Fe2-xYxW3O12 powder has been synthesized by the citrate sol-gel process. A model was proposed to calculate the concentration of species in a citric solution. The calculated results could provide valuable information for determining the optimal molar ratio of cation to citric acid and pH value of solution for Fe2-xYxW3O12 preparation. The predicted parameters derived from this model are in good agreement with the experimental results. The prepared gel and the Fe2-xYxW3O12 powder were characterized by X-ray diffraction (XRD) and differential thermal analysis-thermo-gravimetry (DTA-TG). The results show that it is very difficult to obtain pure Fe2W3O12 powder by the citrate sol-gel process in the temperature range 500 degrees-1000 degrees C, however, Y2W3O12 can easily be prepared even at 500 degrees C. Y2W3O12 annealed at 1000 degrees C for 10 h is favorable for absorbing moisture in air to form Y2W3O12 center dot 3.3H(2)O. The thermal expansion coefficients of Y2W3O12 center dot 3.3H(2)O are: alpha(a) = 8.01 x 10(-6)degrees C-1, alpha(b) = 2.51 x 10-7 degrees C, and alpha c = -5.55 x 10-6 degrees C-1 in 473-1173 K.