Ternary Ceramics Research Articles

Phase structure, microstructure and electrical properties of PCNS–PZ–PT ternary ceramics near the morphotropic phase boundary

In the present study, (0.54 − x)Pb(Cr1/5,Ni1/5,Sb3/5)O3-0.46PbZrO3-xPbTiO3 ceramic powders were synthesized by the conventional solid-state reaction process (where x = 0.42, 0.44, 0.46, 0.48 and 0.50). The obtained samples have been characterized using different techniques such as X-ray Diffraction (XRD) which reveals that the samples consist of a mixture of tetragonal and rhombohedral phases (morphotropic phase boundary MPB) in the range of 0.46 ≤ x ≤ 0.48, scanning electron microscopy (SEM) which shows an increase of the average grain size in the morphotropic phase boundary, dielectric measurements and Raman spectroscopy have been performed to get more insights into the effects of titanium dopant (Ti) content on the properties of PCNS–PZ–PT ceramics near the morphotropic phase boundary (MPB). It was found that the ceramic sintered at 1180 °C with Ti = 46% achieves excellent dielectric properties (er = 17,641.58, tan δ = 0.120 and Tc = 576 K).

High dielectric permittivity of BiFeO3–SrTiO3–CaTiO3 ternary solid solution ceramics

xCaTiO3-(0.8-x)SrTiO3-0.2BiFeO3 (x = 0, 0.3, 0.5, 0.7) ternary solid solution ceramics were prepared by a conventional high temperature sintering method. The structural and electrical properties of these ceramics were studied comprehensively. 0.3CaTiO3-0.5SrTiO3-0.2BiFeO3 ceramics show large dielectric permittivity and small variation over a broad temperature range, making it a potential candidate for high-temperature electronic applications. The origin of the large dielectric permittivity is discussed based on the contributions of both A-site and B-site cations on the polarizability of the system. The multiple cations induced local structural heterogeneity and/or random field is proposed as the reason for the thermal stability of dielectric permittivity.

Understanding the oxidation behavior of Ta–Hf–C ternary ceramics at high temperature

For high-temperature applications, poor oxidation performance of Ta–Hf–C ternary ceramics is an important life-limiting factor. In this work, the oxidation mechanisms of various compositions of Ta–Hf–C ternary ceramics are studied systematically at 1400–1600 °C in air under isothermal conditions for the first time. The oxidation process is demonstrated to be composition dependent: 1TaC–1HfC and 1TaC–3HfC exhibit considerably improved oxidation resistance compared to TaC and HfC individual carbides along with 4TaC–1HfC and 1TaC–4HfC ternary ceramics. The results obtained herein should pave the way to design advanced oxidation-resistant Ta–Hf–C ternary ceramics for high-temperature applications.

Synthesis and Characterization of Meltable and Soluble Reticulating Polysilazane Modified via Melamine Toward SiCN Ternary Ceramics

The molecular structure of polymer has a great influence on the physical and chemical properties of polysilazane and the properties of ceramics pyrolyzed from the polysilazane. The polysilazane with reticulating molecular structure has good performance generally. The performance of the precursor can be effectively improved by reasonable molecular structure design and control of the synthesis process. In this paper, a reticulating polysilazane PSZ-M with outstanding meltability and solubility were synthesized via an aminolysis reaction between dichloromethylsilane (DCMS) and hexamethyldisilazane (HMDZ), and using the melamine as additive. The properties and the ceramization process of PSZ-M, as well as the molecular structure and properties of derived SiCN ceramic, were well studied. The melamine can be introduced via the dehydrogenation reaction between N–H and Si–H. The ceramics yield was enhanced to 63.18% at 900 °C after the introduction of melamine. The SiCN ceramics derived from the PSZ-M can remain amorphous when pyrolyzed below 1400 °C, the crystal phase of SiC, SiN4 were detected for 1500 °C treated samples. The using of melamine as an additive to synthesis polysilazanes has led to the development of a convenient approach for constructing polysilazanes with reticulating structure and ideal performance, which supports a strategy for the structure design of preceramic polymers.

