  The model for calculation of relaxor ferroelectrics thin films properties is
proposed. The basis of the model is the theory of random field. This field is
originated from the chemical disorder allowing for influence of the film
surfaces, which destroys the polar long-range order and transform it into mixed
state of ferroelectric glass (FG) or dipole glass (DG). The spatial profiles
and averaged over coordinate inside the film values of properties of relaxor
ferroelectric film were calculated with the random field distribution function.
As an example the dependence of the order parameter on film thickness,
temperature and distribution function characteristics was obtained. The
critical thickness and temperature of the size-driven phase transition from FG
to DG state as a function of the film and distribution function characteristics
were calculated.
