Related Experiment Video
Updated: May 5, 2026
08:43
Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles
Published on: October 27, 2018
17.7K
Structural disorder in AMoO4 (A = Ca, Sr, Ba) scheelite nanocrystals
Federico A Rabuffetti1, Sean P Culver, Leopoldo Suescun
1Department of Chemistry, University of Southern California , Los Angeles, California 90089, United States.
Inorganic Chemistry
|November 26, 2013
Summary
Investigating AMoO4 nanocrystals reveals that the Mo-O bond distance is composition-independent at the local level. Orientational disorder of tetrahedra explains discrepancies between average and local crystal structure models.
Area of Science:
- Materials Science
- Crystallography
- Nanotechnology
Background:
- Scheelite AMoO4 (A = Ca, Sr, Ba) nanocrystals are technologically relevant materials.
- Understanding their crystal structure at the nanoscale is crucial for material property prediction.
Purpose of the Study:
- To investigate the crystal structure of sub-15 nm AMoO4 nanocrystals.
- To reconcile discrepancies between average and local structural models derived from diffraction data.
Main Methods:
- Synchrotron X-ray diffraction data analyzed using a dual-space approach.
- Combined Rietveld and Pair Distribution Function (PDF) analysis.
Main Results:
- Rietveld analysis indicated an anomalous Mo-O bond contraction with chemical substitution, contradicting known material properties.
- PDF analysis revealed a negligible Mo-O bond contraction, independent of chemical composition.
- Discrepancies were attributed to static orientational disorder of MoO4 tetrahedra.
Conclusions:
- The structural integrity of MoO4 tetrahedra is maintained across different compositions.
- Static orientational disorder of MoO4 tetrahedra explains the observed structural behavior in AMoO4 nanocrystals.
- PDF analysis provides a more accurate local structural picture than Rietveld analysis for these materials.
Related Concept Videos
02:42Ionic Crystal Structures
18.1K
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
18.1K
01:29Imperfections in Crystal Structure: Non-Stoichiometric Defects
117
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...
117
01:26Imperfections in Crystal Structure: Stoichiometric Point Defects
147
Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...
147
01:25Imperfections in Crystal Structure: Point, Line and Plane Defects
153
A perfect crystal, in theory, has a uniform structure with the same unit cell and lattice points throughout. However, any deviation from this periodic arrangement is known as an imperfection or defect. These defects can be categorized into three types: point, line, and plane defects.Point defects occur when there is a deviation from the ideal due to missing atoms, displaced atoms, or additional atoms. These imperfections might occur due to imperfect packing during crystallization or because of...
153
02:37Metallic Solids
16.4K
Metallic solids such as crystals of copper, aluminum, and iron are formed by metal atoms. The structure of metallic crystals is often described as a uniform distribution of atomic nuclei within a “sea” of delocalized electrons. The atoms within such a metallic solid are held together by a unique force known as metallic bonding that gives rise to many useful and varied bulk properties.
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and...
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and...
16.4K
02:22Structures of Solids
18.0K
Solids in which the atoms, ions, or molecules are arranged in a definite repeating pattern are known as crystalline solids. Metals and ionic compounds typically form ordered, crystalline solids. A crystalline solid has a precise melting temperature because each atom or molecule of the same type is held in place with the same forces or energy. Amorphous solids or non-crystalline solids (or, sometimes, glasses) which lack an ordered internal structure and are randomly arranged. Substances that...
18.0K