To investigate excess Na⁺ effect, Bi_0.5(Na_0.78+xK_0.22)0.5TiO₃ (0≤x≤0.05) (BNKT) ceramics were prepared by using a conventional solid-state reaction method. The structure and ferroelectric properties of BNKT ceramics were characterized by XRD (X-ray diffraction) and polarization dependence by external electric field. Also, the temperature dependence of dielectric constant and loss were studied. From these results, it was found that appropriate excess Na⁺ into BNKT ceramics compensate the volatility and induce dense ceramics. The enhanced piezoelectric coefficient (158 pC/N) and depolarization temperature (202℃) were obtained for the x=0.01 composition.

Eco-friendly (Na, K) Nb03 (NKN)-based piezoelectric ceramic materials were fabricated by conventional ceramic method for shear mode piezoelectric energy harvesting application. NKN-LiTaO3 (LT) based compositions were adopted for the high d15xg15 which is proportional to harvested energy density. The composition 0.935(Na0.535K0.485) NbO3-0.065LiTaO3 was found to be lie on the boundary of tetragonal and orthorhombic phases. With reducing Ta content, the dielectric constant decreased gradually while maintaining high d15, which resulted in increased d15xg15, The composition 0.935(Nao0.535K0.485)) NbO-0.065Li (Nb0.990Ta0.0010) O3 was found to possess excellent piezoelectric and electromechanical properties (d15sxg15 =29 pm2/N, d13 417pC/N, k15= 0.55), and high curie temperature (T 455t).

Additions (ZnO, CuO) doped 0.98(Na0.5K0.5)NbO3-0.02Li(Sb0.17Ta0.83)O3 (0.98NKN-0.02LST-x) lead free piezoelectric ceramics have been fabricated by ordinary sintering technique. The effects of additions doping on the dielectric, piezoelectric, and ferroelectric properties of the ceramics were mainly investigated. X-ray diffraction of the sample appeared orthorhombic phase. The specimen doped with additions exhibits enhanced electrical properties (d33= 153 pC/N). These results indicate that the 0.98NKN-0.02LST-x ceramics is a promising candidate for lead-free piezoelectric ceramics for applications such as piezoelectric actuators, harmonic oscillator and so on.

We studied sintering temperature to enhance the piezoelectric properties of 0.98(Na0.5K0.5)NbO3-0.02Li(Sb0.17Ta0.83)O3+0.01wt%ZnO (hereafter NKN-LST+ZnO) lead free piezoelectric ceramics. The synthesis and sintering method were the conventional solid state reaction method and sintering was executed at 1,080∼1,120℃. We found that NKN-LST+ZnO ceramics at optimal sintering temperature showed the improved piezoelectric properties at the optimal sintering temperature. The NKN-LST+ZnO ceramics show good performance with piezoelectric constant d33= 153 pC/N sintered at 1,090℃. The results reveal that NKN-LST+ZnO ceramics are promising candidate materials for lead-free piezoelectric application.

The effect of lead free glass frit compositions on the properties of thick film conductor and resistor pastes were investigated. Two types lead free frits, HBF-A(without Bi2O3) and HBF-B(with Bi2O3) were made from SiO2, B2O3, Al2O3, CaO, MgO, Na2O, K2O, ZnO, MnO, ZrO2, Bi2O3. And Ag based conductor pastes and RuO2 based resistor paste were prepared by mixed with these frits and functional phase(Ag and RuO2), and organic vehicle. The properties of thick film conductor and resistor sintered at 850℃ were studied after printing on Al2O3 substrate. The morphology of the sintered films surface were SEM and EDS were carried out to analysis the chemical composition on resistor surface and state of Ru atom in frit matrix.