Our Speakers

20th May 2021 – Talk 10:

Local Structure of NaNbO3-based Antiferroelectric Ceramics Probed with NMR Spectroscopy

Dr. Pedro B. Groszewicz Delft University of Technology Netherlands Section Storage of Electrochemical Energy (SEE)

In this talk, I will overview the key aspects of solid-state nuclear magnetic resonance (NMR) spectroscopy of electroceramics,[1] with particular focus on NaNbO3-based antiferroelectric materials. This technique explores interactions between the probed nucleus and its close surroundings to provide insight into the structure at the atomic scale. An introduction to NMR spectroscopy tailored to the materials scientist will be presented, underlining the general aspects of the technique with respect to the local structure of perovskite oxides. Following this, three examples of the application of 23Na NMR to the study of NaNbO3-based antiferroelectrics will be discussed, highlighting the effect of grain size, electric field, and chemical substitution.

In the first example, the grain size-induced transition between the antiferroelectric P and ferroelectric Q polymorphs of NaNbO3 is analyzed with 23Na NMR. This technique enables one to quantify the relative amount of each phase and ultimately determine the critical grain size for the transition to the ferroelectric polymorph to occur.[2] This example is extended to the analysis of the field-induced transition between P and Q phases of NaNbO3 by means of ex situ 23Na NMR experiments.[3] In the last example, 23Na NMR is employed to investigate the local structure changes caused by the formation of NaNbO3-based solid solutions aimed at stabilizing the antiferroelectric polymorph. The consequences to the local structure disorder by the shared lattice occupation with different cations is analyzed. From this analysis it is concluded that a less distorted, albeit more disordered local environment for the Na1 site correlates with the stabilization of the AFE polymorph.[4]

[1] NMR spectroscopy of electroceramics – Applications to lead-free perovskite oxides, Pedro B. Groszewicz, Open Ceramics, 5, 100083 (2021).

[2] Grain-size-induced ferroelectricity in NaNbO3. J Koruza et al., Acta Materialia 126, 77-85, (2017).

[3] 23Na NMR Spectroscopic Quantification of the Antiferroelectric–Ferroelectric Phase Coexistence in Sodium Niobate, S Egert et al., The Journal of Physical Chemistry C 124 (43), 23852-2385 (2020).

[4] Design of Lead-Free Antiferroelectric (1 – x)NaNbO3–xSrSnO3 Compositions Guided by First-Principles Calculations, M.H. Zhang et al., Chemistry of Materials, 33, 1, 266–274 (2021)

Short Biography

Pedro B. Groszewicz is an Assistant Professor at the Delft University of Technology, Netherlands. His research focuses on electroceramic materials relevant for a CO2-neutral society, ranging from oxides for ionic conduction and high-power electronics, as well as alternative batteries based on metal fluorides, with a particular interest in studying structure-property relations.

He graduated in chemistry at the Universidade Federal do Paraná, Brazil, in 2010 and received his PhD degree in 2016 from the Technical University of Darmstadt, Germany. In this period, he specialized in the application of solid-state nuclear magnetic resonance (NMR) spectroscopy to study functional materials. During a postdoctoral stay at the University of Cambridge, UK, between 2019 and 2020, he was introduced to in situ capabilities of this technique and alternative battery chemistries, after which he moved to the Netherlands and joined the TU Delft.

About the FLAME-inars

The FLAME-inars are organized by the collaborative project FLAME at TU Darmstadt, in which electronic-structure-property relationships are being developed and exploited to realize novel lead-free antiferroelectric compounds. The seminars will gather experts in processing, characterization and theory to discuss materials and applications, bulk and thin films, fundamental properties, electronic structure & defects, and related aspects.