MS16-P15 Assessment of Pyroelectricity in Polar Oxides from Atomic DisplacementsThe phenomenon of pyroelectricity is known since 2000 years and describes the temperature dependency of the spontaneous polarization in non-centrosymmetric crystals. The origin is based on displacements of the atomic positions induced by temperature variations. These structural changes are measurable with common structural analysis methods, e.g. single crystal X-ray diffraction (XRD). However, in addition electron density redistributions play a crucial role.
This work shows an approach how to use measurable structural changes in combination with electronic structure modeling to determine pyroelectric coefficients of materials. Atomic displacements have been determined with XRD for the crystal structures of the pyroelectric standards and well-known material systems lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) in a temperature range from 80 K to 400 K. As a result, the spontaneous polarization and the pyroelectric coefficient have been calculated and show a high comparability with theoretical and experimental data. Furthermore, the newly developed Resonant X-ray Diffraction method REXSuppress [Richter2018] provides increased sensitivity for very small displacements of the atoms. Hereby, destructive interference of the intensity at specific Bragg reflections is used to detect structural deviations at picometer accuracy. This is particularly important for tiny structural changes, as shown for the recently discovered pyroelectric migration-induced field-stabilized polar (MFP) phase in normally non-polar cubic strontium titanate (SrTiO3) [Hanzig2013, Hanzig2015].
This work may be of wide interest for the pyroelectric community, presenting an alternative approach to determine pyroelectric properties from structural data and for the characterization of structural and physical properties of new materials or phases.References:
[Richter2018] C. Richter et al. (2018), Nat. Commun. 9(1) 178
[Hanzig2013] J. Hanzig et al. (2013), Phys. Rev. B 88 2 024104
[Hanzig2015] J. Hanzig et al. (2015), New J. Phys. 17 2 023036
Keywords: atomic displacement, pyroelectricty, structure-property-relation