Preparation and Piezoelectric Properties of CuO-added(Ag_(0.75)Li_(0.1)Na_(0.1)K_(0.05_)NbO_3 Lead-free Ceramics

CuO-doped（Ag0.75Li0.1Na0.1K0.05）NbO3（ALNKN-xCuO, x = 0.2mol%） lead-free piezoelectric ceramics were prepared by the solid-state reaction method in air atmosphere. The effects of CuO addition on the phase structure, microstructure, and piezoelectric properties of the ceramics were investigated. The experimental results show that the ALNKN ceramics without doping CuO possess rhombohedral phase along with K2NbrO16- type phase and metallic silver phase. For all of the CuO-doped ALNKN ceramics, a pure perovskite structure with the orthorhombic phase was obtained by enclosing the samples in a corundum tube. A homogeneous microstructure with＇the grain size of about 1 ~tm was formed for the ceramics with 0.5mo1% CuO. The grain size increases with increasing amount of CuO. The temperature dependence of dielectric properties indicates that the ferroelectric phase of the ALNKN-xCuO ceramics becomes less stable with the addition of CuO. The ceramics with x = lm01% exhibit relatively good electrical properties along with a high Curie temperature. These results will provide a helpful guidance to preparing other AN-based ceramics by solid-state reaction method in air atmosphere.

Effect of doped Mn on piezoelectric properties of (Na_(0.5)Bi_(0.5))_ (0.92)Ba_(0.08)TiO_3 lead-free ceramics

Piezoelectric ceramics (Na0.5Bi0.5) （0.92）Ba0.08TiO3 +x%MnCO3（BNBT-Mn, x=0CD*21.6, mass fraction） were synthesized by conventional solid state reaction. The results show that when the addition of MnCO3 is 0CD*2 1.4%, BNBT-Mn ceramics exhibit a single-phase perovskite structure. With the increase of content of MnCO3, piezoelectric constant and electromechanical coupling factor increase rapidly when x is lower than 0.3. Then they both decrease when x is in the range of 0.3 and 1.6. When x=0.3, piezoelectric constant and electromechanical coupling factor reach the maximum value of 160pC/N and 58.5% respectively, which can improve the temperature stability of BNBT-Mn.

Ferroelectric and piezoelectric properties of SrZrO_3-modified Bi_(0.5)Na_(0.5)TiO_3 lead-free ceramics

The lead-free SrZrO3-modified Bi0.5Na0.5TiO3(BNT-SZ100 x, with x=0-0.15) ceramics were fabricated by a conventional solid-state reaction method. The effects of SZ addition on BNT ceramics were investigated through X-ray diffraction(XRD), scanning electron microscopy(SEM), ferroelectric and electric field-induced strain characterizations. XRD analysis revealed a pure perovskite phase without any traces of secondary phases. Ferroelectric and bipolar field induced-strain curves indicated a disruption of ferroelectric order upon SZ addition into BNT ceramics. A maximum value of remnant polarization(32 μC/cm2) and piezoelectric constant(102 pC/N) was observed at 5%(mole fraction) of SZ. Maximum value of the electric field-induced strain(Smax=0.24%) corresponding to normalized strain(Smax/Emax= d*33= 340 pm/V) was obtained at BNT-SZ9.

Piezoelectric and dielectric properties of Li_x(K_(0.46)Na_(0.54))_(1-x)Nb_(0.86)Ta_(0.1)Sb_(0.04)O_3 lead-free ceramics

Lead-free piezoelectric ceramics Lix(K0.46Na0.54)1-xNb0.86Ta0.1Sb0.04O3 (with x ranging from 0 to 0.1) were synthesized by conventional solid state sintering method. The effect of cationic substitution of Li for K and Na in the A sites of perovskite lattice on the structure, phase transition behavior and electrical properties were investigated. Morphotropic phase boundaries(MPB) between orthorhombic and tetragonal phase are found in the composition range of 0.06≤x≤0.08. Analogous to Pb(Zr,Ti)O3, the dielectric and piezoelectric properties are enhanced for the composition near the morphotropic phase boundary. The Li0.06(K0.46Na0.54)0.94- Nb0.86Ta0.1Sb0.04O3 ceramics show excellent electrical properties, that is, piezoelectric constant d33=215 pC/N, planar electromechanical coupling factor kp=41%, dielectric constant ε 3T3 /ε0=1 303, and dielectric loss tan δ=2.45%. The results indicate that Lix(K0.46Na0.54)1-x Nb0.86 Ta0.1Sb0.04O3 ceramic is a promising lead-free piezoelectric material.

