Direction Of Spontaneous Polarization Research Articles

Boosting the piezocatalytic performance of BaTiO3-based materials via phase boundary and defect co-engineering

Recently, piezocatalytic technology has been recognized as an efficient and viable strategy for the remediation of aquatic environments. Herein, a synergistic strategy of phase boundary and defect co-engineering has been proposed to enhance the piezocatalytic performance of BaTiO3-based ceramic materials: a ceramic system material ((1-x)BaTiO3-x(Ca0.9Sr0.1)(Sn0.5Hf0.5)O3, (1-x)BT-xCSSH) was constructed to achieve the coexistence of multiple ferroelectric phases by co-doping ions in the A/B-sites, and defect engineering was realized by a high-temperature annealing. The 0.95BT-0.05CSSH ceramic exhibits the coexistence of rhombic (R), orthorhombic (O), and tetragonal (T) phases, with multiple spontaneous polarization directions and low polarization rotational energy barriers, thereby demonstrating high piezoelectricity (d33 = 450 pC/N) and thus outstanding piezocatalytic performance. The degradation rate/reaction rate constant of the 0.95BT-0.05CSSH ceramic material for rhodamine B (RhB) is 71.35 %/13.5 × 10−3 min−1. After undergoing a high-temperature annealing, the catalytic activity of the 0.95BT-0.05CSSH ceramic is further improved, resulting in a degradation rate/reaction rate constant of 92.84 %/28.5 × 10−3 min−1 for rhodamine B (RhB). The catalytic activity of the 0.95BT-0.05CSSH material is enhanced by the generation of abundant oxygen vacancies during high-temperature annealing, which facilitates the separation and migration of electron-hole pairs. In this study, we propose a novel strategy to upgrade the piezocatalytic performance of BaTiO3-based piezoelectric materials, which is useful for the remediation of aquatic environments.

Understanding and tuning negative longitudinal piezoelectricity in hafnia

Most piezoelectric materials exhibit a positive longitudinal piezoelectric effect (PLPE), while a negative longitudinal piezoelectric effect (NLPE) is rarely reported or paid much attention. Here, utilizing first-principles calculations, we unveil the origin of negative longitudinal piezoelectricity in ferroelectric hafnia by introducing the concept of weighted projected bond strength around cation in the c direction (WPBc), which is proposed to quantitatively characterize the asymmetric bonding stiffness along the strain direction. When the WPBc is anti-parallel to the direction of bulk spontaneous polarization, the polarization decreases with respect to tensile strain and leads to a negative piezoelectricity. Furthermore, to confirm the influence of WPBc on the piezoelectric effect and understand how the value of WPBc influences the piezoelectric coefficient e33, we acquire both the piezoelectric coefficient of doped hafnia and the corresponding bonding environment around each cation. The finding reveals that the more negative piezoelectric coefficient can be achieved through a concurrent achievement of the more negative average WPBc and the lower standard deviation (STD) of WPBc. In addition, the Sn-doped hafnia with the lowest average WPBc and smaller STD-WPBc is identified to have the highest piezoelectric coefficient (−2.04 C/m2) compared to other dopants, showing great potential in next-generation electromechanical devices.

Clarification of the spontaneous polarization direction in crystals with wurtzite structure

The wurtzite structure is one of the most frequently found crystal structures in modern semiconductors and its inherent spontaneous polarization is a defining materials property. Despite this significance, confusion has been rampant in the literature with respect to the orientation of the spontaneous polarization inside the unit cell of the wurtzite structure, especially for the technologically very relevant III-N compounds (AlN, GaN, and InN). In particular, the spontaneous polarization has been reported to either point up or down for the same unit cell orientation, depending on the literature source—with important implications for, e.g., the carrier type and density expected at interfaces of heterostructures involving materials with the wurtzite structure. This perspective aims to resolve this ambiguity by reviewing available reports on the direction of the energetically preferred polarization direction in the presence of external electric fields as well as atomically resolved scanning transmission electron microscopy images. While we use ferroelectric wurtzite Al1−xScxN as a key example, our conclusions are generalizable to other compounds with the same crystal structure. We demonstrate that a metal-polar unit cell must be associated with an upward polarization vector—which is contrary to long-standing conventional wisdom.

