Lead-free bismuth sodium titanate (BNT)-based ceramics have attracted strong attention as environmentally benign dielectric materials for high-efficiency electrostatic energy-storage capacitors. A key challenge is that pristine BNT typically exhibits large hysteresis, high remnant polarization, and limited dielectric reliability, which restrict recoverable energy storage and efficiency under practical electric fields. Here, we present a focused mini-review of recent studies to clarify how composition design, phase boundary tuning, defect chemistry, and microstructural control collectively enable slim or pinched polarization-electric field (P-E) behavior and improved energy-storage functionality in BNT-related bulk ceramics. The reviewed outcomes consistently show that stabilizing relaxor states governed by polar nanoregions (PNRs), often via solid-solution engineering and secondary relaxor/antiferroelectric-like incorporation, suppresses irreversible switching and reduces hysteresis loss, while densification and grain-size control enhance electrical homogeneity and breakdown strength. In addition, defect-mediated tuning of oxygen vacancy-related complexes is highlighted as an independent lever to control relaxor ergodicity and polarization reversibility, providing a complementary route to slim-loop optimization. These insights are expected to guide integrated design strategies that couple phase/relaxor-state engineering with defect and microstructure optimization, accelerating the development of reliable, temperature-robust, lead-free dielectric capacitors based on BNT-related ceramics.

(Bi_1/2Na_1/2)TiO₃(BNT) piezoelectric ceramics are one of the promising materials that can replace Pb(Zr, Ti)O₃(PZT) piezoelectric ceramics due to the high electromechanical strain properties. However, it is still difficult to use practical applications because the required electric field for inducing electromechanical strain is relatively higher than that of PZT ceramics. To overcome this problem, it has been intensively studied on doping impurity or modifying other ABO₃ for BNTbased piezoelectric ceramics. Therefore, this study investigated the effects of La₂O₃ doping on the phase transition behavior and electromechanical strain properties in BNT-SrTiO₃ (BNT-ST) lead-free piezoelectric ceramics. In the case of the temperaturedependent dielectric properties, it was confirmed that a phase transition from ferroelectrics to relaxors is induced with increasing La₂O₃ content. As a result, the electromechanical strain properties of BNT-ST ceramics were improved. The highest Smax/Emax value corresponding to 300 pm/V was obtained at 2 mol% La₂O₃-dopped BNT-ST ceramics. Accordingly, this study successfully demonstrated that La₂O₃ doping is effective on the inducing phase transition from ferroelectrics to relaxors and the improving electromechanical strain properties of BNT-ST lead-free piezoelectric ceramics.

Piezoelectric ceramics play an important role in various electronic applications. However, traditional ceramics are difficult to be used in some complicated structures, due to their low flexibility and high brittleness. To solve this problem, this study prepared and investigated ceramic/polymer composites that can utilize a good flexibility of polymers. Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) and 0.77(Bi_1/2Na_1/2)TiO₃-0.23SrTiO₃ (BNST23) ceramics were selected to fabricate the composites. Ceramic/polymer composites were prepared using various volume fractions of BNST23 ceramics. The distribution of piezoceramic particles in BNST23/PVDF-TrFE composites was investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The dielectric and piezoelectric properties of the composites were significantly influenced by the volume fraction of the piezoelectric ceramics. As a result, the highest piezoelectric constant (d33) of 56 pC/N was obtained in a composites with 70% volume fraction of BNST23 ceramics. Accordingly, it is expected that BNST23/PVDF-TrFE composites can be applied to various sensor applications.

It was reported that a tetragonal phase can be stabilized with maintaining good piezoelectric properties when Na_0.5K_0.5NbO₃ (KNN) is modified with 0.06 mol SrTiO₃. However, such a high amount of SrTiO₃ leads not only to poor sinterability but low Curie temperature (TC). To maintain high TC with good piezoelectric properties in KNN-based lead-free piezoelectric ceramics, this study investigates the effect of Li-doping on the dielectric and piezoelectric properties of 0.96Na_0.5K_0.5NbO₃-0.04SrTiO₃ (KNN-4ST) ceramics. As a result, the orthorhombic-tetragonal phase transition was observed at 2 mol% Li₂CO₃ modified KNN-4ST ceramics, whose TC, d33 and kp values are 328℃, 165pC/N and 0.33, respectively.

