- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Pushing Boundaries: High Pressure, Supercritical Optical Floating Zone Materials Discovery
摘要： In this perspective review, we provide the rationale for utilizing supercritical fluids for solid state materials discovery in the context of recent advances in the field of high pressure synthesis. We discuss the importance of the transition from gas-like to solvent-like environments in which materials synthesis and crystallization is occurring, the appropriate conceptual frameworks for its impact on synthesis and directional solidification, and dispel popular myths. We provide an overview of materials that have been grown in single crystal form by the high pressure optical floating zone technique, report the first successful stable molten zone in an optical furnace at P = 300 bar, and show viability of the traveling solvent method even with high fluid pressures. Further, we report on some unexpected observations found in the highly dynamic synthesis environment of supercritical fluids, enabled by the ability to observe, in real time, materials behavior. Finally, we offer a perspective on the scientific domains opened by these new capabilities.
关键词： Single crystal growth,Materials discovery,Optical floating zone,High pressure synthesis,Supercritical fluids
更新于2025-09-23 15:19:57
-
High-Pressure Synthesis, Crystal Structure, Chemical Bonding, and Ferroelectricity of LiNbO <sub/>3</sub> -Type LiSbO <sub/>3</sub>
摘要： A polar LiNbO3 (LN)-type oxide LiSbO3 was synthesized by a high-temperature heat treatment under a pressure of 7.7 GPa and found to exhibit ferroelectricity. The crystal structural re?nement using the data of synchrotron powder X-ray di?raction and neutron di?raction and the electronic structure calculation of LN-type LiSbO3 suggest a covalent-bonding character between Sb and O. When comparing the distortion of BO6 in LN-type ABO3, the distortions of SbO6 in LiSbO3 and SnO6 in ZnSnO3, which included a B cation with a d10 electronic con?guration, were smaller than those of BO6 in LN-type oxides having the second-order Jahn?Teller active B cation, e.g., LiNbO3 and ZnTiO3. The temperature dependence of the lattice parameters, second harmonic generation, dielectric permittivity, and di?erential scanning calorimetry made it clear that a second-order ferroelectric?paraelectric phase transition occurs at a Curie temperature of Tc = 605 ± 10 K in LN-type LiSbO3. Further, ?rst-principles density functional theory calculation suggested that perovskite-type LiSbO3 is less stable than LN-type LiSbO3 under even high pressure, and the ambient phase of LiSbO3 directly transforms to LN-type LiSbO3 under high pressure. The phase stability of LN-type LiSbO3 and the polar and ferroelectric properties are rationalized by the covalent bonding of Sb?O and the relatively weak Coulomb repulsion between Li+ and Sb5+.
关键词： high-pressure synthesis,LiNbO3-type oxide,covalent bonding,ferroelectricity,second-order Jahn?Teller effect,LiSbO3
更新于2025-09-10 09:29:36
-
High pressure synthesis of A2NiO2Ag2Se2 (A = Sr, Ba) with a high spin Ni2+ in square planar coordination
摘要： Square-planar coordinate Ni2+ in oxides are exclusively limited to a low spin state (S = 0) owing to extensive crystal field splitting. Here we report layered oxychalcogenides A2NiIIO2Ag2Se2 (A = Sr, Ba) with the S = 1 NiO2 square lattice. The structural analysis revealed that the Ni2+ ion is under-bonded by a significant tensile strain from neighboring Ag2Se2 layers, leading to the reduction in crystal field splitting. Ba2NiO2Ag2Se2 exhibits a G-type spin order at 130 K, indicating fairly strong in-plane interactions. The high-pressure synthesis employed here possibly assists the expansion of NiO2 square lattice by taking the advantage of the difference in compressibility in oxide and selenide layers.
关键词： oxychalcogenide,spin state,high pressure synthesis,strain,square lattice
更新于2025-09-09 09:28:46