Third harmonic generation in monoclinic 2D KNbO3 with high power endurance

Two-dimensional (2D) KNbO3 is prepared by topotactic transition from 2D KNbO2 at 530 °C in air, which has a single spontaneous polarization (Ps) direction along the [101¯]pc zone axis. The strong Ps anisotropy leads to a negligible second harmonic generation of 2D KNbO3 with laser vertically incident on the sample. However, a strong third harmonic generation is observed. The effective third-order susceptibility of 2D KNbO3 with the order of ∼10−19 m2 V−2 is estimated by comparing it with the χeff(3) of graphene. The robust power tolerance of 2D KNbO3 endows it great potential in the application of high-power third harmonic generation 2D devices.

High energy density in Ag0.5Na0.5(Nb1-xTax)O3 antiferroelectric ceramics

There has been significant interest in AgNbO3-based antiferroelectric ceramics, recently, due to their ability to achieve high energy storage density (Wrec). However, fabricating their commercial products faces challenges due to chemically unstable and expensive Ag2O. To reduce Ag2O contents, we fabricated (Ag0.5Na0.5)(Nb1-xTax)O3 (ANNT100x) ceramics. The results reveal that Ta-substitution plays a dual role: inducing chemical pressure to compress the unit cell along spontaneous polarization direction, enhancing antiferroelectric stability; and increasing the band gap (Eg), boosting intrinsic breakdown strength (Eb). These crucial factors contribute to the enhanced Wrec achieved in ANNT50. Notably, ANNT50 ceramics fabricated by the rolling process exhibit higher Eb (=578 kV/cm) than the conventional process, favoring the complete triggering of “double” polarization with significantly enhanced Wrec (= 6.5 J/cm3). Discharge results indicate that the ceramic displays high power density (Pavg = 78 MW/cm3) and discharge energy (Wdis = 5.86 J/cm3), which can rival currently reported Ag(Nb, Ta)O3 ceramics.

Ferroelectric tunnel junctions: promise, achievements and challenges

Abstract Ferroelectric tunnel junctions (FTJs) have been the subject of ongoing research interest due to its fast operation based on the spontaneous polarization direction of ultrathin ferroelectrics and its simple two-terminal structure. Due to the advantages of FTJs, such as non-destructive readout, fast operation speed, low energy consumption, and high-density integration, they have recently been considered a promising candidate for non-volatile next-generation memory. These characteristics are essential to meet the increasing demand for high-performance memory in modern computing systems. In this review, we explore the basic principles and structures of FTJs and clarify the elements necessary for the successful fabrication and operation of FTJs. Then, we focus on the recent progress in perovskite oxide, fluorite, 2-dimensional van der Waals, and polymer-based FTJs and discuss ferroelectric materials expected to be available for FTJs use in the future. We highlight various functional device applications, including non-volatile memories, crossbar arrays, and synapses, utilizing the advantageous properties of ferroelectrics. Lastly, we address the challenges that FTJ devices currently face and propose a direction for moving forward.

Electrophysical properties, memristive and resistive switching of charged domain walls in lithium niobate

Charged domain walls (CDWs) in ferroelectric materials raise both fundamental and practical interest due to their electrophysical properties differing from bulk ones. On a microstructure level, CDWs in ferroelectrics are 2D defects separating regions with different spontaneous polarization vector directions. Screening of electric field of the CDW's bound ionic charges by mobile carriers leads to the formation of elongated narrow channels with an elevated conductivity in initially dielectric materials. Controlling the position and inclination angle of CDW relative to the spontaneous polarization direction, one can change its conductivity over a wide range thus providing good opportunities for developing memory devices, including neuromorphic systems. This review describes the state of art in the formation and application of CDWs in single crystal uniaxial ferroelectric lithium niobate (LiNbO3, LN), as resistive and memristive switching devices. The main CDWs formation methods in single crystal and thin-film LN have been described, and modern data have been presented on the electrophysical properties and electrical conductivity control methods of CDWs. Prospects of CDWs application in resistive and memristive switching memory devices have been discussed.

Electrophysical properties, memristive and resistive switching in charged domain walls in lithium niobate

Charged domain walls (CDW) in ferroelectric materials are interesting from fundamental and applied points of view, since they have electrical properties different from bulk ones. At the microstructural level, CDW in ferroelectrics are two-dimensional defects that separate regions of the material with different directions of spontaneous polarization vectors. Compensation of the electric field of the bound ionic charge of the CDW by mobile carriers leads to the formation of extended narrow channels with increased conductivity in the original dielectric material. By controlling the position and angle of inclination of the CDW relative to the direction of spontaneous polarization, it is possible to change its conductivity in a wide range, which opens up broad prospects for creating memory devices, including for neuromorphic systems. The review presents the current state of research in the field of formation and application of CDW formed in single crystals of uniaxial ferroelectric lithium niobate (LiNbO3, LN) as resistive and memristive switching devices. The main methods for forming CDW in single crystals and thin films of LN are considered, and modern data on the electrophysical properties and methods for controlling the electrical conductivity of CDW are presented. The prospects for using CDW in memory devices with resistive and memristive switching are discussed.

