Thin SnO2 films doped with Zr and Pd are obtained by the spray-pyrolysis method. The films are sensitive to 0.1 ppm phosphine at an operating temperature of 250-400 °C. The sensitivity, response and recovery time are studied as a function of the Zr concentration. The chemical and phase compositions and microstructure of the films obtained are investigated by EDX, XRD and SEM analyses. The strong influence of Zr on the microstructure and gas-sensing characteristics of the films has been established. © 1994.