In this work, [Pb(Mg1/2W1/2)0.03(Ni1/3Nb2/3)x(Zr0.5Ti0.5)0.97-xO3-BiFeO3] (x=0.02 to 0.12) composition ceramics were fabricated by the conventional soild state reaction method and their microstructure and piezoelectric properties were investigated according to PNN substitution. The addition of small amount of BiFeO3, Li2CO3, and CaCO3 were used in order to decrease the sintering temperature of the ceramics. The XRD (x-ray diffraction patterns) of all ceramics exhibited a perovskite structure. The sinterability of PMW-PNN-PZT-BF ceramics was remarkably improved using liquid phase sintering of CaCO3, Li2CO3. However, it was identified from of the X-ray diffraction patterns that the secondary phase formed in grain boundaries decreased the piezoelectric properties. According to the substitution of PNN, the crystal structure of ceramics is transformed gradually from a tetragonal to rhombohedral phase. The x=0.10 mol PNN-substituted PMW-PNN-PZT-BF ceramics sintered at 920 showed the optimum values of piezoelectric constant(d33), piezoelectric figure of merit(d33·g33), planar piezoelectric coupling coefficient(kp) and density : d33=566 [pC/N], g33=29.28 [10-3mV/N], d33·g33=16.57 [pm2/N], kp=0.61, density=7.82 [g/cm3], suitable forduplex ultrasonic sensor application.