This study investigated crystal structures, microstructures, and electric-field-induced strain (EFIS) properties of Bibased lead-free ferroelectric/relaxor composites. Bi_1/2(Na_0.82K_0.18)_1/2TiO₃ (BNKT) as a ferroelectric material and 0.78Bi_1/2(Na_0.78K_0.22)_1/2TiO₃-0.02LaFeO₃ (BNKT2LF) as a relaxor material were synthesized using a conventional solid-state reaction method, and the resulting BNKT2LF powders were subjected to high-energy ball milling (HEBM) after calcination. As a result, HEBM proved a larger average grain size of sintered samples compared to conventional ball milling (CBM). In addition, the increased sintering time led to grain growth. Furthermore, HEBM treatment and sintering time demonstrated a significant effect on EFIS of BNKT/BNKT2LF composites. At 6 kV/mm, 0.35% of the maximum strain (S_max) was observed in the HEBM sample sintered for 12 h. The unipolar strain curves of CBM samples were almost linear, indicating almost no phase transitions, while HEBM samples displayed phase transitions at 5~6 kV/mm for all sintering time levels, showing the highest S_max/E_max value of 700 pm/V. These results indicated that HEBM treatment with a long sintering time might significantly enhance the electromechanical strain properties of BNT-based ceramics.

This study investigated microstructures, crystal structures, polarization, dielectric and electromechanical properties of 0.76Bi_1/2Na_1/2TiO₃-0.24SrTiO₃ (BNT-24ST)-based piezoceramcs by adding Li₂CO₃ and B₂O₃ (LB) as sintering aids for low-temperature sintering. All samples were successfully synthesized using conventional solid-state reaction method and sintered at 950, 1,000, 1,050, 1,100 and 1,175℃ for 2 hours. Without LB, specimens required sintering temperatures over 1,175℃ for sufficient densification, while the addition of 0.10-mol LB decreased the sintering temperatures down to 950℃. The average grain size and dielectric properties of BNT-24ST-10LB ceramics were enhanced with increasing sintering temperature. We found that the low-temperature sintered BNT-24ST piezoceramics by adding LB showed the d₃₃*value of 402 pm/V at 4 kV/mm after sintering at 1,050℃, which was better than that of high-temperature fired specimens sintered at 1,175℃ without LB (242 pm/V). We believe that the results of this study promise a candidate for low-cost multilayer ceramic actuator applications.

In this study, solder joints mixed with graphene-nanosheets (GNSs) were investigated for the manufacture of highly reliable electronic devices. In order to analyze the effect of adding GNSs, experiments were performed by adding various amounts of GNSs (0.01, 0.05, 0.1, 0.3, 0.5 wt%). To compare and analyze the properties of the solder joints to which GNSs were added, shear forces were measured, and cross-sectional observation was performed. The bonding strength of the solder joints containing 0.05% GNSs was the highest, and the bonding strength of the solder joints with higher GNSs contents did not increase. This is because, as the content of GNSs increases, the viscosity of the solder paste also increases; therefore, the solder paste detachability from the metal mask was lowered and a sufficient amount was not applied. In addition, due to the high content of GNSs, the fluidity of solder powder and paste decreased, resulting in defects in the shape of the solder joint. Therefore, the optimal GNSs content in this study was 0.05%, and studies for optimal viscosity should be continued.

This study investigated the structural, dielectric, ferroelectric, and strain properties of (0.98-x)Bi_1/2Na_1/2TiO₃- 0.02BiFeO_3-xSrTiO₃ (BNT-BF-100xST, x＝0.20, 0.22, 0.24, 0.26, and 0.28). All samples were successfully synthesized using the conventional solid-state reaction method and sintered at 1,175℃ for 2 h. The average grain size of the BNT-BF-100x ceramics decreased with increasing ST content. Furthermore, we observed that the ferroelectric- relaxor transition temperature (T_F-R) decreased with increasing ST content, which eventually vanished in the BNT-BF-24ST ceramics. The results indicated that a ferroelectric to relaxor phase transition could be induced by ST modification. Consequently, a large electromechanical strain of 633 pm/V at 4 kV/mm was observed for the BNT-BF-26ST ceramics. These results imply that our materials have the competitive advantage of larger strain under lower operating field conditions compared with other BNT-based lead-free piezoelectric ceramics. We expect that BNT-BF-ST lead-free piezoelectric ceramics are promising candidates as a novel ternary BNT-based system and can find potential applications in actuators.

