  We have derived the interaction between Jahn-Teller centers due to optical
and acoustic phonons. Without Coulomb repulsion the model leads to a global
phase separation at low temperature. At long distances Coulomb repulsion always
dominates the short range attraction leading to phase separation on a short
scale. On the basis of Monte-Carlo simulation of microscopic lattice-gas model
we have formulated an effective phenomenological model. In the limit of low
density of polarons, phase separation takes place in the form of charged
bubbles. In the limit of high density, charge segregation occurs on domain
walls.
