Synthesis and neutron powder diffraction study of Tb2-xBa2+xCu2+yTi2-yO11

Samples of the quadruple perovskites Tb2-xBa2+xCu2+yTi2-O11 have been prepa red for values of x = 0.0 and 0.2 and y = 0.0 and 0.1. The prepared samples were studied by neutron powder diffraction and Cu/Ti and Nd/Ba cation diso rder was found to be present in all three studied compounds and the excess Ba in the x = 0.2 samples are located in the Tb 1d(1/2 1/2 1/2) site while the Tb 1c (1/2 1/2 0) site between the CuO2 layers is fully occupied by Tb ions. In addition, it was found that no Ti is substituted for Cu in the CuO 2 layers in the Tb1.8Ba2.2Cu2.1Ti1.9O11 sample. (C) 2001 Elsevier Science B .V. All rights reserved.