Critical roles of multiphase coexistence in boosting piezo-catalytic activity of BaTiO3-based piezoelectric ceramics

Recently, piezocatalysis induced by perovskite ferroelectric ceramics has widely been favored as a possible fascinating strategy for water remediation due to its low cost, simplicity and feasibility. Herein, a strategy of three-ferroelectric-phase coexistence is proposed to boost the piezocatalytic performance of BaTiO3-based ceramics by introducing Ca(Sn0.5Zr0.5)O3 into BaTiO3. The piezocatalysts of (1-x)BaTiO3–xCa(Sn0.5Zr0.5)O3 ceramics were prepared by a high-temperature solid-phase method. The phase structure, microstructure, electrical properties and catalytic performance of ceramics were comprehensively studied. As x increases from 0 to 0.10, the ceramics undergo the phase evolution from single tetragonal phase to multiphase (coexistence of rhombic, orthorhombic, and tetragonal phases). It is found that the phase structure of the ceramics plays a critical role in enhancing the piezocatalytic activity. The pure BaTiO3 exhibits the tetragonal (T) phase with few spontaneous polarization directions and high polarization rotational energy barrier, resulting in poor catalytic performance and low piezoelectricity. With the coexistence of rhombic (R), orthorhombic (O) and tetragonal (T) phases, the ceramic with x = 0.1 exhibits the increased spontaneous polarization directions and low polarization rotational energy barrier, leading to excellent catalytic performance and high piezoelectricity. Especially, for the ceramics with x = 0.10, the degradation rates of rhodamine B (RhB), methylene blue (MB) and methyl orange (MO) under ultrasonication reach 97 %, 93 % and 73 %, respectively. In addition, the influencing factors of piezocatalytic degradation of RhB and the catalytic mechanism are investigated. This work proposes an environmentally friendly piezoelectric material for improving the water environment and a strategy for improving the catalytic activity of BaTiO3-based lead-free piezoelectric materials.

Large electrostrain at high temperature in bismuth sodium titanate-based piezoelectric ceramics

(1-x)[0.82Bi0.5Na0.5TiO3-0.18Bi0.5K0.5TiO3]-xAgNbO3 ceramics (abbreviated as BNKT-100xAN, x = 0–0.06) are fabricated by the solid state reaction method. It is discovered that silver niobate is completely dissolved into the lattice of 0.82Bi0.5Na0.5TiO3-0.18Bi0.5K0.5TiO3 ceramics based on characterization. The relaxation mechanism and characteristics of BNKT-100xAN ceramics are analyzed by dielectric temperature spectra and AC impedance spectra. The content of ordered domains and PNRs of BNKT-4AN ceramics is optimum, which enables it possess excellent electrostrain of 0.51%. The electrostrain almost remain constant after the 104 cycles test, suggesting that it also has great fatigue resistance. After polarization at high temperature, large electrostrain of 1.4% and inverse piezoelectric constants of 2004 pm/V are obtained at 150 °C in BNKT-4AN ceramics. The ultrahigh electrostrain is mainly promoted by the larger polarizability of the <111>-oriented and <001>-oriented defect dipoles, the same direction of defect dipoles and the spontaneous polarization direction of phase, the pinning effects of the defect dipoles on the PNRs and the collinear arrangement of the PNRs. This work indicates that lead-free piezoelectric ceramics is hopeful to be applied in piezoelectrics working at high temperature. Simultaneously, a new design paradigm also is provided for the preparation of piezoelectric ceramics with excellent performance.

