(Bi _0.5 Na _0.5 )(Zr _0.97 W _0.01 Fe _0.02 )O ₃ doping effects on KNN‐based lead‐free ceramics prepared via two‐step sintering technique

Abstract (1‐x)(Li _0.02 Na _0.5 K _0.48 )(Nb _0.95 Sb _0.05 )O ₃ ‐x(Bi _0.5 Na _0.5 )(Zr _0.97 W _0.01 Fe _0.02 )O ₃ (LNKNbS‐xBiNZWF, x = 0.035, 0.04, 0.045, 0.05, and 0.055) lead‐free piezoceramics were fabricated by traditional solid‐state sintering method via two‐step sintering technique, where the effects of BiNZWF doping amount and ceramic processing were studied systematically. The formation of orthorhombic‐tetragonal (O‐T) phase boundary in the LNKNbS‐xBiNZWF system is confirmed by X‐ray diffraction Rietveld refinement and Raman spectroscopy, where the BiNZWF doping amount affects the O‐T phase proportion. The LNKNbS‐xBiNZWF ceramics approach to normal ferroelectrics but have apparent relaxation characteristic. Oxygen vacancies dominate the high‐temperature conduction in the LNKNbS‐0.04BiNZWF ceramics, which are generated by the volatilization of Bi and alkali metals during sintering. The LNKNbS‐0.04BiNZWF ceramics exhibit excellent electrical properties, correlating with using the two‐step sintering method, appropriate proportion of O phase and T phase, high densification and improved microstructure uniformity.