Fabrication of textured KNNT ceramics by reactive template grain growth using NN templates

摘要

Lead-free non-stoichiometric (K_(0.470)Na_(0.545))(Nb _(0.55)Ta_(0.45))O_3 (KNNT) textured ceramics were prepared by a reactive templated grain growth method using NaNbO_3 (NN) templates. The Plate-like NaNbO_3 (NN) templates were synthesized from bismuth layer-structured Bi_(2.5)Na_(3.5)Nb _5O_(18) (BNN) particles by a topochemical microcrystal conversion (TMC) method. Using 5 wt% of NN templates, textured KNNT ceramics were fabricated, and their crystal structure, microstructure, dielectric and piezoelectric properties were compared with non-textured KNNT ceramics prepared by a conventional solid state reaction method. The textured KNNT ceramics exhibited high grain orientation and high dielectric constant. In addition, piezoelectric properties of textured KNNT ceramics were improved, giving a high piezoelectric coefficient d_(33) = 390 pC/N and piezoelectric coupling coefficient k_p = 0.60.