Dielectric and piezoelectric properties of Pb(Ni_1/3Nb_2/3)O₃-PbTiO₃-PbZrO ₃ ceramics modified with bismuth and zinc substitutions

The dielectric and piezoelectric properties of the (Pb_0.985Bi_0.01)(Ni_1/4Zn_1/12Nb _2/3)_x-(Zr_σTi_1-ι) _1-xO₃ piezoelectric ceramic system (0.2 ≤ x ≤ 0.7, 0.1 ≤ σ ≤ 0.9) were systematically investigated. The results showed that, after poling, the dielectric constant, ε^T₃₃, increased for the tetragonal compositions but decreased for the rhombohedral compositions. Furthermore, high values of ε^T₃₃ and piezoelectric modulus, d₃₁ were found for the compositions along the extension of the morphotropic phase boundary. The highest values of the planar electromechanical coupling factor, K_p, and the piezoelectric modulus, d₃₁, were found to be 0.70 and -274 × 10 ^-12 CN ^-1, respectively. The Curie temperature, remanent polarization, coercive field and the lattice constants of the a and c axes in relation to the Pb(Ni_1/3Nb_2/3)O₃ content and the Zr/Zr + Ti ratio were also determined.