This study investigated the low temperature sintering with various templates of Bi-based lead-free piezoelectric ceramics. The effects of using CuO-coated Na_0.5Bi_4.5Ti₄O₁₅ templates on the sintering behavior as well as the dielectric, ferroelectric, and piezoelectric properties of Bi_1/2(Na_0.78K_0.22)_1/2TiO₃ (BNKT) ceramics have been examined. In comparison with the specimens sintered with the Na_0.5Bi_4.5Ti₄O₁₅ templates without CuO coating, those sintered with the CuO-coated Na_0.5Bi_4.5Ti₄O₁₅ templates showed larger template sizes as well as a larger electric field induced strain (S_max/E_max) of 422 pm/V after sintering at temperatures as low as 975℃. These results are promising for low-cost multilayer ceramic actuator applications.

This study investigated the microstructure and piezoelectric properties of lead-free 0.74(Bi_1/2Na_1/2)TiO3-0.26SrTiO₃ (BNST26) piezoelectric ceramics sintered using a microwave furnace. For comparison, specimens were also prepared using a conventional furnace sintering (CFS). Average grain sizes of 2.4 μm and 3.2 μm were obtained in the sample sintered at 1,100℃ for 5 min using microwave sintering (MWS) and at 1,175℃ for 2 h using CFS, respectively. To quantify the changes in the microstructures and electrical properties according to the sintering conditions, the polarization hysteresis, bipolar and unipolar strain curves, and temperature dependence of permittivity were evaluated. As a result, it was determined that the Pmax (maximum polarization), Pr (remanent polarization) and Smax (maximum strain) values tend to increase with the average grain size. Based on these results, it is concluded that the MWS method can produce lead-free ceramics with superior performance in a relatively short time compared to the conventional CFS method.

Bonding properties of epoxy-containing solder joints were investigated by a high temperature aging test. Specimens were prepared by bonding an R3216 standard chip resistor to an OSP-finished PCB by a reflow process with two basic types of solder (SAC305 & Sn58Bi) pastes and two epoxy-solder (SAC305+epoxy & Sn58Bi+epoxy) pastes. In all epoxy solder joints, an epoxy fillet was formed in the hardened epoxy, lying around the outer edge of the solder joint, between the chip and the Cu pad. In order to analyze the bonding characteristics of solder joints at high temperatures, a high-temperature aging test at 150°C was carried out for 14 days (336 h). After aging, the intermetallic compound Cu₆Sn₅ was found to have formed in the solder joint on the Cu pad, and the shear stress on the conventional solder joint was reduced by a significant amount. The reason that the shear force did not decrease much, even though in epoxy solder, was thatbecause epoxy hardened at the outer edge of the supported solder joints. Using epoxy solder, strong bonding behavior can be ensured due to this resistance to shear force，even in metallurgical changes such as those where intermetallic compounds form at solder joints.

In this study, we investigated the optimum calcination temperature of lead-free 0.74(Bi_0.5Na_0.5)TiO₃-0.26SrTiO₃ (BNST) piezoelectric ceramics by analyzing the crystal structure, dielectric properties, and electric field-induced strain behavior. BNST ceramics prepared by conventional solid-state reaction methods at various calcination temperatures according to the industrial standard. All samples of BNST ceramics were subsequently sintered at 1,175℃ for 2 h. Crystal structure classification of the ceramics showed a single perovskite phase, with no second phase detectable for the samples calcined at 750℃ or higher. BNST samples calcined at 850℃ exhibited the most optimal values for itsand the common physical parameters of density = 5.518 g/㎤, ε = 1,871.837, tanδ = 0.047, and d₃₃^* = 874 pm/V.

We have studied the effects of Ag on the characteristics of Sn₄₃Bi₅₇Ag_x(wt%) lead-free solders for photovoltaic ribbon. Ag atoms in the solder formed an alloy phase of Ag₃Sn after reacting with some part of Sn atoms, while they did not react with Bi atoms, but decreased the mean size of Bi solid phase and the thickness of solder. When Ag atoms of 3.0 wt% was added to eutectic Sn₄₃Bi₅₇(wt%) solder, it showed the optimally useful results that the peel strength of photovoltaic ribbon greatly increased and the sheet resistance of the solder decreased. In the meanwhile, the eutectic Sn₄₃Bi₅₇(wt%) solder showed a low melting temperature of 138.9℃, and showed a very similar result regardless of the added amount of Ag atoms.

