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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 13: Focus Session: (Multi-)Ferroic States III

KFM 13.5: Talk

Wednesday, March 20, 2024, 11:10–11:30, EMH 225

Experimental evidence for the PJTE in alkali niobates — •Leif Carstensen and Wolfgang Donner — Technical University of Darmstadt, Germany

The electronic origin of antiferroelectricity is considered not fully understood by most of the scientific community. Sodium niobate evolves from a paraelectric cubic to an antiferroelectric orthorhombic structure via a series of phonon instabilities. A combination of Rietveld refinement and Maximum Entropy Method is performed to gain insight into the differences between ferroelectrics and antiferroelectrics with respect to their electron density. Using this technique, the electron density distributions of room temperature sodium niobate and potassium niobate have been calculated from powder diffraction experiments to study the extent to which the Pseudo-Jahn-Teller effect changes the electron distribution from the originally fully ionic bonding proposed for the cubic structures of these perovskites. This study delivers experimental results to back up the PJTE theory and proves that the Rietveld-MEM approach is not limited to large radiation facility data, making it much more commonly available.

Keywords: Antiferroelectricity; Pseudo-Jahn-Teller effect; Perovskite; Maximum Entropy Method; Electron Density