Crystal structure evolution and luminescence property of Ce3+-doped Y2O3-Al2O3-Sc2O3 ternary ceramics

Ce3+-doped Y2O3-Al2O3-Sc2O3 ternary ceramics with varying Sc2O3 were prepared via solid-state-reactive method. Their constitutions, crystal structures, microstructures and luminescence properties were thoroughly investigated by powder X-ray diffraction, 45Sc and 27Al solid-state nuclear magnetic resonance (NMR), scanning electron microscope (SEM) as well as photoluminescence (PL) characterizations. Single-phased YSAG transparent ceramics with garnet structure and homogeneous microstructures can be obtained. The NMR results suggest that partial [AlO6] octahedrons are converted into [AlO4] tetrahedrons with increased Sc3+. Partial Sc3+ occupies the remaining octahedral sites, the other Sc3+ occupies the dodecahedral sites. The luminescence spectra of the as-prepared ceramics show broadened emission bands with excessive Sc3+ incorporation. More significantly, the solubility of Ce3+ in garnet ceramics extensively increases due to the incorporation of Sc3+, leading to a considerable red-shift and broadening of emission spectra with little luminescence decline, indicating that the new ceramic phosphors are promising for white-light illumination with improved color rendering index.

Study on piezoelectric, dielectric and dispersive phase transition of BaTiO3–BaZrO3–CaTiO3 ceramics

The dielectric, piezoelectric properties and dispersive ferroelectric phase transitions of (0.84 − x) BaTiO3–0.16CaTiO3–xBaZrO3 ternary ceramics were investigated in this manuscript. The study found that the optimum BaZrO3 doping amount was 0.1 mol%. Compared to the binary system, the ternary system has a denser microstructure and a more uniform grain size, and more excellent electrical properties. The influence mechanism of BaZrO3 doping on the system was explained in detail by lattice theory and domain theory.

Phase evolution and relaxor behavior of BiScO3–PbTiO3–0.05Pb(Yb1/2Nb1/2)O3 ternary ceramics

High-temperature piezoelectric ceramics (0.95 − x)BiScO3–xPbTiO3–0.05Pb(Yb1/2Nb1/2)O3 (BS–xPT–PYN, x = 0.56–0.64) were prepared by a conventional solid-state reaction method. X-ray diffraction and Raman spectra demonstrated that the ceramics convert from monoclinic phase (x ≤ 0.58) to tetragonal phase (0.62 ≤ x ≤ 0.64). A phase coexistence of monoclinic and tetragonal in the vicinity of the MPB (x = 0.60) enhances the ferroelectric polarizability by a dynamical conversion between two energy-degenerate states with d33 = 392 pC/N, kp = 53.3% and Pr = 38.8 μC/cm2 and the operation temperature up to ~ 400 °C. Relaxor behaviors, which following the V–F law, are presented in this system and their dipole activation energy decrease for higher component x. The phase fraction versus temperature of the MPB (x = 0.60) was investigated by an in situ XRD, which gives an insight into the origin of the high-temperature piezoelectricity.

Structure and enhanced piezoelectric performance of BiScO3-PbTiO3-Pb(Ni1/3Nb2/3)O3 ternary high temperature piezoelectric ceramics

BiScO3-PbTiO3 based solid solutions are the most promising candidates in high temperature piezoelectric application field. In this research, (1-x-y)BiScO3-xPbTiO3-yPb(Ni1/3Nb2/3)O3 (BS-xPT-yPNN) ternary high temperature piezoelectric ceramics have been prepared by the traditional solid-state reaction methods and investigated in detail. X-Ray diffraction analysis shows that the system has a pure perovskite structure and the morphotropic phase boundary (MPB) region shifts to the low PT region with the increasing PNN end member. The room temperature phase diagram has been drawn to predict the MPB region and search for the optimal electrical properties of the BS-xPT-yPNN ternary solid solutions. The dielectric temperature spectra present typical diffuse phase transition characteristic caused by the production of chemical heterogeneities with the introduction of PNN. For the BS-xPT-0.025PNN system, the optimal properties of the piezoelectric coefficient d33 522 pC/N, planar electromechanical coupling factor kp 59.6%, remnant polarization Pr 39.2 μC/cm2, and the Curie temperature Tc 400 °C are obtained for the BS-0.61PT-0.025PNN composition. Furthermore, the piezoelectric performance declines a little to 495 pC/N and 59% of the BS-0.60PT-0.05PNN composition with the increase of PNN content, which is also equivalent to that of the unmodified BS-PT and other modified BS-PT such as the BS-PT-PZN system. All these properties reveal that the BS-xPT-yPNN ceramics constitute a new family of high performance high temperatures piezoelectric materials.

