Regensburg 2025 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 1: (Multi)ferroic States: From Fundamentals to Applications (I)

KFM 1.4: Talk

Monday, March 17, 2025, 10:30–10:45, H9

Dielectric crossover and its structure-function relationship in pseudo Ruddlesden-Popper-type oxides — •Akitoshi Nakano and Hiroki Taniguchi — Nagoya University, Nagoya, Japan

A phase variation of a pseudo-Roddlesden-Popper-type ferroelectric oxide Li2Sr1-xCax(Nb1-xTax)2O7 is systematically investigated using dielectric measurements, and x-ray diffraction experiments. We find an exotic x-T phase diagram, including paraelectric Cmcm, antiferroelectric Pmcn, and in-plane antiferroelectric and out-of-plane ferroelectric P21cn phases. At low x, we observe large and divergent dielectric anomalies associated with phase transitions from Cmcm to P21cn, whereas it crosses over into a small kink as x increases. Structural analyses reveal an internal distortion, and the rotation of octahedra also strongly depends on x. These results demonstrate the great tunability of dielectric properties in layered perovskite-type oxides by tuning the chemical bonding state in the octahedron.

Keywords: ferroelectric; antiferroelectric; layered perovskite-type oxide; hybrid improper ferroelectricity; structural analysis