Achieving excellent temperature-stable dielectric properties of Bi_(0.5)Na_(0.5)TiO_(3)-based lead-free ceramics via doping AgNbO_(3)

The lead-free ceramics(1−x)(0.94Bi0.47Na0.47Ba0.06TiO3-0.06BiAlO3)-xAgNbO3(denoted as BNBTA-xAN)were synthesized via a solid-state sintering method.The effect of AgNbO3 doping amount on dielectric properties of the ceramics was studied systematically.X-ray diffraction(XRD),scanning electron microscope(SEM)and Raman spectroscope were used to detect the structure of the ceramics.Temperature-dependent dielectric spectra,frequency-dependent dielectric constant and alternating current(ac)electric conductance at various temperatures were measured.The doping of AgNbO3 greatly reduces dielectric constant around Curie temperature and thus enhances the temperature stability of the dielectric constant.The ceramic BNBTA-0.03AN exhibits excellent temperature-stable dielectric properties with temperature coefficient of capacitance(TCC)≤±15%between 55°C and 418°C with temperature window 363°C and small changes of dielectric constant and dielectric loss from 100 Hz to 1 MHz at different temperatures.The obtained ceramics are expected to be used in high-temperature capacitors due to its excellent temperature stability.

High recoverable energy storage density of Na_(0.5)Bi_(0.5)TiO_(3) lead-free ceramics modified by Bi(Mg_(0.5)Hf_(0.5))O_(3)

Enhancing the availability and reliability of dielectric ceramic energy storage devices is of great importance.In this work,(1-x)Na_(0.5)Bi_(0.5)TiO_(3)-xBi(Mg_(0.5)Hf_(0.5))O_(3)(NBT-xBMH)lead-free ceramics were created utilizing a solid-state reaction technique.All NBT-xBMH ceramics have a single perovskite structure.With increasing BMH doping,the grain size shrinks drastically,which greatly enhances the breakdown electric field(310 kV/cm at x=0.25).Additionally,the relaxation behaviors of NBT-xBMH ceramics with high BMH content are more remarkable.Among all designed components,the NBT-0.25BMH ceramic exhibits the best energy storage performance with a high Wrec of 4.63 J/cm^(3) and anηof 75.1%at 310 kV/cm.The NBT-0.25BMH ceramic has exceptional resistance to fluctuations in both frequency(5-500 Hz)and temperature(30-100°C).Charge-discharge test shows that the NBT-0.25BMH ceramic has a quick discharge rate(t0.9<110 ns).With these properties,the NBT-0.25BMH ceramic may have applications in microdevices as well as in ultra-high power electronic systems.

Excellent energy storage properties realized in novel BaTiO_(3)-based lead-free ceramics by regulating relaxation behavior

BaTiO_(3)(BT)has attracted extensive attention among advanced lead-free ferroelectric materials due to its unique dielectric and ferroelectric properties.However,the enormous remanent polarization and coercive field severely impede the improvement of its energy storage capabilities.Here,the BaTiO_(3)e-Bi(Zn_(0.5)Hf_(0.5))O_(3)(BT-BZH)ceramics with high breakdown field strength and remarkable relaxation characteristics can be obtained by introducing the composite component BZH in BT to regulate the phase structure and grain size of the ceramics.The findings demonstrate that the improvement of energy storage performance is related to the increase of relaxation behavior.A large energy storage density(Wrec~3.62 J/cm^(3))along with superior energy storage efficiency(h~88.5%)is achieved in 0.88BT-0.12BZH relaxor ceramics only at 240 kV/cm.In addition,the sample suggests superior thermal stability and frequency stability within 25e115℃and 1e500 Hz,respectively.Furthermore,the outstanding chargedischarge properties with an ultrafast discharge time(100 ns),large discharged energy density(1.2 J/cm^(3)),impressive current density(519.4 A/cm^(2))and power density(31.1 MW/cm^(3))under the electric field of 120 kV/cm are achieved in studied ceramics.The excellent energy storage performance of BT-BZH ceramics provides a promising platform for the application of lead-free energy-storage materials.

Research of Lead-free Na_(0.5)Bi_(0.5)TiO_(3)-BaTiO_(3)System Piezoelectric Ceramics

To reduce the coercive field of Na_(0.5)Bi_(0.5)TiO_(3),Ba TiO_(3)were added as dopant materials.Then the(1-x)Na_(0.5)Bi_(0.5)TiO_(3)-xBaTiO_(3)ceramic samples were produced in solid synthetic way.The optimum preparation condition and piezoelectric properties of the samples were investigated.The XRD results show that the fabric transites from rhombohedral to tetragonal gradually with the substitution of the Ba^(2+).The morphotropic phase boundaries(MPB)exists in the composition range of 0.06.

