Structural stability of orthorhombic DyScO3 under extreme conditions of pressure and temperature

Abstract

In the present work, the effect of elevated pressure and lowered temperature on the structural and vibrational stability of dysprosium scandate (${\mathrm{DyScO}}_{3}$) is studied via high-pressure synchrotron x-ray diffraction (HPXRD) and high-pressure (HP) and low-temperature Raman spectroscopy. A solid-state reaction route is employed to synthesize the material with a crystallite size of 92 nm, which at ambient conditions exhibits an orthorhombic phase with the space group $Pbnm$ (62). HPXRD results reveal excellent phase stability of the material, with the ratio of the polyhedral volumes and the compressibility for the ${\mathrm{DyO}}_{12}$ and ${\mathrm{ScO}}_{6}$ polyhedra to be around 4.26 and 1 for the entire applied pressure range of up to 40 GPa. Interestingly, the combination of HPXRD and HP Raman measurements signals a change in the preferred orientations in the crystalline structure with the increased pressure, while keeping the structure stable. The bulk modulus of the material is estimated to be 189.4 GPa from the HPXRD data and is further used to estimate the mode Gr\"uneisen parameter (\ensuremath{\gamma}) for various Raman modes. The behavior of phonon frequency with varying temperature is explained by considering the anharmonic effects, i.e., lattice expansion and perturbation in the Hamiltonian, with an increase in temperature. Furthermore, the implicit and explicit anharmonicity contributions were calculated to elucidate the phonon decay mechanisms. Our results offer valuable insights relating to the behavior of this intriguing class of materials under extreme conditions and lays the foundation for further exploration.