Substrate temperature dependent properties of sprayed CoFe2O4 ferrite thin films

The CoFe2O4 ferrite thin films have been prepared by spray pyrolysis technique at different substrate temperatures (T-s). The XRD patterns reveal a good (111) texture in the film prepared at T-s = 325 degrees C. The slow scan XRD studies show that the grain size is of the order of 150 Angstrom and is not varied much with the substrate temperature. The lattice parameter a calculated from XRD data is found to be larger than the bulk value. This indicates that the spray deposited CoFe2O4 films are under a compressive stress in the film plane. The electrical resistivity measurements show a increase in resistivity with decrease in temperature exhibiting a semiconducting behaviour. Tne thermoelectric power measurements reveal that the films prepared at T-s = 325, 335 and 345 degrees C showed n-type conductivity whereas that at T-s = 355 degrees C exhibited p-type conductivity. This change in conductivity can be attributed to change in cation distribution, which is found to be depend on substrate temperature. (C) 1998 Elsevier Science S.A. All rights reserved.