Departamento de Fsica, Universidade Federal de Minas Gerais,

The Ising model has been an important theoretical tool in the understanding of phase transitions in ferroelectric materials. We rst review how it relates to the underlying physics of order-disorder phase transitions in these systems, as well as mean-eld results for the spontaneous polarization and the dielectric constant near the critical temperature. For hydrogen-bonded ferroelectrics, a term of interaction with an external transverse eld is necessary to account for proton tunneling between the two minima of a double-well potential. Finally, we discuss both experimental and theoretical results for the problems of proton-lattice interactions, central peak dynamics, dynamical behavior of pseudo-one-dimensional ferroelectrics and pressure eects on hydrogen bonded ferroelectrics.