VIBRATIONAL AND X-RAY MEASUREMENTS OF La2Ti2O7 UNDER HIGH PRESSURE CONDITION

Abstract

The present study focuses on investigating the impact of high-pressure conditions on the crystal structure and vibration spectra of the perovskite-like layered compound La2Ti2O7. To this end, X-ray diffraction and Raman spectroscopy techniques were employed to observe the behavior of the compound under pressure levels up to 30 GPa. The neutron diffraction at ambient pressure confirms that the structure of La2Ti2O7 is monoclinic P21. The results indicate that when the pressure attains 17.3 GPa, the original monoclinic phase of P21 symmetry undergoes a phase transition to the monoclinic phase of P2 symmetry. The observed pressure-induced phase transitions in La2Ti2O7 are associated with anomalous changes in both the unit cell parameters and the vibrational modes. Additionally, the study obtained the baric dependences of lattice parameters, unit cell volume and vibration frequencies, which were used to calculate the bulk modules for the initial and pressure-induced phases of La2Ti2O7.