In this paper, piezoelectric ceramics with the composition of (Na0.525K0.4425Li0.0375)(Nb0.8975Sb0.065Ta0.0375)O3 + 0.3 wt% CoO + x CuO (0.005≤x≤0.025) (abbreviated to NKL-NST) were fabricated for ultrasonic sensor application. The effects of CuO addition and sintering on the microstructure and the piezoelectric properties of the NKL-NST ceramics were systematically studied. Excellent piezoelectric properties such as electromchanical coupling factor(kp) = 0.415, piezoelectric constant (d33) =166 pC/N and piezoelectric figure of merit d33*g33= 5.47 pm2/N were obtained from the 2.5 mol% CuO doped NKL-NST+0.3 wt%CoO ceramics sintered at 1,000℃ for 3 h.

We investigated the sintering behavior and piezoelectric properties of lead-free (K0.5Na0.5)NbO3 ceramics co-doped with excess 0.01 mol ZnO and x mol MnO2, where x was varied from 0 to 0.03. Excess MnO2 addition was found to retard the grain growth and densification during sintering. However, 0.005 mol MnO2 addition improved the piezoelectric properties of 0.01 mol ZnO added (K0.5Na0.5)NbO3 ceramics. The planar mode piezoelectric coupling coefficient, electromechanical quality factor, and piezoelectric constant d33 of 0.01 mol ZnO and 0.005 mol MnO2 added specimen were 0.40, 304, and 214 pC/N, respectively.

The bonding characteristics of MLCCs (multi layer ceramic capacitor, C1608) lead-free solder (SAC305) joints were evaluated through thermal shock test (-40℃~125℃, total 1,800 cycle). After the test, IMCs( intermetallic compounds) growth and cracks were verified, also shear strengths were measured for degradation of solder joints. In addition, The thermal stress distributions at solder joints were analyzed to compare the solder joints changes before and after according to thermal shock test by FEA (finite elements analysis). We considered the effects of IMCs growth at solder joints. As results, the bonding characteristics degradation was occurred according to initial crack, crack propagations and thermal stress concentration at solder-IMCs interface, when the IMCs grown to solder inside.

In this paper, in order to develop excellent Pb-free composition ceramics for ultrasonic sensor. The SnO2-doped (Na0.525K0.443Li0.037)(Nb0.883Sb0.08Ta0.037)O3)(abbreviated as NKL-NST) ceramics have been synthesized using the ordinary solid state reaction method. The effect of SnO2-doping on their dielectric and piezoelectric properties was investigated. The ceramics doped with 0 wt% SnO2 have the optimum values of piezoelectric constant(d33), piezoelectric figure of merit(d33·g33), planar piezoelectric coupling coefficient(kp) and density : d33= 195[pC/N], d33·g33=5.62 pm2/N.kp= 0.40, density= 4.436[g/cm3]. suitable for duplex ultrasonic sensor application.

In this study, we developed a lead-free P_{2}`O_{5}`-V_{2}O_{5}-ZnO glass frit for sealing OLED using laser irradiation. The frit satisfied the characteristics required for laser sealing such as low glass transition temperature, low coefficient of thermal expansion (CTE), high water-resistance, and high absorption at the wavelength of the laser beam. Ceramic fillers were added to the glass frit in order to further reduce and match its CTE with that of the commercial glass substrate. The addition of Zirconium Tungsten Phosphate (ZWP) to the frit yielded the most desirable results, reducing the CTE to 45.4×10^{-7}/℃, which is very close to that of the glass substrate (44.0×10^{-7}/℃). Successful formation of a solid sealing layer was observed by optical and scanning electron microscopy.

In this paper, in order to develop outstanding Pb-free piezoelectric composition ceramics, the (Na0.525K0.443Li0.037)(Nb0.883Sb0.08Ta0.037)O3 + 0.3 wt%Bi2O3 + 0.4 wt%Fe2O3 + x wt%CuO (x= 0∼0.8 wt%)(abbreviated as NKL-NST) lead-free piezoelectric ceramics have been synthesized using the ordinary solid state reaction method. The effects of CuO-doping on the structure and electrical properties of the NKL-NST ceramics were systematically studied. The results show that the ceramics exhibit a pure perovskite structure with orthorhombic phase at room temperature, and secondary phase was found in the ceramics. The 0.4 wt%CuO added ceramics sintered at 950℃ showed the optimum properties of piezoelectric constant(d33), planar piezoelectric coupling coefficient(kp) and mechanical quality factor(Qm) : d33= 213 [pC/N], kp= 0.43, Qm= 423,respectively.

