WO3 and LaFeO3 are considered as example oxides in gas sensing, respectively of perovskitelike BO3 and ABO3 oxide groups, the structural chemistry of which is based on corner-sharing octahedral oxygen networks where transition metal cations B occupy the octahedral cages of oxygen anioins. WO3 is an n-type semiconductor and many magnetic perovskites like LaFeO3 are p-type semiconductors. There is a great flexibility inherent in the structure of both oxide groups which gives a lot of possibilities for structure engineering of the oxides for gas-sensing applications, e.g., by a temperature treatment or by modifying with impurity atoms. We have used here a high-temperature process, advanced reactive gas deposition, to produce nanoparticle thick films of WO3 with the metastable tetragonal crystal structure at low temperatures up to 300-400°C, and sol-gel citrate method to produce nanocrystalline LaFeO3 powder as pure and modified with Sr and Mg, respectively. © 2004 Kluwer Academic Publishers.