| 초록 |
In this work, [ $Pb(Mg_{1/2}W_{1/2})_{0.03}(Ni_{1/3}Nb_{2/3})_x(Zr_{0.5}Ti_{0.5})_{0.97-x}O_3-BiFeO_3$ ] (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 $BiFeO_3$ , $Li_2CO_3$ , and $CaCO_3$ 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 $CaCO_3$ , $Li_2CO_3$ . 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 $920^{ circ}C$ showed the optimum values of piezoelectric constant( $d_{33}$ ), piezoelectric figure of merit( $d_{33{ cdot}}g_{33}$ ), planar piezoelectric coupling coefficient( $k_p$ ) and density : $d_{33}=566$ [pC/N], $g_{33}=29.28[10^{-3}mV/N]$ , $d_{33{ cdot}}g_{33}=16.57[pm^2/N]$ , $k_p=0.61$ , density=7.82 [ $g/cm^3$ ], suitable for duplex ultrasonic sensor application. |
