6533b7d1fe1ef96bd125c152

RESEARCH PRODUCT

Structure and Properties of Novel Pb(B’1/2Nb1/2)O3-PbTiO3 Binary Systems with High Piezoelectric Coupling

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The (l-x)Pb(Lu1/2Nb1/2)O3-xPbTiO3 (PLuNT) and (l-x)Pb(Er1/2Nb1/2)O3-xPbTiO3 (PErNT) binary systems have been originally synthesized. Pure lutecium niobate (PLuN) (x = 0) has a pronounced long-range order in the B-sublattice and an antiferroelectric to paraelectric phase transition at ~258°C. The phase structure of the PLuNT system, at room temperature, changes from a pseudomonoclinic (psd-M, space group Bmm2) to tetragonal (T, space group P4mm). The pseudomonoclinic phase extends over the 0 ≤ x ≤ 0.38 interval within which the monoclinic angle β proceeds a minimum near to 90° at x≅0.2. The morphotropic region covers over the interval x = 0.38–0.49, the concentration ratio psd-M:T≅l (the morphotropic phase boundary — MPB) corresponds to x = 0.41. Dielectric dispersion and broadening of the phase transition — features typical to relaxors are observed within the concentration interval of 0.1 ≤ x ≤ 0.3. The highest electromechanical coupling coefficients: kp = 0.66, kt = 0.48, k31 = 0.34 of (l-x)PLuN — xPT ceramics are attained in compositions near the MPB at x≈0.41. Non-isovalent doping of PLuNT with La3+ in Pb sublattice shifts the MPB to lower values of x.