Pressure-induced phase separation in the Y123 superconductor

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-O pl 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.

Pressure-induced lattice instabilities and superconductivity inYBa2Cu4O8and optimally dopedCalamiotou1, Gantis2, Siranidi3 et al. 2009Phys. Rev. BSelf Cite217190View full textAdd to dashboardCite

“…Previous structural studies under hydrostatic pressure up to 5 GPa (using a laboratory source) gave only some marginal evidence of a non-linear pressure dependence above 4 GPa [12]. We present here high quality synchrotron angle-dispersive powder diffraction data and micro-Raman spectra under hydrostatic pressure for the Pr123 (T c =0K) and Y124 (T c =80K) compounds in comparison with the corresponding ones for Y123 (T c =92K) [6]. The pressure region up to 13 GPa has been investigated with a pressure step of ≈ 0.5 GPa.…”

“…The pressure dependence of the a-, b-axis is shown in Fig.2a for Pr123, Fig.2b for Y123 (from ref. [6]), and Fig.2c for Y124. The evolution of the c-axis with the applied hydrostatic pressure for Pr123 is shown in Fig.3a in comparison with the corresponding one for the optimally doped Y123 (Fig.3b) from ref.…”

“…The evolution of the c-axis with the applied hydrostatic pressure for Pr123 is shown in Fig.3a in comparison with the corresponding one for the optimally doped Y123 (Fig.3b) from ref. [6], whereas the results for Y124 are presented in Fig.3c. Full symbols represent the values for increasing the pressure and open symbols those for releasing the pressure.…”

“…Recent structural investigations, using synchrotron angle-dispersive powder diffraction and dense sampling on optimally doped Y123 superconductor, have revealed in the pressure range 3.7 GPa<p<10 GPa a clear deviation of the lattice constants from the expected EOS, strong hysteresis effects, and the formation of an additional new textured phase [6]. Interatomic distances in the unit cell of Y123 such as the Ba distance from the basal plane, the Cu2-O pl bond length, and the Cu2-Cu1 distance along the c-axis have been found to exhibit also a non linear evolution with applied pressure that correlates with modifications of the Raman spectra of the in-phase O pl and the O ap phonon modes [6]. The correlation of the structural characteristics with the Raman frequency modifications [6] and corresponding changes of T c [7] imply that the trigger of the lattice instabilities lies among the CuO 2 and BaO planes.…”

“…Interatomic distances in the unit cell of Y123 such as the Ba distance from the basal plane, the Cu2-O pl bond length, and the Cu2-Cu1 distance along the c-axis have been found to exhibit also a non linear evolution with applied pressure that correlates with modifications of the Raman spectra of the in-phase O pl and the O ap phonon modes [6]. The correlation of the structural characteristics with the Raman frequency modifications [6] and corresponding changes of T c [7] imply that the trigger of the lattice instabilities lies among the CuO 2 and BaO planes. Charge redistribution among the planes, that has been found to occur in the case of chemical pressure [11], also affects the T c , and must certainly play a role in the observed effects.…”