EFFECT OF MnO₂ ON THE ELECTRICAL PROPERTIES OF 0.96KNNT-0.04BNZ LEAD-FREE PIEZOELECTRIC CERAMICS

0.96(K 0.49 Na 0.51 )(Nb 0.97 Ta 0.03 )O3-0.04Bi 0.5 Na 0.5 ZrO 3 + x mol. % MnO 2 (0.96KNNT-0.04BNZ + x mol. % MnO 2 , x = 0, 0.1, 0.2, 0.4, 0.6, 0.8) lead-free piezoelectric ceramics were prepared via conventional solid state method. The effect of MnO 2 doping content on the structure and electrical properties of 0.96KNNT-0.04BNZ ceramics was investigated. All samples had pure perovskite structure with coexistence of orthorhombic and tetragonal phases at room temperature. The 0.96KNNT-0.04BNZ + 0.2 mol. % MnO 2 ceramic sample exhibited enhanced piezoelectric constant (d 33 = 330 pC/N) and planar electromechanical coupling coefficient (k p = 38.8 %). In addition to other optimized electrical properties such as medium high dielectric permittivity (( 33 T ) 0 = 1370) and mechanical quality factor (Q m = 135), relatively low dielectric loss (tan = 2.4 %) and high Curie temperature (T c = 305 C), this ceramic sample should be a promising lead-free alternative to toxic leadbased piezoelectric materials.