Effect of scanning speed on the solidification process of Al2O3/GdAlO3/ZrO2 eutectic ceramics in a single track by selective laser melting

Abstract Al2O3/GdAlO3/ZrO2 ternary eutectic ceramics with fine microstructure were directly fabricated from mixed pure ceramic powders by selective laser melting. The specimen forming quality, molten pool morphology and microstructure characteristic were investigated as functions of scanning speed. Solidification defects such as cracks and pores were effectively suppressed when the scanning speed was 12 mm/min. The relative density of the as-solidified eutectic specimens decreased from 98.7% to 95.7% with increasing the scanning speed up to 48 mm/min. The melting in this study was governed by conduction mode, leading to a decrease tendency of both melting width and depth with the increase of the scanning speed. Different from ordinary cognition, the eutectic spacing in top zone of the molten pool first decreased and then increased with increasing the scanning speed from 6 mm/min to 48 mm/min. The transition point appeared at 12 mm/min, where the dominant factor affecting the solidification rate changed from the scanning speed to the value of the angle between microstructure growth direction and laser scanning direction.

Investigation of enhanced performance in BF-xPT-0.05BZ ternary ceramics for high temperature applications

Abstract (0.95-x)BiFeO3-xPbTiO3-0.05BaZrO3 (BF-xPT-0.05BZ) ternary ceramics were synthesized by the solid-state reaction method, which present a perovskite structure without detectable second phase. BF-0.32PT-0.05BZ ceramics display the dominant rhombohedral structure with a small amount of tetragonal phase, revealing the characteristics of morphotropic phase boundary (MPB). The well-densified ceramics possess the average grain size of 8–15 μm with different PT contents. The ferroelectric-paraelectric phase transition of BF-xPT-0.05BZ ceramics shows the characteristic of the first-order transition, which occurs at around 550 °C. It is noticeable that BF-0.32PT-0.05BZ ceramics exhibit the giant remnant polarization of 60 μC/cm2 under the field of 175 kV/cm. Moreover, BF-0.32PT-0.05BZ ceramics show the highest piezoelectric constant d33 of 105 pC/N and Qm of 501. The depolarization temperatures of BF-xPT-0.05BZ ceramics are much close to their Curie temperature TC, proving the extensive prospect for high temperature piezoelectric applications.

Nanostructured Al2O3-YAG-ZrO2 ternary eutectic components prepared by laser engineered net shaping

The present work proposed a novel 3D printing approach for fabricating ternary eutectic ceramics (Al2O3-YAG-ZrO2, or AYZ in short) using laser engineered net shaping (LENS) technique. Highly dense (≥98%) thin wall components with refined eutectic microstructures were successfully fabricated. The as-fabricated ceramic eutectics mainly consist of cellular eutectics with three phases interpenetrated. In each deposited layer, the solidified microstructure changes from planar to cellular along building direction. The evolution of characteristic dimension of microstructure can be well interpreted using Jackson-Hunt relationship. Irregular interpenetrating to regular fibrous eutectic structure transition occurs at boundary region of LENSed specimens, primarily due to much higher solidification rate. The texture of <0001>Al2O3//<001>YAG//<001>ZrO2 is recognized at the interior region of LENSed eutectic part along building direction, but gradually tilts from central to edge due to change of cellular growth direction. The LENSed AYZ samples exhibit almost isotropic property, and have mechanical performances comparable to those fabricated using conventional direction solidification methods.

Structure, electrical properties and temperature stability of PIN–PZN–PT piezoelectric ceramics with morphotropic phase boundary compositions

A series of Pb(In[Formula: see text]Nb[Formula: see text]O3–Pb(Zn[Formula: see text]Nb[Formula: see text]O3–PbTiO3 (PIN–PZN–PT) ternary piezoelectric ceramics with compositions at the morphotropic phase boundary (MPB) were prepared. The phase structure, microstructure, electrical properties and temperature stability of PIN–PZN–PT ceramics were investigated systematically. The structural analysis indicated that an MPB phase consisting of rhombohedral and tetragonal phases was formed in all ceramics. For the selected compositions, dielectric measurements demonstrated that the Curie temperature [Formula: see text] changed from 237∘C to 295∘C and showed a strong trend of compositional dependence. All the samples showed good piezoelectic properties. Particularly, the 0.35PIN–0.40PZN–0.25PT sample has the optimum piezoelectric properties, the piezoelectric coefficient [Formula: see text] is 589 pC/N, the electromechanical coupling factors [Formula: see text] and [Formula: see text] are 59% and 49%, respectively. Compared with PZN–PT and PMN–PT ferroelectric crystals, the superior limit of usage temperature of PIN–PZN–PT ceramics was achieved around 230∘C by thermal depoling method. These results make PIN–PZN–PT ceramics a promising material to meet the practical demands of higher temperature and larger electric field operating ranges.

