Abstract
We study the hydrostatic pressure dependence of the Y123 lattice by synchrotron angle-dispersive powder diffraction up to 12.7 GPa in order to detect any lattice instabilities or phase separation observed by Raman measurements. In the pressure range (3.7 GPa<p<10 GPa) mainly the c-axis (and to a smaller extend the a-, b-axis) undergoes a clear deviation from the expected equation of state. Upon the pressure release the data follow the anticipated dependence showing a strong hysteresis. At the pressure of ∼3.7 GPa new peaks appear in the diffraction patterns, which can be attributed to another apparently coherent phase that exhibits enhanced disorder and texture effects. The intensity of the new peaks decreases with increasing pressure and upon pressure release they disappear for p<3.9 GPa. The in-plane Cu-Opl bonds, the Cu2-Cu1 distance and the fractional coordinate of Ba atom along the c-axis of the Y123 phase show modifications at characteristic pressures in complete agreement with the Raman measurements under pressure, strongly indicating a pressure-induced lattice instability and phase separation.