Ranian Study of Compositionally Induced Phase Transitions in Nd_(1-x)Ba_(2-x)Cu_3O_z Solid Solutions

摘要

In the present research we studied single phase Nd123ss within a wide range of compositions x=0...0.9 by Ramanspectroscopy. For such solid solutions we observed the increaseof the area of Raman-active apical oxygen mode for x=0. - .0.5,and its decrease for higher Nd content, which can be explainedby existence of non-random distribution of Nd in Ba(Nd)Olayers for x>0.6 resulting in formation of orthorhombic structureof 213. Nevertheless observed Raman, IR-spectra and highoxygen content of Nd-2 13 (z=7.30) are inconsistent withstructural model proposed before. It was found that single phaseNdBa_2Cu_3O_7 prepared at low oxygen partial pressuredecomposes into BaCuO_2 and Ndl23ss after subsequentannealing in oxygen at temperature higher than 700degC.