Infrared Transparency and Conductivity of Amorphous Ternary Ceramic Thin Films

In this paper, using polycrystalline Ti3SiC2 powder as target, for the first time, amorphous ternary ceramic (a-TSC) thin films are successfully fabricated on quartz and glass substrates at room temperature by direct-current (DC) sputtering. The microstructural and optoelectronic properties of the a-TSC thin films are investigated by means of XRD, Raman, EDS, four-point probe system and Vis-NIR spectrometer, respectively. It is found that despite of amorphous structure and having not so good conductivity compared with Ti3SiC2, the a-TSC thin films still have enough conductivity. Furthermore, compared with ITO, FTO and AZO thin films, the transmittance of a-TSC thin films is much higher in infrared region regardless of the film thickness. It is suggested for a-TSC thin films that the film thickness should be controlled less than 150nm in order to obtain a higher transparency with an appropriate conductivity. It is believed that a-TSC thin film will find its way to be applied in optoelectronic devices in the near future.

Growth rate effect on colony formation in directional solidification of Al2O3/YAG/ZrO2

AbstractMechanical properties of Al2O3/Y3Al5O12/ZrO2 ternary eutectic ceramics are strongly affected by structural defects as pores or colonies. Experimental investigation of the microstructure of this ternary composite indicates that the colonies are generally observed when the solidification occurs at high rates. In this work, the influence of the growth rate on the solid‐liquid interface shape and formation of colonies in directional solidification of Al2O3/Y3Al5O12/ZrO2 by Bridgman, Edge‐defined Film‐fed Growth (EFG), and Czochralski (Cz) methods is numerically and experimentally investigated. Numerical modeling of the Bridgman growth process shows large curvatures of the solid‐liquid interface when the pulling rate is increased up to 80 mm/h. The ingots solidified at rates between 5 and 80 mm/h exhibit colony type microstructure. The analysis of EFG growth of ceramic ribbons reveals less curved solid‐liquid interfaces in this system. Numerical modeling shows significant increase in the interface curvature with increasing pulling rate. The microstructure of ribbons grown at pulling rates between 6 and 12 mm/h exhibits colonies only for the ingots solidified at higher rate. Simulations carried out for Czochralski growth process show that the solidification front is almost plane in this system. These results are in agreement with experimental observations showing good structural quality of Cz grown crystals with a flat solid‐liquid interface. Finally it is concluded that formation of colonies in directional solidification of this ternary eutectic composite is linked to large curvatures of the growth interface.

Large electromechanical strain and electrostrictive effect in (1 − x)(Bi0.5Na0.5TiO3–SrTiO3)–xLiNbO3 ternary lead-free piezoelectric ceramics

Lead-free (1 − x)(0.8Bi0.5Na0.5TiO3–0.2SrTiO3)–xLiNbO3 (BNST–xLN, x = 0–0.08) piezoelectric ceramics were fabricated by a solid-state sintered technology. The effects of LN-doping on the structural and electrical properties of the BNST–xLN system were systematically investigated. The results of Raman spectroscopy revealed that the substitution of LN softens the phonon vibrations in the BNST–xLN system, in accordance with the remarkable reduction in the phase transition temperature (TF−R), remnant polarization (Pr), negative strain (Sneg) and piezoelectric coefficient (d33). However, the degradation of the long-range ferroelectric orders was accompanied by a significant increase in the electric field–induced strain response. At x = 0.04, a maximum unipolar strain of ~ 0.36% with a corresponding normalized strain (Smax/Emax) of ~ 600 pm/V was obtained at room temperature, which should be mainly ascribed to the reversibly electric field-induced phase transition between the ergodic relaxor and ferroelectric phases due to their comparable free energies in the two-phase coexistence region. Moreover, it was also found that the BNST–xLN system processes predominant electrostrictive behaviors with relatively high electrostrictive coefficient (Q33) and excellent temperature stability when the field-induced phase transition cannot be trigged by the applied electric field, as evidenced by a fact that the Q33 value of BNST–0.08LN ceramic keeps almost constant as high as ~ 0.028 m4/C2 in the temperature range from room temperature to 120 °C.

