(Na,K)NbO3-based piezoelectric ceramics were synthesized by a solid phase sintering method with various milling solvents. The solvents were varied with acetone, ethanol, and pure water to investigate the effect on the microstructure and electrical properties. NKN ceramics showed the maximum values of the relative density (94%), the mechanical quality factor (Qm: 78) and the electro-mechanical coupling factor (kp: 0.25) at the ethanol solvent. It might mean that a solid phase sintering of the NKN piezoelectrics with a suitable solvent could improve the relative density and the piezoelectric properties.
In this study, lead-free Piezoelectric (Na0.47K0.47Sr0.03Ca0.03)(Nb0.94Ti0.06)O3-0.1 MnO2 ceramics werefabricated using mixed oxide method and the effects of various sintering temperature on the structural andelectrical properties were investigated. For the (Na0.47K0.47Sr0.03Ca0.03)(Nb0.94Ti0.06)O3-0.1 MnO2 (NKN-SCT-MnO2)ceramics sintered at temperatures of 1,025∼1,100℃. The results indicated that all specimens were perovskitesingle phase formation without any second phase. It has been shown that relative density is increased toincreasing sintering temperature. When the sintered temperature at 1,075℃, highest sintered density andmaximum value of 4.45 g/cm3. Average grain size is increased to increasing sintering temperature. Theelectromechanical coupling factor, dielectric constant, dielectric loss, d33 and curie temperature at the sinteringtemperature 1,075℃ of NKN-SCT-MnO2 specimens were 0.22, 511, 0.033, 103 and 380℃, respectively.
In this study, KNbO3-substituted (Li,Na,K)(Nb,Sb,Ta)O3 ceramics were investigated to develop Pb-free composition ceramics for multilayer actuator and energy harvester applications. The X-ray diffraction analysis indicated that all samples were pure perovskite phase and no secondary phase was found. A tetragonality as a function of KNbO3 substitution showed the maximum value at 1.5 mol% KNbO3 and then decreased. The SEM image analysis showed the maximum grain size of 3.14 ㎛ at 1.5mol% KNbO3. In the composition ceramics with 1.5 mol% KNbO3 sintered at 1,100℃, excellent properties of density= 4.75 g/cm3, electromechanical coupling factor (kp)= 0.50 and piezoelectric constant(d33)= 290 pC/N were obtained, respectively, suitable for piezoelectric actuator and energy harvester applications.
The most widely used piezoelectric ceramics are lead oxide based ferroelectrics (PZT). However, the toxicity of lead oxide and its high vapor pressure during processing have led to a demand for alternative lead-free piezoelectric materials. We synthesized Lead-free piezoelectric ceramics of 0.96(K0.5Na0.5)NbO3-0.04SrZrO3+x mol% ZrO2 [KNN-SZ+xZrO2; x= 0～0.10] doped with 0.1 wt% MnO2 by a conventional solid state method. We investigated the piezoelectric properties and microstructures of these disk samples sintered in reduced atmosphere in order to evaluate the possibility of the multilayered piezoelectric ceramics having the base metal such as Ni as a internal electrode. All of these KNN-SZ samples sintered in 3%H2-97%N2 atmosphere at 1,140℃ exhibit pure perovskite structure irrespective of the content of ZrO2. Meanwhile, the sintering denisty and piezoelectric properties such as Kp, Qm and d33 of KNN-SZ samples as a function of ZrO2 content show the maxima (kp= 28.07%, Qm= 101.34, d33= 156 pC/N) at x= 0.04 and it is likely that there is some morphotropic phase boundary(MPB) in this KNN-SZ+xZrO2 composition system. These results indicate that the ceramic composition is a promising candidate material for applications in lead free multilayer piezoelectric ceramics.
First
Prev
