Ion Intercalation in Lanthanum Strontium Ferrite for Aqueous Electrochemical Energy Storage Devices

Quantifying Hydrogen Chemical Diffusivity in NdNiO3 Thin Films through Operando Multimodal Measurements

Nickelate oxides show unique properties that make them highly applicable in electrocatalysis, neuromorphic computing, and superconductors. Proton insertion, which effectively tunes their properties, is critical in advancing these applications. Its dynamics is governed by protonation kinetics, mainly controlled by hydrogen chemical diffusivity in nickelates. However, its precise quantification remains a significant knowledge gap, with reported values showing substantial discrepancies and a lack of comprehensive, rigorous methods. In this study, we propose a new quantitative approach that combines operando multimodal measurements. We provide the precise quantification of hydrogen chemical diffusivity in NdNiO3 (NNO), a prototypical nickelate, using rigorous kinetic modeling and cross-validation across multiple data dimensions. Our results reveal that proton mobility in NNO is inherently limited, challenging the assumption of its rapid transport in nickelates. This finding is critical for optimizing proton-based devices and paves the way for further understandings ion dynamics in correlated oxides.

Development of n-type ZnAlInO Semiconductor Materials for Thermoelectric Generators in Aerospace Applications

Thermoelectric conversion is a system that can convert heat energy originating from temperature difference into electrical energy. Although it has many advantages in terms of usage, research is required to acquire high-efficiency thermoelectric materials due to their low efficiency. Herein, Al- and In-doped ZnO semiconductor thermoelectric material is synthesized, produced, and examined for use in the production of thermoelectric generators that can be used in aviation applications. The synthesis of ZnAlIn powders is carried out by the sol-gel method. The xerogel is dried at 200 °C for 10 h, and the dried material is then calcined at 600 °C for 4 h in an atmospheric oven to obtain ZnAlIn material. The obtained powder is then compressed with a cold press to produce pellet samples. Pellet samples are sintered in an atmospheric furnace at 1350 °C for 36 h and are made ready for measurements. Comprehensive characterization and analysis of microstructural and structural properties are performed by Fourier transform infrared spectroscopy, differential thermal analysis-thermogravimetry, X-ray photoelectron spectroscopy, scanning electron microscopy, and X-ray diffraction methods. Seebeck coefficient and thermal capacity measurements are performed to determine thermoelectric properties. The results obtained from the study show that ceramic-based ZnAlIn semiconductor thermoelectric material has the required efficiency for thermoelectric generator production.

Iono-Optic Impedance Spectroscopy (I-OIS): A Model-Less Technique for In Situ Electrochemical Characterization of Mixed Ionic Electronic Conductors

Functional properties of mixed ionic electronic conductors (MIECs) can be radically modified by (de)insertion of mobile charged defects. A complete control of this dynamic behavior has multiple applications in a myriad of fields including advanced computing, data processing, sensing or energy conversion. However, the effect of different MIEC's state-of-charge is not fully understood yet and there is a lack of strategies for fully controlling the defect content in a material. In this work we present a model-less technique to characterize ionic defect concentration and ionic insertion kinetics in MIEC materials: Iono-Optic Impedance Spectroscopy (I-OIS). The proof of concept and advantages of I-OIS are demonstrated by studying the oxygen (de)insertion in thin films of hole-doped perovskite oxides. Ion migration into/out of the studied materials is achieved by the application of an electrochemical potential, achieving stable and reversible modification of its optical properties. By tracking the dynamic variation of optical properties depending on the gating conditions, I-OIS enables to extract electrochemical parameters involved in the electrochromic process. The results demonstrate the capability of the technique to effectively characterize the kinetics of single- and even multi-layer systems. The technique can be employed for studying underlying mechanisms of the response characteristics of MIEC-based devices.

Magnetoresistance (MR) properties of magnetic materials

In this review, the classification of magnetic materials exhibiting magnetoresistive properties is the focus of discussion because each material possesses different magnetic and electrical properties that influence the resulting magnetoresistance (MR) values. These properties depend on the structure and mechanism of the material. In this overview, the classification of magnetic materials with different structures is examined in several material groups, including the following: (1) perovskite structure (ABO3), (2) alloy, (3) spinel structure, and (4) Kagome magnet. This review summarizes the results of each material's properties based on experimental findings, and serves as a reference for studying the characteristics of each material.

Deeper mechanistic insights into epitaxial nickelate electrocatalysts for the oxygen evolution reaction

Mass production of green hydrogen via water electrolysis requires advancements in the performance of electrocatalysts, especially for the oxygen evolution reaction. In this feature article, we highlight how epitaxial nickelates act as model systems to identify atomic-level composition-structure-property-activity relationships, capture dynamic changes under operating conditions, and reveal reaction and failure mechanisms. These insights guide advanced electrocatalyst design with tailored functionality and superior performance. We conclude with an outlook for future developments via operando characterization and multilayer electrocatalyst design.