Structure and Electrical Properties of Morphotropic Phase Boundary (Na1/2Bi1/2)TiO3‐PbTiO3‐Bi(Mg1/2Ti1/2)O3 Ternary System

The xBi(Mg0.5Ti0.5)O3‐(0.86−x)(Bi0.5Na0.5)TiO3‐0.14PbTiO3 (xBMT‐(0.86−x)NBT‐0.14PT) (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20) ternary solid solution ceramics are fabricated using a conventional solid‐state reaction method. The effect of tetragonality of tetragonal phase and local structure on the dielectric, ferroelectric, and piezoelectric properties is systematically investigated for the compositions near morphotropic phase boundary (MPB). The curves ϵ(T) for unpoled x = 0.02, 0.04, 0.06, 0.08 samples exhibit three dielectric anomalies upon heating. With increasing the BMT content, c/a ratio of the tetragonal phase slightly decreases, and the structure turns into pseudocubic phase. The largest values of d33 and Pr are obtained for x = 0.10 sample, being about twice as much as that of the 86NBT‐14PT sample, which can be attributed to the emergence of the nanostructure.

Effects of substitution element on physical properties of BiFeO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;-BaTiO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; ferroelectric ceramics driven by data-mining oxide perovskites

Data-mining from reliable extant data on basis of material informatics can lead to unveil those hidden qualitative and quantitative rules and make predictions of new materials faster and cheaper, which would reduce human synthesis effort than traditional trial-and-error way. In contrast to traditional scenario of material research initiated by scientists intuition and in a chain of synthesis-observation-analyses of mechanism, modern material research will change into productions and applications of data provoked by data science paradigm, while the present bottleneck of material informatics is still limited by the number of data. In the field of functional materials of ferroelectric piezoceramics, there are two ongoing trends of developing lead-free piezoceramics with thermal aging stability and high temperature piezoceramics with higher response for applications like in Internet-of-Things (IoT) and smart systems. Recent years, data-mining on oxide perovskites and designing new perovskite-type high temperature piezoceramics have been carried out and progresses were firstly reviewed in a short. Based on those quantitative relationships and rules data-mined out previously, various kinds of substitution elements for BiFeO3-BaTiO3(BF- x BT) solid solution ferroelectrics were proposed on basis of the mass and cation size features of atom and their effects on ferroelectric phase transition temperature, dielectric and piezoelectric properties observed experimentally. The compositions were tentatively chosen near the rhombohedral-pseudocubic structural phase boundary in order to check predominant contribution from substitution element. Among those elements of Al, Sc, Zn1/2Ti1/2 substitution for Fe and Bi1/2Nb1/2, Al1/2Nb1/2, Zn1/3Nb2/3, Zr, Sn for Ti, it was demonstrated experimentally that Bi(Zn1/2Ti1/2)O3 (BZT) exhibits a very promising effect in the BF- x BT system to obtain piezoceramics prepared using conventional solid state electroceramic processing with robust insulating and low dielectric loss properties fulfilled for the requirements of engineering applications. For those low dielectric loss BF- x BT- y BZT ternary solid solution ceramics, their ferroelectric Curie temperature ( T C) follows a quadratic polynomial relation of T C ( μ ) = a + b μ + c μ 2 and reduced mass of unit cell ( μ ) is a good descriptor to represent BF- x BT and BF- x BT- y BZT solid solution perovskite numerically. Full poling for piezoelectricity was obtained in Mn-doped BF- x BT- y BZT ( x ≤0.32, y 0.05) ceramics. So far, two ferroelectric piezoceramic materials were selected out: one is Mn-doped 0.74BF-0.22BT-0.04BZT exhibiting piezoelectric constant d 33~75 pC/N, dielectric constant e 33T/ e 0~260, dielectric loss tan δ ~0.01, thickness electromechanical coupling factor kt ~0.42, radial electromechanical coupling factor kp ~0.29 and T C~630°C, four times piezoresponse of commercial K-15 Aurivillius-structured bismuth titanate ceramics; another is Mn-doped 0.69BF-0.27BT-0.04BZT exhibiting d 33~145 pC/N, e 33T/ e 0~570, tan δ ~0.03, kt ~0.41, kp ~0.33, T C~510°C, 50% beyond K-81 tungsten-bronze-structured lead metaniobate ceramics. Similar to PbZr1- x Ti x O3(PZT) system, BF-BT-BZT system exhibits a structural phase boundary and thus their piezoelectric performance and thermal stability could be modified in a wide range through adjusting composition and doping. At this point, it is time performing systematical characterizations on BF-BZT-BT perovskite-type piezoceramics for high temperature engineering application testing. Based on the correlation between d 33 and e 33 for piezoceramics data-mined out previously, how to reduce synthesis effort for designing new materials was also argued using bad dielectric data of those high dielectric loss samples. Our essay demonstrates data-mining driven designing based on material informatics sure able to reduce time-to-insight and human effort on synthesis, accelerating new materials discovery and deployment.

