a series of papers [24][25][26] that the Al À O À P vector (of the T À O À T bonds parallel to c) always points in the same direction (in fact, AFI crystal growth only takes place in that direction), thus giving a permanent polarisation to the crystal along the c direction. This macroscopic polarisation may cause the alignment of the water molecules in the 6-MR channels.…”

Intergrowth Structure of Zeolite Crystals as Determined by Optical and Fluorescence Microscopy of the Template‐Removal Process

“…The observed commonality is in line with the assumption that the synthesis starts from rapid growth along one direction (usually crystallographic c axis), resulting in a dumbbell-shaped crystal, observed at the early stages of the synthesis. [26] The gap around the center of the crystal is subsequently filled up to form a regular shape. It was proposed that a secondary nucleation process occurs at the interface between the central and outward structures, making the boundary between them defect-rich.…”