Concentration phase diagram of BaxSr1-xTiO3 solid solutions

Method of derivation of phenomenological thermodynamic potential of solid solutions is proposed in which the interaction of the order parameters of constituents is introduced through the account of elastic strain due to misfit of the lattice parameters of the end members. The validity of the method is demonstrated for the BaxSr1-xTiO3 system being a typical example of ferroelectric solid solution. Its phase diagram is determined using experimental data for the coefficients in the phenomenological potentials of SrTiO3 and BaTiO3. In the phase diagram of the BaxSr1-xTiO3 system for small Ba concentration, there are a tricritical point and two multiphase points one of which is associated with up to six possible phases.