On the Structural and Magnetic Properties of B-site Ordered Double Perovkites

Taneli Tiittanen

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

Perovskites are one of the compound families that can be tailored to perform multiple scientifically and also technologically exciting and essential tasks. At the very early stage of perovskite history, right at the same time as the structure was solved, the first application possibility was found in electronics. The introduction of BaTiO3 as a dielectric material greatly enhanced the performance of ceramic capacitors of the time. Not to a surprise, it is still used in the very same application, some 80 years after the discovery. Since then, perovskites have found their way to widespread and emerging applications, from capacitors to solid oxide fuel cells, piezoelectric transducers and actuators to second harmonic generators in lasers and to spintronics, not to forget phenomena purely of academic interest. This thesis aims to bring its portion to the pool of scientific data to be used to expand the knowledge of the perovskite structure and properties within. New double perovskites with tuned crystal structures were synthesised by introducing a set of elements from the Periodic Table and by applying a variety of solid-state chemistry synthesis methods. Not only synthesis and characterisation, but also multivariate analysis and prediction of new compounds were performed. The time and effort required to design, make and characterise each perovskite may be enhanced by utilising multivariate data analysis of the existing data. The main target of the multivariate data analysis was to find new ferromagnetic B-site ordered double perovskite candidates. The proposed candidate compound should have ferromagnetic transition temperature within a reasonable temperature range in order to have an application without extensive or impractical effort to reach the operating temperature. Samples of two non-perovskite systems, (Sr,Ba)2FeSbO6 and Y2CuTiO6, were transformed into a variety of double perovskites with different crystal structures by applying synthesis techniques ranging from ambient pressure cation substitution to high-pressure high-temperature treatment. The SIMCA multivariate data analysis provided insight into ferromagnetic B-site ordered double perovskites. Agreement between the measured and predicted ferromagnetic transition temperatures were found as a result of the chosen multivariate analysis methods. Some non-perovskite compounds, previously synthesized but uncharacterised double perovskites and completely new stoichiometries were proposed as new ferromagnetic double perovskite candidates.
Translated title of the contributionOn the Structural and Magnetic Properties of B-site Ordered Double Perovkites
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Karppinen, Maarit, Supervising Professor
Publisher
Print ISBNs978-952-64-0037-2
Electronic ISBNs978-952-64-0038-9
Publication statusPublished - 2020
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • solid state chemistry
  • perovkites
  • magnetic properties

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