  It is demonstrated that the substances with small difference in the free
energies of the ferroelectric and antiferroelectric phases possess a set of
properties characteristic for the so-called "dipole glasses". Possible phase
diagrams of the substances that can be misguidedly attributed to glasses are
discussed. Main attention has been paid to the process of long-time relaxation
of physical characteristics of these compounds after their state of
thermodynamic equilibrium was disturbed by external influences. The long-time
relaxation along with the pronounced frequency dependence of parameters (for
example, dependence of dielectric or magnetic characteristics on the frequency
of measuring field) is considered as main features due to which these systems
are classified as dipole glasses. Our main purpose is to call attention to the
fact that one has to be cautious during the interpretation of experimental
results in substances with inhomogeneous states of coexisting domains of
ferroelectric and antiferroelectric phases.