Bi0.5+x(Na0.78K0.22)0.5-3xTiO3 ceramics with an excess Bi3+ and a deficiency of Na+ and K+ were synthesized by a conventional solid state reaction method. The structure and morphology ofBi0.5+x(Na0.78K0.22)0.5-3xTiO3 ceramics were characterized by X-ray diffraction and field emission scanning electron microscopy. The electric polarization and mechanical strain induced by external electric field, and the temperature dependence of dielectric constant were investigated. These results demonstrated that anergodic relax or phase can be induced by controls of the mole ratio of Bi3+, Na+ and K+. A phase boundary between non-ergodic and ergodic relaxor phases can be observed at ambient temperature. Theergodic relaxor phase can be transferred to the ferroelectric phase by application of the electric field. The stability of the induced ferroelectric phases strongly depends on the mole ratio of Bi3+, Na+ and K+. The maximum strain of 0.31% was observed in Bi0.51(Na0.78K0.22)0.47TiO3 ceramics sintered at 1,150℃ for 2 h.

The 0.99Bi0.5(Na0.78K0.22)0.5TiO3?0.01LaAlO3, 0.01LaMnO3 or 0.01LaFeO3 (0.99BNKT?0.01LA,0.01LM or 0.01LF) ceramics were prepared by a conventional mixed mothod. The structure andmorphology of the lead free ceramics were characterized by XRD (X-ray diffraction) and FE-SEM (fieldemission scanning electron microscopy). XRD results indicated that the BNKT ceramics modified by LA,LM or LF induced a transition from a ferroelectric tetragonal to a non-polar pseudo-cubic phase, leadingto decrease in the remnant polarization (Pr) and coercive field (Ec) in the P-E hysterisis loops. Theeffects of the BNKT ceramics modified by La-based ABO3 pervskite structure on the electric-fieldinduced strain were investigated, and the largest normalized unipolar strain (Smax/Emax) was found inBNKT-0.01LF ceramic.

(Na0.525K0.4425Li0.0375)(Nb0.9975Sb0.065Ta0.0375)O3 + 0.3 wt%CoO ceramics were fabricated as a functionof CuO addition by traditional solid state sintering process in order to develop excellent lead-freepiezoelectric ceramics composition. The addition of CuO in the LNKNTS composition ceramics caneffectively enhance the densification of the ceramics, resulting in the oxygen vacancies as hardeningeffect. The excellent piezoelectric properties of electromechanical coupling factor(kP) of 0.378, piezoelectricconstant(d33) of 152 pC/N were obtained from the 1.0 mol% CuO doped LNKNTS ceramics sintered at1,020℃ for 3 h.

n this paper, in order to develop outstanding Pb-free composition ceramics, the Fe2O3-doped(Na0.525K0.443Li0.037)(Nb0.883Sb0.08 Ta0.037)O3 + 0.3 wt% Bi2O3 + x wt% Fe2O3 (x= 0∼1.0 wt%)(abbreviated as NKL-NST) lead-free piezoelectric ceramics have been synthesized using the ordinary solid state reaction method. The effect of Fe2O3-doping on their microstructure and electrical properties were investigated. XRD diffraction pattern studies confirm that Fe2O3 completely diffused into the NKL-NSTlattice to form a new stable soild solution with Fe3+ entering the Nb5+, Sb5+ and Ta5+ of B-site. And, phase structure of all the ceramics exhibited pure perovskite phase and no secondary phase was found in the ceramics. The ceramics doped with 0.6 wt% Fe2O3 have the optimum values of piezoelectric constant(d33), planar piezoelectric coupling coefficient(kp) and mechanical quality factor(Qm) : d33= 233[pC/N], kp= 0.44, Qm= 95. These results indicate that the (Na0.525K0.443Li0.037)(Nb0.883Sb0.08Ta0.037)O3 +0.3 wt%Bi2O3 + 0.6 wt% Fe2O3 ceramic is a promising candidate for lead-free piezoelectric ceramics.