Dielectric temperature stability and energy storage performance of NBT-based lead-free ceramics for Y9P capacitors

In this work,novel(1−x)(0.75Na_(0.5)Bi_(0.5)TiO_(3))-0.25Sr(Zr_(0.2)Sn_(0.2)Hf_(0.2)Ti_(0.2)Nb_(0.2))O_(3)-xNaNbO_(3)(NBT-SZSHTN-xNN,x=0.1,0.15,0.2,0.25)ceramics were fabricated.The influence of co-doping of NN and high entropy perovskite oxide(SZSHTN)on the phase structure,microstructure and dielectric properties of NBT-based lead-free ceramics was investigated.Dense microstructure with a grain size of~5μm is observed.When x=0.25,a wide dielectric temperature stable range of−35.4-224.3℃ with a low temperature coefficient of capacitance of<10%is achieved,fulfilling the industry standard of Y9P specification.Furthermore,excellent energy storage performance with recoverable energy density of 2.4 J/cm^(3),discharge efficiency of 71%,power density of 25.495 MW/cm^(3) and discharge rate<200 ns are simultaneously obtained,which shows great potential for high temperature capacitor applications.

(K,Na)NbO_(3)-based lead-free ceramics with enhanced temperature-stable piezoelectricity and efficient red luminescence

There has been a surge of research interest in the promising lead-free potassium-sodium niobate(KNN)-based ceramics,applications of which could be significantly promoted by improving thermal stability of piezoelectricity.Besides,endowing the KNN-based ceramics with photoluminescence property by rare-earth-ion doping can make them more completive lead-free counterparts in potential applications such as novel multifunctional sensing devices.Herein,a novel KNN-based ceramic material doped with Eu was elaborately designed to simultaneously obtain enhanced temperaturestable piezoelectricity and good luminescence property.By the introduction of diffused phase transition and the modulation of unit cell distortion,a large piezoelectric strain coefficient(d^(*)_(33))with a small variation(590±59 pm/V)over a wide temperature range(from room temperature to 110℃)was realized.The optimal composition also exhibited a considerable piezoelectric coefficient(d_(33))with small fluctuation(330±33 pC/N)from 20 to 80℃.In addition to the enhanced temperature-stable piezoelectricity,the luminescence of these ceramics was slightly enhanced with the elevation of BaZrO_(3)(BZ)doping contents,which could be attributed to the increased compositional disorder and the decreased unit cell distortion of the matrix material.Moreover,an optical characteristic was more prominent at ultra-low temperatures.This work unprecedentedly provides a novel paradigm for the design of multifunctional KNN-based ceramics with enhanced temperature-stable piezoelectricity and good luminescence property,revealing the great potential of the rare-earth-element-doped KNN material for future applications in the novel multifunctional devices.

High energy storage density and power density achieved simultaneously in NaNbO_(3)-based lead-free ceramics via antiferroelectricity enhancement

High-performance lead-free dielectric ceramics with simultaneously high energy storage density and power density are in high demanded for pulse power systems.To realize excellent energy-storage characteristics,a strategy to enhance antiferroelectricity and construct a local random field simultaneously was proposed in this study.Based on the above strategy,a series of(1-x)NaNbO_(3)-xBi(Ni_(1/2)Sn_(1/2))O3[xBNS,x=0.05,0.10,0.15,0.20,and 0.22]solid solutions were designed and fabricated.An ultrahigh energy storage density(Utotal)of 7.35 J/cm^(3),and recoverable energy density(Urec)of 5.00 J/cm^(3) were achieved in the 0.10BNS ceramics.In addition,an adequate stability of energy storage properties at a range of temperatures(20e140℃),frequencies(1e100 Hz),and fatigue test durations(1e1-10^(4) cycles)were realized in 0.10BNS ceramics.0.10BNS ceramics displayed a high current density of 1005 A/cm2,an ultrahigh power density of 100.5 MW/cm^(3,)and an ultrashort discharge time of 46.5 ns?This remarkable performance not only justified our strategy but also confirmed 0.10BNS ceramics as a promising candidate for energy storage.

