Related Experiment Video
Updated: Jun 23, 2026
11:07
Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties
Published on: August 15, 2015
Phase transformations in Sr0.8Ba0.2CoO2.5 brownmillerite: correlation between structure and transport properties
C de la Calle1, J A Alonso, A Aguadero
1Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain.
Dalton Transactions (Cambridge, England : 2003)
|May 20, 2009
Summary
This study details the structural and transport properties of an oxygen-defective perovskite oxide, revealing new phases and correlating conductivity with structural changes for potential applications.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Crystallography
Background:
- Oxygen-defective perovskite oxides are crucial for various applications.
- Understanding their structural evolution and transport properties is key to material design.
Purpose of the Study:
- To synthesize and characterize an oxygen-defective perovskite oxide.
- To correlate its structural features with physico-chemical properties, particularly electrical conductivity.
- To identify and analyze novel structural phases and transitions.
Main Methods:
- Soft-chemistry synthesis followed by liquid nitrogen quenching.
- Temperature-dependent X-ray powder diffraction (XRPD) and neutron powder diffraction (NPD).
- Thermal analysis, electrical conductivity, and thermal expansion measurements.
Main Results:
- A new intermediate phase with an orthorhombic brownmillerite-like structure (Ibm2) stable up to 350°C was identified.
- This phase transforms to a Pnma structure upon oxygen intake, then irreversibly to a hexagonal 'H' phase at 653°C.
- A cubic perovskite phase ('C') formed above 920°C exhibits metallic conductivity and significant oxygen mobility.
Conclusions:
- The study elucidates the complex phase behavior of the oxygen-defective perovskite oxide.
- Structural transitions, including oxygen insertion and polymorph changes, directly impact electrical conductivity.
- The cubic perovskite phase shows promising mixed conductor behavior with high conductivity.
Related Concept Videos
02:54Molecular and Ionic Solids
Crystalline solids are divided into four types: molecular, ionic, metallic, and covalent network based on the type of constituent units and their interparticle interactions.
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
Molecular Solids
Molecular crystalline solids, such as ice, sucrose (table sugar), and iodine, are solids that are composed of neutral molecules as their constituent units. These molecules are held together by weak intermolecular forces such as London dispersion forces, dipole-dipole interactions, or hydrogen bonds, which...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
01:29Imperfections in Crystal Structure: Non-Stoichiometric Defects
Non-stoichiometric defects refer to a type of defect in the crystal structure of a compound where the ratio of its constituent elements deviates from the ideal stoichiometric ratio. There are two main types of non-stoichiometric defects: metal excess defects and metal deficiency defects.Metal excess defects occur when there is a slight surplus of metal ions than what is required by the stoichiometric ratio of the compound. For example, heating a sodium chloride crystal in sodium vapor results...
01:28Phase Diagrams of Ternary Systems
Consider a ternary system, which is composed of three components: water (W), ethanoic acid (E), and trichloromethane (T). Here, Ethanoic acid (E) is fully miscible with both water (W) and trichloromethane (T), meaning it can mix entirely with either of them. However, water and trichloromethane have partial miscibility, meaning they can only mix to a certain extent, beyond which two separate phases will form.The phase diagram of a ternary system is represented as an equilateral triangle, where...
02:58Properties of Transition Metals
Transition metals are defined as those elements that have partially filled d orbitals. As shown in Figure 1, the d-block elements in groups 3–12 are transition elements. The f-block elements, also called inner transition metals (the lanthanides and actinides), also meet this criterion because the d orbital is partially occupied before the f orbitals.
01:31Ferromagnetism
Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...