MnO2-doped 0.985[Li0.04(Na0.545K0.46)0.96(Nb0.81Ta0.15Sb0.04)]O3+0.015KNbO3(0.985LNKNTS+0.015KNbO3)lead-free ceramics were fabricated by conventional solid state method to develop excellent dielectric andpiezoelectric properties. The result of X-ray diffraction patterns obviously indicated that all of thespecimen has pure perovskite structure without secondary phase. In addition, orthorhombic phase andcoexistance region of orthorhombic-tetragonal phase (MPB) were observed with amount of MnO2. Theoptimal values of ρ=4.70 g/cm3, d33=238 pC/N, kP=0.46, Qm=121, εr=849, and TC=225℃ were obtained at0.01 mol% MnO2 doped 0.985LNKNTS+0.015KNbO3 ceramics sintered at 990℃ for 5 h, respectively. Hence, it was indicated that the suitable amount of MnO2 could improve the electrical properties of0.985[Li0.04(Na0.545K0.46)0.96](Nb0.81Ta0.15Sb0.04)]O3+0.015KNbO3 ceramics.

We investigated the effect of excess CuO on the sintering behavior, ferroelectric, andpiezoelectric properties of lead-free Bi0.5(Na0.82K0.18)0.5TiO3 (BNKT) ceramics. The addition of excess CuOwas found to greatly contribute to the densification and grain growth, however, excess CuO over 3 mol%was precipitated at grain boundaries after sintering. BNKT with 1∼2 mol% CuO in excess sintered at975℃ showed piezoelectric properties comparable to those of unmodified BNKT sintered at 1,175℃. These results seem meaningful for its application to low cost multilayer actuators (MLAs) becauselow firing ceramics make it possible to apply less expensive base metals to the inner electrode ofMLAs.

(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3+0.04wt% CeO2 lead-free ceramics were prepared by conventional oxide-mixed method and the effect of sintering temperature on microstructure, dielecrric and piezoelectric properties were investigated. Improved piezoelectric properties have been observed at 1,400℃ sintering temperature which show the optimal electrical properties, kp~0.412, d33~316 Pc/N, Qm~144, ~3,345 and Tc~85℃. These results show that the sintering temperature plays an important role in piezoelectric properties.

In this study, (Na0.525K0.443Li0.037)(Nb0.883Sb0.08Ta0.037)O3 + 0.10 wt%Bi2O3 + 0.35 wt%B2O3 ceramics were prepared by conventional soild-state sintering process. The specimens were sintered at temperature range from 1,060℃ to 1,100℃. XRD (X-ray diffractron), SEM (scanning electron microscope) were used to analyze the crystal structure and microstructural sproperties of specimens. And also, TO-T, TC were observed by the mesurement of temperature dependence of dielectric constant. Excellect physical properties of the piezoelectric constant d33= 170 pC/N, electromechanical coupling factor kp= 0.312, Tc= 315℃ were obtained, respectively, from the specimen sintered at 1,080℃.

(Na,K)NbO3-based piezoelectric ceramics were synthesized by a liquid phase sintering method with a selected glass frit. The effects of the content of the glass frit and the sintering temperature on the microstructure and the electrical properties of the samples were investigated. With the 0.1 wt% of glass frit content, (Na0.52K0.44Li0.06)(Nb0.84Ta0.10Sb0.06)O3 (NKL-NTS) ceramics showed the maximum values of the relative density (99.1%) and the electro-mechanical coupling factor (kp: 0.32) at the sintering temperature of 1,050℃. It might mean that a liquid phase sintering with a suitable glass frit having the lower flow temperature could improve the relative density and the piezoelectric properties.

In this paper, the + 0.005KNhO: ÷ xwt9`o le02 lead-free piezoelectric ceramics for energy harvesting devices were fabricated by the conventiona] mixed oxide method. The microstructure, dielectric, and piezoelectric properties were investigated as a function of the Te09 addition. All the specimens showed an orthorhombic phase structure. At the composition ceramics doped with 0.1 wt%Te02, the optimum values of da 212 pC/N, d33`g33= 9.54 pm2/N, and kp= 0.448 were obtained, respectively. The results indicate that the composition ceramics is a promising candidate for energy harvesting devices applications.

In this paper, the 0.95(Na_0.5K_0.5)_0.04[(Nb_0.8Ta_0,20)_0.994Co_0.015]O_3(abbreviated as NKNT) + 0.05KNbO_3 lead-free piezoelectric ceramics were synthesized by the conventional mixed oxide method route with normal sintering. And also, the effects of calcination temperature on the microstructure, dielectric properties, and piezoelectric properties were investigated. A polymorphic phase transition(PPT) between orthorhombic and tetragonal phases was observed in specimens calcined at 810℃∼850℃. The ceramics calcined at 830℃ showed excellent piezoelectric properties: d_33= 179 pC/N, k_p= 0.384, Q_m= 79.73). These results indicate that the ceramic is a promising candidate material for lead-free piezoelectric ceramics.