Nonstoichiometry of the perovskite-type solid solutions La0.9Ca0.1Cr1-yAlyO3-delta was studied by high-temperature gravimetry under controlled P(O-2) atmospheres of 1-10(-23) bar at 1073-1273 K. The observed data were described by a regular solution-like model for the randomly distributed defects of V-O(..), Cr-Cr(.), Ca-La',and Al-Cr(X). With the increase in y, V-O(..) formation becomes much easier. For y > 0.8, some fraction of Ca-La', becomes surrounded only by Al-Cr(X) and V-O(..) remains around such Ca-La' up to high P(O-2) to reduce the maximum oxygen content below 3.000. (c) 2006 Elsevier B.V. All rights reserved.