Related Experiment Video
Updated: May 11, 2026
08:49
Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films
Published on: December 4, 2014
Redetermination of Nd2Ti2O7: a non-centrosymmetric structure with perovskite-type slabs
Nobuo Ishizawa1, Keisuke Ninomiya, Terutoshi Sakakura
1Advanced Ceramics Research Center, Nagoya Institute of Technology, Asahigaoka 10-6-29, Tajimi 507-0071, Japan.
Summary
Single crystals of dineodymium(III) dititanium(IV) hepta-oxide (Nd2Ti2O7) were synthesized. This compound exhibits perovskite-type structural motifs with net polarization along the c-axis due to ion displacement.
Area of Science:
- Solid-state chemistry
- Crystallography
- Materials science
Background:
- Dineodymium(III) dititanium(IV) hepta-oxide (Nd2Ti2O7) is a material with potential applications in electronic devices.
- Understanding its crystal structure is crucial for optimizing its properties.
- Previous structural determinations exist but may not capture all details.
Purpose of the Study:
- To synthesize single crystals of Nd2Ti2O7 using the flux method.
- To determine the crystal structure and investigate the structural motifs.
- To analyze the atomic displacements and their relation to net polarization.
Main Methods:
- Flux method for single crystal synthesis.
- X-ray diffraction for crystal structure determination.
- Analysis of coordination polyhedra and atomic positions.
Main Results:
- Single crystals of Nd2Ti2O7 were successfully synthesized.
- The compound crystallizes with perovskite-type structural motifs.
- Perovskite-type slabs are stacked parallel to (010), with a thickness of four corner-sharing TiO6 octahedra.
- Neodymium (Nd) and titanium (Ti) ions are displaced from their ideal positions, leading to net polarization along the c-axis.
- The crystals were found to be twinned, exhibiting a halved monoclinic unit cell compared to prior studies.
Conclusions:
- The flux method is effective for synthesizing Nd2Ti2O7 single crystals.
- The detailed crystal structure reveals ion displacements responsible for polarization.
- The findings refine the understanding of Nd2Ti2O7's structure and properties, potentially impacting materials science applications.
Related Concept Videos
02:42Ionic Crystal Structures
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...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
02:57Coordination Number and Geometry
For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar.
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
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...
01:29Determination of Crystal Structures
In the late 1800s, the revelation that light extended beyond visible wavelengths led to the discovery of X-rays by Wilhelm Roentgen. Recognized as high-energy electromagnetic radiation with short wavelengths, X-rays prompted exploration into their interaction with crystals. Max von Laue proposed in 1912 that the periodic arrangement of atoms, ions, or molecules in crystals would cause them to diffract X-rays, a hypothesis confirmed through experiments with copper sulfate and zinc sulfide...