Structural properties of the Gd2O3-ZrO2 system, xGdO(1.5)-(1-x)ZrO2 with 0.18 less than or equal to x less than or equal to 0.62, were investigated by Gd-155 Mossbauer spectroscopy and powder X-ray diffraction. The results indicated that local arrangements around the Gd3+ ions are similar in the fluorite (F)- and pyrochlore (P)-type compounds for 0.18 less than or equal to x less than or equal to 0.50, whereas they vary slightly for 0.50 < x less than or equal to 0.62. Displacements of the six oxygen ions in the 48f site from the ideal position of the related F-type compound increase with increasing x for 0.18 less than or equal to x less than or equal to 0.50 and decrease slightly for 0.50 less than or equal to x less than or equal to 0.62. The displacement is the largest in the stoichiometric P-type Gd2Zr2O7 (x=0.50). (C) 2003 Elsevier B.V. All rights reserved.