SKM 2023 – wissenschaftliches Programm
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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 11: Crystal Structure Defects / Real Structure / Microstructure
KFM 11.7: Vortrag
Donnerstag, 30. März 2023, 16:15–16:35, POT 51
Local structure of titanite CaTiSiO5 — •Arkadiy Simonov — ETH Zürich, Zürich, Switzerland
Titanite, CaTiSiO5, is a multifunctional nesosilicate mineral which recently received attention as a material for building tunable capacitors and oscillators. Near 500K titanite shows a nonlinear dielectric response with positive dielectric tunability and thus its dielectric susceptibility can be efficiently controlled using a voltage bias, moreover capacitors made of this material have unusually low dielectric losses and thus high quality factor [1]. The origin of such a good performance is not currently understood, but one hypothesis is that it is related to an unusual locally antipolar disordered structure which is observed in titanite above 500K in the paraelectric A2/a phase.
In this work we present the analysis of the local structure of titanite in the A2/a phase. We use single crystal diffuse scattering as our probe and analyze it using a non-parametric method based on three dimensional difference pair distribution function (3D-ΔPDF) refinement. We show that despite the A2/a structure is on average paraelectric, locally it is antipolar. It shows Ti4+ displacements which have strong ferro correlations along the b direction and weak locally anti-ferro correlations in a and c directions. Such locally antipolar structure can provide a crossover path for the low temperature P21/a structure under applied electric field and thus explain the low dielectric losses observed in this material.
[1] Murata, T., Asaka, T., Hirose, S. (2021). J. Am. Cer. Soc. 104(11), 5794-5802.