Memory and Perfection in Ferroelastic Inclusion Compounds

• Published in: Crystal growth & design Vol. 5; no. 6; pp. 2100 - 2116
• Main Authors: Hollingsworth, Mark D, Peterson, Matthew L, Rush, Jeremy R, Brown, Michael E, Abel, Mark J, Black, Alexis A, Dudley, Michael, Raghothamachar, Balaji, Werner-Zwanziger, Ulrike, Still, Ezra J, Vanecko, John A
• Format: Journal Article
• Language: English
• Published: Washington,DC American Chemical Society 01.11.2005
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Elasticity, elastic constants; Exact sciences and technology; Ferroelectricity and antiferroelectricity; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Materials science; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Methods of crystal growth; physics of crystal growth; Nuclear magnetic resonance and relaxation; Physics; Switching phenomena; Impurity density; Hydrogen; White radiation; Irreversible processes; Urea; Ferroelastic materials; Impurities; Superelasticity; Anisotropy; Inclusion compounds; Ferroelectric switching; Ureas; Memory effect; Synchrotron radiation; X-ray topography
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg050347j

In a series of ferroelastic urea inclusion compounds (UICs), in which domain reorientation occurs upon application of an external anisotropic force, introduction of a relaxive impurity that disrupts a specific hydrogen-bonding network transforms a plastic (irreversible) domain-switching process into one that exhibits a striking memory effect and “rubber-like behavior”, a form of pseudoelasticity. As expected for a highly cooperative process, the ferroelastic response to the impurity concentration exhibits a critical threshold. Through synchrotron white-beam X-ray topography (SWBXT) of crystals under stress, videomicroscopy of spontaneous repair during crystal growth, acoustomechanical relaxation of daughter domains, kinetic measurements of spontaneous domain reversion, and solid-state 2H NMR of labeled guests, this work shows how relaxive impurities lower the barrier to domain switching and how differences in perfection between mother and daughter domains provide the driving force for the memory effects. Although the interfacial effects implicated here are different from the volume effects that operate in certain shape memory materials, the twinning and defect phenomena responsible for the rubber-like behavior and memory effects should be generally applicable to domain switching in ferroelastic and ferroelectric crystals and to other solid-state processes.