Pinched hysteresis loop and internal bias field in Ba4(La0.2Nd0.2Sm0.2Eu0.2Y0.2)2Ti4Nb6O30 tungsten bronze ceramics

A-site high entropy Ba4(La0.2Nd0.2Sm0.2Eu0.2Y0.2)2Ti4Nb6O30 tungsten bronze ceramics were designed and prepared by a standard solid state sintering process. First-order ferroelectric transition occurs around 240 °C on heating, while around 136 °C on cooling. Pinched and asymmetric P–E hysteresis loops were observed within and below the thermal hysteresis temperature range of the ferroelectric transition. Pinched P–E hysteresis loops were attributed to the coupling between the ferroelectric transition and the commensurate/incommensurate modulation transition. The reason for the asymmetry of the hysteresis loop was the presence of an internal bias electric field. Different measuring procedures were designed to clarify the evolution of hysteresis loop asymmetry. The existence of oxygen vacancy and Eu3+/Eu2+ was identified by x-ray photoemission spectroscopy. The electric field cycling with elevated temperatures caused defect dipoles incline to align along the direction of spontaneous polarization leading to the internal bias electric field. Due to the A-site high entropy effect, dielectric strength of Ba4(La0.2Nd0.2Sm0.2Eu0.2Y0.2)2Ti4Nb6O30 ceramics is up to 300 kV/cm, which is increased by more than 50% than that with the single element in the A1-site.

Modification of BCZT piezoelectric ceramics by modulating oxygen vacancies in different sintering atmospheres

In this work, we regulated the oxygen vacancy concentration by sintering BCZT + 0.1 mol % Y + 0.1 mol % Nb [BCZT-0.1 mol % (Y + Nb)] ceramics under air, oxygen, argon, and vacuum atmospheres and examined the effect of oxygen vacancy concentration on phase composition, crystal structure, microstructure, and electrical properties. X-ray photoelectron spectrometry and X-ray diffraction Rietveld refinement showed that the air- and oxygen-sintered ceramic samples had lower oxygen vacancy concentrations, and the oxygen octahedral lattice distortion in the samples was stable when the R-O-T phases coexisted, forming a multiphase coexistence structure with more spontaneous polarization directions. The oxygen-sintering atmosphere is important in oxygen compensation, which promotes the formation of dense microstructure, thereby increasing the Curie temperature (TC). Oxygen vacancy formation energy was low in the argon and vacuum atmospheres, and some oxygen vacancies increased the mass transfer effect and grain growth. Nevertheless, excess oxygen vacancies increased the leakage current during polarization resulting in poor polarity, which prevents directional deflection of domains and degrades performance. The vacuum-sintered sample was calcined in 1000 °C air for oxygen supplementation sintering, and as the sintering time increased, the oxygen vacancy concentration decreased, the grains grew further, the density increased, and the piezoelectric properties improved. The oxygen-sintered BCZT-0.1 mol % (Y + Nb) samples had good comprehensive electrical properties (d33 = 547 pC/N, kp = 55%, εr = 5355, Pr = 10.63 µC/cm2, EC = 1.89 kV/cm, tan δ = 0.02, and TC = 102 °C).

Exceptionally Strong Self-Powered Polarization Behaviors Involving with Bulk Photovoltaics in Highly Anisotropic 2D Hybrid Perovskite Ferroelectric Crystals

Two-dimensional (2D) hybrid perovskites take an emerging position in optoelectronics. Especially, ferroelectric crystals in this family can be potentially used as polarized light detectors because photocurrent, induced by the ferroelectric bulk photovoltaic effect (BPVE), is the function of the intersection angle between the polarization directions of polarized light and the spontaneous polarization (Ps) direction of ferroelectric crystals. Herein, exceptionally strong polarization responses to polarized light are achieved in ferroelectric crystals of (isopentylammonium)2CsPb2Br7 (1), which is closely involved with the Ps-directed BPVE. Structurally, the alternate packing of organic spacers and inorganic sheets leads to its intrinsic anisotropy of optical dichroism (αc/αa ∼ 3.1), thus creating sinusoidal photocurrents with a polarization ratio of ∼1.2 at 10 V bias. It is noteworthy that the exceptional polarization responses with a large polarization ratio of ∼7.2 can be further obtained based on its BPVE at zero bias (self-powered mode). This figure-of-merit is significantly superior to that of some 2D materials, nanowires, and homologues, e.g., ReS2 (∼3.5), GeSe (∼2.16), CsPbBr3 nanowire (∼2.6), and (n-butylammonium)2(methylammonium)Pb2Br7 (∼2.0). This work sheds light on the optimization of photoelectric behaviors on the targeted optoelectronic device applications by ferroelectric BPVE.

