97-28E

The dielectric properties of two-sublattice Hubbard model with local anharmonicity and direct interaction between pseudospins are considered within mean field approximation and one-loop approximation. Such a model can be used for the description of dielectric properties of YBaCuO-type superconductors along $c$-axis (the pseudospins represent an anharmonic motions of apical oxygen O4). The behaviour of the the transverse dielectric susceptibility $\chi _\perp $ is considered in the noninteracting clusters approximation. The regions of model parameters, where phase transitions into phases with noncompensated ordering of pseudospins are established. It is proposed the method how to avoid the additional (nonphysical) phase transition within one-loop approximation (the first order of high-density expansion method).