Dresden 2003 – wissenschaftliches Programm

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DF: Dielektrische Festkörper

DF 6: Keramiken, Gradientenwerkstoffe und Relaxoren

DF 6.8: Vortrag

Mittwoch, 26. März 2003, 17:10–17:30, HSZ/403

Effect of high pressure on relaxor ferroelectrics — •Jens Kreisel¹, Pierre Bouvier², Brahim Dkhil³, Bacem Chaabane^1,2, Mike Glazer⁴, and Pamela Thomas⁵ — ¹Lab. Materiaux et Genie Physique, ENS de Physique de Grenoble — ²LEPMI, ENS Electrochimie Grenoble — ³SPMS, Ecole Centrale Paris — ⁴Clarendon Laboratory, Oxford University — ⁵Physics Department, Warwick University

Relaxor ferroelectrics (relaxors) form a special class of ferroelectric materials of which the understanding remains a challenging problem. From an application point of view, relaxor-based materials have been reported to exhibit near structural phase boundaries outstanding electromechanical properties, which point to a potential revolution in electromechanical transduction for a large range of applications. Here we present first-time high-pressure investigations by Raman spectroscopy, diffraction and diffuse scattering of PbMg1/3Nb2/3O3 (PMN) and Na1/2Bi1/2TiO3 (NBT), considered as model relaxor materials. We show that an external pressure of several GPa (as can be met in thin films) alters fundamentally the structural and polar properties in relaxor ferroelectrics. The observed pressure-dependent Raman spectra are very unusual, pointing to a new relaxor-specific spectral signature. Furthermore, the observed total suppression of the relaxor-characteristic X-ray diffuse scattering with pressure points to a pressure-induced crossover from short-to-long-range order. The gradually decrease of the diffuse scattering can be understood in terms of a pressure-induced reduction of the mechanical strain between the non-polar average structure and the polar nano-regions.