A series of perovskite-type compounds La1 - xCaCr0.5Ti0.5O3 -delta (x = 0...1.0) was synthesized by a ceramic technique in air (final heating 1350 degreesC). The crystal structures of the compounds were characterised at room temperature for 0.00.2 as orthorhombic in space group Pbnm. The lattice constants with increasing Ca contents for x>0.5 decrease noticeably and for x < 0.5 remain nearly constant. All compositions were stable at pO(2) = 2 1,000 to 6 x 10(-16) Pa at 850...1000 degreesC. Oxygen stoichiometries and electrical conductivities of the solid solutions were investigated. The stability of the oxides against thermal dissociation evaluated by the oxygen release decreases with increasing Ca-contents. The compounds with x greater than or equal to 0.6 are p-type and with x < 0.4 n-type semiconductors at 900 degreesC and oxygen partial pressures between 1 x 10(-15) and 0.21 X 10(5) Pa. La0.5Ca0.5Cr0.5Ti0.5O3 (-) (delta) and La0.6Ca0.4Cr0.5Ti0.5O3 - delta change their conductivities from n-type in the range pO(2) < 10 (-10) Pa and pO(2) < 10 (-5) Pa, respectively, to p-type in more oxidizing atmosphere. For the compound with x = 0.5 in Ar/H-2/H2O gas flow (pH(2)O/pH(2) = 0.53) at 900 degreesC a maximum conductivity of about 1 S/cm has been observed. In air the composition with x = 0.75 has highest conductivity of about 40 S/cm. Partial substitution of calcium by lanthanum leads to a decrease of the average thermal expansion coefficients (TEC) from 13.1 X 10 (-6) K (-1) (CaCr0.5Ti0.5O3) to 10.5 X 10 (-6) K-1 (La0.25Ca0.75Cr0.5Ti0.5O3) and 9.5 X 10 (-6) K (-1) (La-0.5.Ca0.5Cr0.5Ti0.5O3). No simple correlations between catalytic activity, electrical conductivity, and crystal structure parameters were found. (C) 2003 Elsevier Science B.V. All rights reserved.