Engineering Application of Nanomaterial and Ferroelectric Domain Polarization to the Dynamic Structure of the Surrounding Rock of Heavy-Duty Railway with Small Clear Intersection Tunnel

With the development of national railways and railways as one of the important channels for heavy-haul transportation, the construction of heavy-haul railways must be a rapid development, which makes it inevitable that the heavy-duty situation of small-distance interchange tunnels will appear. Nanomaterials refer to materials that have at least one dimension in the three-dimensional space in the nanoscale range (1 nm∼100 nm) or are composed of them as basic units. Ferroelectric domain polarization refers to the existence of electric domains in ferroelectrics, electric domains refer to small regions with the same spontaneous polarization direction, and the boundaries between electric domains and electric domains are called domain walls. It is also urgent to study the dynamic structure of the surrounding rocks of heavy-duty railways. This article aims to study the use of nanomaterial and ferroelectric domain technology to improve the overall strength, wear resistance, toughness, and other properties of steel to ensure the safety of the surrounding rock dynamic structure of the heavy-duty railway in the small clearance intersecting tunnel. Moreover, on this basis, this article proposes the method of spraying steel with nanomaterials and the use of ferroelectric domain polarization technology. The strength and wear resistance of steel can be improved under different nanomaterial content and the degree of ferroelectric domain polarization. Sustainability and toughness have been improved, respectively. After the wear resistance experiment and analysis, the experimental results of this article show that the impact resistance of the steel increased by 18.75%. When 0.012% of CeO2 is added, the impact toughness of the steel is increased to the maximum of 3.4 J, an increase of 16.31%, and a 37% increase in wear resistance. Under the premise of ensuring the demand for heavy-duty transportation, the safety performance and sustainability of transportation are greatly improved.

Rashba effects in lead-free ferroelectric semiconductor [CH3PH3]SnBr3

First-principles density functional theory computations are used to predict Rashba effects cofunctional with ferroelectricity in a recently synthesized lead-free hybrid organic-inorganic perovskite ${\mathrm{MPSnBr}}_{3}$ (MP=methylphosphonium, ${[{\mathrm{CH}}_{3}{\mathrm{PH}}_{3}]}^{+}$). The ground state of the material is polar monoclinic with calculated spontaneous polarization of $3.01\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{C}/{\mathrm{cm}}^{2}$. It exhibits near band edges' spin splitting of up to 3.3 meV and Rashba coefficient up to 0.62 eV \AA{}. The spin textures have different topology in the conduction and valence band, which originates from the difference in the spin-momentum coupling strengths. They occur in two orthogonal planes of the Brillouin zone and are coupled to the direction of spontaneous polarization. These features persist at a finite temperature of 293 K. At 333 K, that is, above monoclinic to orthorhombic phase transition, spontaneous polarization is reduced to $0.15\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{C}/{\mathrm{cm}}^{2}$, while the maximum spin splitting and Rashba coefficient reduce slightly to the values of 2.9 meV and 0.41 eV \AA{}, respectively. The spin textures remain coupled with the polarization direction. We investigate the dependence of the aforementioned properties on the choice of computational methodology to extend the first-principles predictions to include finite temperature effects. We find that the predictions are sensitive to the methodology. Our study reveals the potential of ${\mathrm{MPSnBr}}_{3}$ for low-temperature applications in spintronics and quantum computing.

Band alignments tuned by spontaneous polarization in two-dimensional MoS2/GaN van der Waals heterostructures

The band alignment of van der Waals (vdW) heterostructures is crucial for evaluating their carrier behavioral characteristics and application prospects. The shift of energy bands on the component surfaces induced by the out-of-plane spontaneous polarization effect provides an alternative method for tuning the band alignments of vdW heterostructures. Herein, we investigated the effect of the spontaneous polarization direction of the two-dimensional (2D) buckled GaN layer on the electronic properties of 2D MoS 2 /GaN heterostructures based on density functional theory (DFT). The calculation results indicated that the varying polarization direction of the GaN layer could significantly shift the band edges of the components, thereby realizing the conversion between the type-I and II band alignments without applying an external electric field. Combining the rational design of spontaneous polarization direction and the regulation of external electric fields, specific band alignment types and bandgaps can be achieved with high efficiency and low energy consumption. Furthermore, the overlap of electronic states and new optical transitions induced by interlayer coupling improved the optical absorption coefficients and absorption ranges of MoS 2 /GaN heterostructures compared with the corresponding monolayers. The results suggest that MoS 2 /GaN heterostructures with tunable band alignments are promising candidates for future optoelectronic device applications. • Tuning the band alignments of vdW heterostructures by utilizing the out-of-plane spontaneous polarization of 2D buckled GaN. • 2D MoS 2 /GaN heterostructure converts between type-I and II band alignments by varying polarization direction of GaN layer. • 2D MoS 2 /GaN heterostructure with improved optical absorption coefficient and absorption range. • Specific bandgaps is realized under the combined action of the polarization electric field and the external electric field.

