Crystal structures, phase transitions and physical properties of new double perovskites as advanced energy materials

• Applicant: Dr. Asmaa Zaraq
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Mineralogy, Petrology and Geochemistry
• Term: from 2020 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 447570761

The present proposal aims to study double-perovskite compounds and their application as advanced energy materials. The main objectives are the synthesis of new compounds, the determination of their crystal structures and the corresponding physical properties as well as their phase-transition behavior at low and high temperatures. The synthesis of these substances will be based on different methods such as solid-state reaction, hydrothermal and coprecipitation to obtain fine particles of polycrystalline, nanoparticles or to prepare a single crystal. X-ray diffraction studies will indicate the structural evolution according to the temperature and chemical composition of the double perovskite. With respect to these two variables, these classes of double-perovskite materials exhibit a large series of structural phase transitions. In addition, double-perovskite materials present interesting transitions of the electronic and magnetic properties because of those effects. Double-perovskite materials with the general formulas A2BB'O6 and AA'BB'O6 show many functional properties such as ferroelectricity, ferromagnetism, multiferroicity, giant magnetoresistance, and even high-temperature superconductivity, these properties originate from the characteristics of the chemical elements present on sites A and B, where A and A' might be Ca or Sr, B is occupied by magnetic 3d transition metal ions and B' will be 4th and 5th rows transition metal ions [1, 2]. Alternating Current (AC) magnetic susceptibility measurements will be used to study magnetic phase transitions and spin dynamics with time. We will also study these transitions of physical properties by calculating lattice parameters, band gaps, and density of states using Density Functional Theory method (DFT method) (EDOS (Electronic Density Of States) for phonon dispersion and band gaps behavior, PDOS (Phonon Density Of States) for interpretation of modes in IR and Raman spectroscopy). This project will help to understand the physical properties of these materials and it will also cover the lacking theoretical data on crystal structures of these interesting compounds, to use them in energy-related technologies.

• DFG Programme: WBP Position