Ordered micro-regions and dielectric properties of La³⁺-doped Pb(Zn_1/3Nb_2/3)O₃-based ceramics with Nb ⁵⁺ deficiency

La³⁺-doped 0.85Pb(Zn_1/3Nb_2/3)O ₃-0.10BaTiO₃-0.05PbTiO₃ (abbreviated as PZN-based ceramics hereafter) ternary system ceramics with Nb⁵⁺ deficiency were synthesized by the columbite method. The effect of deficient Nb⁵⁺ on the phase structure, ordered micro-region size and dielectric properties of lanthanum-doped PZN-based ceramics was investigated in detail. With the increase of Nb⁵⁺ deficiency, the content of pyrochlore phase decreased significantly. Especially, when Nb⁵⁺ deficiency was >3 mol%, the pyrochlore phase resulting from La³⁺ doping was eliminated completely. From the viewpoint of the phase structure affected by Nb⁵⁺ deficiency, it could come to the conclusion that the non-stoichiometric 1:1 ordered micro-regions do exist in PZN-based ceramics. The analysis of Raman scattering spectra demonstrated that Nb⁵⁺ deficiency enlarged ordered micro-region size of the lanthanum-doped PZN-based ceramics. Nb⁵⁺ deficiency increased the dielectric constant, but it hardly affected dielectric loss. The increase of dielectric constant results not only from the elimination of pyrochlore phase but also from the size increase of "effective ordered micro-regions".