Temperature dependence of electronic structure on the ferroelectric phase transition ofBaTiO3

X-ray Raman scattering spectra of ferroelectric $\mathrm{BaTi}{\mathrm{O}}_{3}$ were measured under excitation around the Ti $K$-absorption edge. Density of states of the unoccupied Ti $3d$ state was measured using Ti $2p$ core excitations. Anisotropy was observed in the ferroelectric phase with respect to spontaneous polarization direction. This anisotropy decreased with rising temperature and vanished in the paraelectric phase. Experimental results showed the ion displacement and electronic structure are closely related, and the hybridization between Ti $3d$ and O $2p$ states affects the ferroelectric phase transition.

Spontaneous polarization effects on solid high harmonic generation in ferroelectric lithium niobate crystals

High-order harmonic generation (HHG) in ferroelectric lithium niobate (LiNbO3) is investigated theoretically by solving the semi-conductor Bloch equations. Because of the spontaneous polarization, even-order harmonics are produced in the HHG spectra of the LiNbO3 crystal driven by a monochromatic multi-cycle 3300 nm laser. Our numerical calculation shows that they are originated from the suppression of one half-optical cycle HHG process in each cycle of the driving field due to the spontaneous polarization. We also illustrate that the spontaneous polarization will increase the harmonic yield and extend the maximally attainable cutoff energy at the same time. We further report that the carrier-envelope phase dependence of HHG spectra changes from a minimum period of π rad to 2π rad when the laser polarization direction is parallel/anti-parallel to the spontaneous polarization direction in LiNbO3 crystal. This is promising to be utilized as an isolated attosecond pulse gating mechanism. Moreover, the two-color relative phase dependence of HHG in LiNbO3 is also investigated and shows broken inversion-symmetry.

Self-selective ferroelectric memory realized with semimetalic graphene channel

A new concept of read-out method for ferroelectric random-access memory (FeRAM) using a graphene layer as the channel material of bottom-gated field effect transistor structure is demonstrated experimentally. The transconductance of the graphene channel is found to change its sign depending on the direction of spontaneous polarization (SP) in the underlying ferroelectric layer. This indicates that the memory state of FeRAM, specified by the SP direction of the ferroelectric layer, can be sensed unambiguously with transconductance measurements. With the proposed read-out method, it is possible to construct an array of ferroelectric memory cells in the form of a cross-point structure where the transconductance of a crossing cell can be measured selectively without any additional selector. This type of FeRAM can be a plausible solution for fabricating high speed, ultra-low power, long lifetime, and high density 3D stackable non-volatile memory.

Study on the polarization enhancement mechanism and electrical properties of high temperature bismuth layered KxNa0.5-xBi4.46Ce0·04Ti4O15+y ceramics

KxNa0.5-xBi4.46Ce0·04Ti4O15+y (x = 0, 0.04, 0.08, 0.12, 0.16, 0.20) ceramics were synthesized by solid state reaction. The microstructure and electrical properties of the solid solutions were characterized. It is found that the doping of appropriate amount of K improved the degree of lattice distortion of the material, and the characteristic parameter b/a of lattice distortion obtained the maximum value through structural refinement at x = 0.12. A defect dipole pair (KBi″−Vo••) is formed by adjusting the defects of the material. The polarizability of defects is 4.88 × 10-37F·m2. The formation of defect dipole pairs that deflect towards the direction of spontaneous polarization reduces the difficulty of polarization and improves the piezoelectric properties. Finally, the optimal piezoelectric coefficient (d33) of NBCT-xK ceramics is 23 pC/N, and the residual polarizability (2Pr) is 4.14 μC/cm2. The values of residual polarization rate (2Pr), piezoelectric coefficient (d33) and b/a show the same trend, which will gradually decrease when their value increases to a certain extent. The dielectric loss of all samples below 200 °C are lower than 0.01, and the dielectric constant is relatively flat below 400 °C. Moreover, the Curie temperature (Tc) of KxNa0.5-xBi4.46Ce0·04Ti4O15+ybased ceramics is increased to 686.0 °C, which will enable the ceramics to be used in oilfield logging, aerospace and military fields in high temperature environment.