This paper is devoted to the study of elastic matching of phases coexisting in systems of perovskite-type solid solutions close to morphotropic phase boundaries. Determined are different interfaces that separate single-domain or polydomain phases in $\left(1\mathrm{}-x\right){\mathrm{PbZn}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_3-x{\mathrm{PbTiO}}_3$ single crystals and ${\mathrm{PbZr}}_{1-x}{\mathrm{Ti}}_x{\mathrm{O}}_3$ ceramic grains. These interfaces are parallel to so-called zero net strain planes. Some results of recent experimental studies of the crystal structure and electromechanical properties are analyzed in connection with the revealed simplification of the domain structure in the intermediate monoclinic phase of $\left(1\mathrm{}-x\right){\mathrm{PbZn}}_{1/3}{\mathrm{Nb}}_{2/3}{\mathrm{O}}_3-x{\mathrm{PbTiO}}_3$ single crystals. The important role of the monoclinic phase in relieving stress at the phase coexistence in both the systems is considered. Links between optimal domain volume concentrations derived from unit-cell parameters’ behavior are discussed on the basis of concepts of the polarization rotation path proposed by Fu and Cohen [Nature (London) 403, 281 (2000)].

• Received 10 September 2001

DOI:https://doi.org/10.1103/PhysRevB.65.094207