A polymerizable-complex powder synthesis method (PCM) was used in conjunction with automated solution deposition to generate combinatorial libraries of oxide powders doped with alkali metals. Chemical compositions were serially examined with automated thermogravimetric analysis for catalytic activity in the combustion of diesel soot. The relative soot combustion activity of KxLa1-xFeO3, FeO3, A(2x)Cu(1-x)Fe(2)O(4) and A(2x)Co(1-x)Fe(2)O(4) (A = Li, Na, K, Cs) are reported. In both of the alkali-metal doped systems, K was the best promoter of soot oxidation, In all three systems, K-rich samples in the "mixed" range (x = 0.6-0.9) generally show the lowest soot oxidation temperatures. (C) 2004 Elsevier B.V. All rights reserved.