In the present study was combined the use of high resolution TGA with the isoconversion method, giving us a suitable methodology for determining the stages that occur during a reaction, and providing further insights about the kinetics of the processes involved. As a model reaction was used the thermal dehydration of KNbWO(6)center dot H2O. The results shown that the dehydration process is controlled by internal water diffusion (intra-crystallite); with activation energy values between 43 and 36 kJ/mol. This value is consistent with a diffusion mechanism dominated by van der Waals attractions. The estimated kinetic parameters are supported with a structural analysis, that suggest lower dimensionality character for water diffusion due to the specific orientations of < 110 > open channels in the pyrochlore framework. This would explain why the two-dimensional (D2) mechanism appears to be the most probable. (C) 2005 Published by Elsevier B.V.