Influence of BaZrO3 additive on the energy-storage properties of 0.775Na0.5Bi0.5TiO3-0.225BaSnO3 relaxor ferroelectrics

Dense (1-x)(0.775NBT-0.225BSN)-xBZ ternary ceramics were fabricated by solid state methods and their dielectric and ferroelectric properties were systematically investigated. XRD and Raman analysis indicate that the structure complexity and phase diffusion were enhanced in 0.775NBT-0.225BSN relaxor system with BZ addition. With increasing the contents of BZ, average grain size greatly decreases. Dielectric study shows that dispersive relaxor-like behavior was beginning to convert to diffusive phase transition when x ≥ 0.2. Along with increasing the BZ contents, the slop of P-E loops and the energy-loss can gradually decrease. When x = 0.2, both a high Wd of 2.08 J/cm3 and η of 88.8% were achieved, due to the slimer P-E loops, the high Pm (∼20 μC/cm2) and Eb (245 kV/cm). As a result, the ternary ceramics system may be a good candidate for energy-storage ceramics of NBT-based materials.

Competitive growth of Al2O3/YAG/ZrO2 eutectic ceramics during directional solidification: Effect of interfacial energy

AbstractThe microstructure evolution and growth behavior of the Al2O3/Y3Al5O12(YAG)/ZrO2 ternary eutectic ceramics during directional solidification were well investigated. During directional solidification of the Al2O3/YAG/ZrO2 ternary eutectic ceramics, {} Al2O3 paralleled with {001}ZrO2 while they did not parallel with {001}YAG at the same time in the competitive growth stage. All of the interfaces parallel to each other finally. The area percentage of the Al2O3/ZrO2 and YAG/ZrO2 interfaces are 40.4 ± 0.2% and 30.8 ± 0.1%, respectively, higher than that of the Al2O3/YAG (28.8 ± 0.2%). The content of Al2O3 and YAG phases are 39.9% and 41.1%, respectively, almost double of that of ZrO2. The interfaces of Al2O3/ZrO2 and YAG/ZrO2 are shorter and more dispersed than that of the Al2O3/YAG. It was found that the interfacial energy of Al2O3/ZrO2 and YAG/ZrO2 interfaces are lower than that of Al2O3/YAG. It can be concluded that interfacial energy plays a decisive role in affecting the crystallographic orientation and interfaces distribution in the Al2O3/YAG/ZrO2 eutectic since the interfaces of Al2O3/ZrO2 and YAG/ZrO2 with lower interfacial energy can be formed more easily during directional solidification. Therefore, the contents of Al2O3/ZrO2 and YAG/ZrO2 interfaces are higher. This study can provide theoretical guidance for interface design of multi‐phase materials.

Role of BiScO3 in phase structure and electrical properties of potassium sodium niobate ternary materials

In this work, we mainly studied the effects of BiScO3 contents on the phase structure and electrical properties of lead-free (K,Na)NbO3-based ternary ceramics, and the material system of (0.97-x)K0.40Na0.60NbO3-xBiScO3 -0.03Bi0.5(Na0.6K0.3Li0.1)0.5HfO3 was prepared by the normal sintering method. The rhombohedral-tetragonal (R-T) phase boundary could be tuned in the ceramics by controlling BiScO3 contents. When the compositions approach the R-T phase boundary, the ceramics possess the enhancement of dielectric, ferroelectric and piezoelectric properties. The ceramics with x = 1.2% exhibited an excellent electrical behavior of d33 = 362 pC/N, kp∼0.42, Pr∼19.9 μC/cm2, εr∼1671, and tan δ∼0.02, which is assigned to the involvement of R-T phase boundary. Moreover, a high Curie temperature (TC) of ∼315 °C can be maintained even if the BiScO3 contents increase because of the addition of both BiScO3 and Li. As a result, the ceramics with x = 1.2% had both a large d33 and a high TC, showing that such a lead-free piezoelectric ternary system is suitable to the high-temperature applications.