Structure and properties of high piezoelectric coupling Pb(B′_½Nb_½)O₃-PbTiO₃ binary systems

Abstract

The (1-x)Pb(Lu_½ Nb_½)O₃-xPbTiO₃ and (1-x)Pb(Er_½ Nb_½)O₃-xPbTiO₃ binary systems have been obtained, the structure and properties of which are studied. The unit cell of erbium niobate (PErN) is described as pseudomonoclinic of orthorhombic Bmm2 symmetry: a=c=4.2161 Å b=4.0869 Å β=90.55° and composition is characterized with antiferroelectric phase transition at 305°C. The PErNT system has the morphotropic phase region extending over the x=0.4–0.6 interval. In PLuNT ceramics system the pseudomonoclinic phase structure Bmm2 extending over the 0≤x ≤0.38 interval becomes pseudocubic at x≈ 0.2. The morphotropic region is spread over 0.38< × < 0.49; at higher PT concentrations (1.0 ≥ × ≥ 0.49) the structure transfers to the tetragonal P4mm phase. The maximum values of the electromechanical coupling coefficients k_p=0.66, k_t=0.48, k₃₁=0.35 were attained in compositions PLuNT 59/41 near the morphotropic phase boundary.

Key Words:

• piezoelectric ceramics
• binary systems
• lutecium niobate
• erbium niobate
• relaxor
• phase diagram
• dielectric and electromechanical properties