Pressure-induced amorphization of A-site-deficient double perovskite Ln1/3MO3 (Ln = Pr, Nd, M = Nb, Ta)
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High-pressure X-ray diffraction measurements have demonstrated that the cation-deficient perovskites Pr1/3NbO3, Pr1/3TaO3, Nd1/3NbO3, and Nd1/3TaO3 undergo irreversible pressure-induced amorphization (PIA). This occurs near 14.5 GPa for the niobates and 18.5 GPa for the tantalates. The unit cell volumes of the four oxides show an almost linear decrease as the pressure is increased. It is concluded that the PIA transition occurs at higher pressures in the tantalates due to the lower MO6 initial tilting at ambient conditions, which is associated with the larger atomic mass of the tantalum. The behavior of these oxides is compared to that of CaTiO3, and the role of both the weakening of the M–O–M π-bonding and the cation vacancies on the observed structural changes is discussed.
KeywordsPerovskite High pressure Pressure-induced amorphization
The authors acknowledge ANKA for granting beamtime at SUL-X. The research at ANKA received funding from the European Community’s Seventh Framework Programme under Grant Agreement No 226716 (ELISA) for proposal CM 68. This work was partially supported by the Australian Research Council.
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