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Pressure driven structural phase transition in EuTaO4: experimental and first principles investigations
Saheli Banerjee1, Alka B Garg1,2, Himanshu K Poswal1,2
1High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Center, Mumbai 400085, India.
Summary
Europium orthotantalate (EuTaO4) undergoes a reversible phase transition near 17 GPa, confirmed by structural and vibrational studies. This transition involves a change in tantalum coordination, impacting its bulk modulus.
Area of Science:
- Materials Science
- Solid-State Chemistry
- High-Pressure Physics
Background:
- Rare earth orthotantalates are technologically important materials.
- Europium orthotantalate (EuTaO4) exhibits a monoclinic M'-type fergusonite phase (P2/c).
Purpose of the Study:
- To synthesize and characterize EuTaO4.
- To investigate its structural and vibrational properties under high pressure (HP).
- To determine the phase transition behavior and mechanical properties of EuTaO4.
Main Methods:
- Solid-state reaction for synthesis.
- Synchrotron-based X-ray powder diffraction for structural analysis.
- Raman spectroscopy for vibrational properties.
- High-pressure investigations up to 17 GPa.
- First-principles density functional theory calculations.
Main Results:
- Single-phase polycrystalline EuTaO4 was synthesized.
- An isostructural, first-order, reversible phase transition was observed near 17 GPa.
- Bulk moduli were determined for both low-pressure (136.0(3) GPa) and high-pressure (162.8(21) GPa) phases.
- The high-pressure phase shows an increased coordination number for tantalum (Ta) from 6 to 8.
- Computational methods corroborated the experimental findings of the phase transition and coordination change.
Conclusions:
- EuTaO4 exhibits a pressure-induced isostructural phase transition.
- The transition significantly alters the material's mechanical properties, indicated by the change in bulk modulus.
- The study provides crucial insights into the high-pressure behavior of rare earth orthotantalates.
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