High-pressure phase transformations in NdVO4 under hydrostatic, conditions: a structural powder x-ray diffraction
T Marqueño1, V Monteseguro1, F Cova2
1Departament de Física Aplicada-ICMUV, Universitat de València, Dr. Moliner 50, 46100 Burjassot, Spain.
Summary
High-pressure experiments reveal new phase transitions in neodymium orthovanadate (NdVO4). This study details a novel zircon-to-scheelite transition and a subsequent transformation to a fergusonite-type structure under quasi-hydrostatic conditions.
Area of Science:
- Materials Science
- Solid State Chemistry
- Mineral Physics
Background:
- Neodymium orthovanadate (NdVO4) crystallizes in the zircon-type structure.
- Understanding the high-pressure behavior of rare-earth orthovanadates is crucial for materials science.
- Previous studies on similar compounds were often conducted under non-hydrostatic conditions, potentially influencing observed phase transitions.
Purpose of the Study:
- To investigate the high-pressure structural behavior of zircon-type NdVO4 under quasi-hydrostatic conditions.
- To identify and characterize phase transitions occurring in NdVO4 at room temperature.
- To compare the high-pressure behavior of NdVO4 with other rare-earth orthovanadates.
Main Methods:
- Angle dispersive powder X-ray diffraction was employed.
- Experiments were conducted at room temperature under quasi-hydrostatic pressures up to 24.5 GPa.
- Data analysis focused on structural changes and compressibility.
Main Results:
- NdVO4 undergoes two distinct phase transitions at 6.4 GPa and 19.9 GPa.
- The first transition (6.4 GPa) is a novel zircon-to-scheelite-type phase transition, contradicting prior non-hydrostatic studies.
- The second transition (19.9 GPa) involves a transformation to a fergusonite-type structure, a monoclinic distortion of the scheelite-type.
Conclusions:
- Quasi-hydrostatic conditions reveal new high-pressure polymorphs in NdVO4.
- The role of non-hydrostatic stresses is critical in understanding the structural behavior of rare-earth orthovanadates.
- The compressibility and axial anisotropy of different NdVO4 polymorphs were determined.
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