Effects of Cr2O3 doping on the microstructure and electrical properties of （Ba,Ca）（Zr,Ti）O3 lead-free ceramics

Lead-free ceramics （Ba0.85Ca0.15）（Zr0.1Ti0.9）O3-x wt,%Cr2O3 （BCZT-xCr） were prepared via the conventional solid-state reaction method. The microstructure and electrical properties of BCZT-xCr samples were systematically studied. XRD and Raman results showed that all samples possessed a single phased perovskite structure and were close to the morphotropic phase boundary （MPB）. With the increase of the Cr content, the rhombohedral-tetragonal phase transition temperature （TR-T） increases slightly, and the Curie temperature （Tc） shifts towards the low temperature side. XPS analysis reveals that Cr3. and Cr5＊ ions co-existed in Cr-doped BCZT ceramics, indicating the different impact on the electrical properties from Cr ions as ＂acceptor＂ or ＂donor＂. For the x = 0.1 sample, relative high piezoelectric constants d33 （-316 pC/N） as well as high Qm （-554） and low tan6 （-0.8%） were obtained. In addition, the AC conductivity was also investigated. Hopping charge was considered as the main conduction mechanism at low temperature. As the temperature increases, small polarons and oxygen vacancies conduction played important roles.

Relaxor behavior and superior ferroelectricity of Y_(2)O_(3)-doped(Ba_(0.98)Ca_(0.02))(Ti_(0.94)Sn_(0.04)Zr_(0.02))O_(3) lead-free ceramics

To upgrade the electric properties of lead-free piezoceramics,(1-x)(Ba_(0.98)Ca_(0.02)Ti_(0.94)Sn_(0.04)Zr_(0.02))O_(3)-xY_(2)O_(3)(abbreviated as(1-x)BCTSZ-xY,x=0 mol%,0.02 mol%,0.04 mol%,0.06 mol%,0.08 mol%and 0.1 mol%)ceramics were successfully synthesized by traditional solid-state sintering method.The phase structure and microstructure of ceramics were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM)and piezoresponse force microscopyeramics(PFM).The electric properties of ceramics were researched through piezoelectric,dielectric and ferroelectric test instruments.The results show that all samples have pure perovskite structure and favorable electric properties.The optimal electric properties which especially include superior ferroelectric properties are gained when Y_(2)O_(3)content is 0.06 mol%(d_(33)=419 pC/N,k_(p)=52%,T_(c)=89.5℃,ε_(r)=26900,tanδ=2.86%,P_(r)=14.41μC/cm^(2),Ec=1.8 kV/cm).Moreover,the temperature-dependent dielectricity of samples shows apparent relaxor behavior under different frequencies.The Curie-Weiss law further proves that all samples are typical relaxor ferroelectrics,and the relaxor degree of samples decreases with increase of Y_(2)O_(3)content.In conclusion,Y_(2)O_(3)plays a significant role in enhancing electric properties of BCTSZ ceramics.

Moderate Fields, Maximum Potential: Achieving High Records with Temperature‑Stable Energy Storage in Lead‑Free BNT‑Based Ceramics

The increasing awareness of environmental concerns has prompted a surge in the exploration of leadfree,high-power ceramic capacitors.Ongoing efforts to develop leadfree dielectric ceramics with exceptional energystorage performance(ESP)have predominantly relied on multicomponent composite strategies,often accomplished under ultrahigh electric fields.However,this approach poses challenges in insulation and system downsizing due to the necessary working voltage under such conditions.Despite extensive study,bulk ceramics of(Bi_(0.5)Na_(0.5))TiO_(3)(BNT),a prominent lead-free dielectric ceramic family,have seldom achieved a recoverable energy-storage(ES)density(Wrec)exceeding 7 J cm^(−3).This study introduces a novel approach to attain ceramic capacitors with high ESP under moderate electric fields by regulating permittivity based on a linear dielectric model,enhancing insulation quality,and engineering domain structures through chemical formula optimization.The incorporation of SrTiO_(3)(ST)into the BNT matrix is revealed to reduce the dielectric constant,while the addition of Bi(Mg_(2/3)Nb_(1/3))O_(3)(BMN)aids in maintaining polarization.Additionally,the study elucidates the methodology to achieve high ESP at moderate electric fields ranging from 300 to 500 kV cm^(−1).In our optimized composition,0.5(Bi_(0.5)Na_(0.4)K_(0.1))TiO_(3)–0.5(2/3ST-1/3BMN)(B-0.5SB)ceramics,we achieved a Wrec of 7.19 J cm^(−3) with an efficiency of 93.8%at 460 kV cm^(−1).Impressively,the B-0.5SB ceramics exhibit remarkable thermal stability between 30 and 140℃ under 365 kV cm^(−1),maintaining a Wrec exceeding 5 J cm^(−3).This study not only establishes the B-0.5SB ceramics as promising candidates for ES materials but also demonstrates the feasibility of optimizing ESP by modifying the dielectric constant under specific electric field conditions.Simultaneously,it provides valuable insights for the future design of ceramic capacitors with high ESP under constraints of limited electric field.

Effect of sintering temperature on the dielectric,ferroelectric and energy storage properties of SnO_(2)-doped Bi_(0.5)(Na_(0.8)K_(0.2))_(0.5)TiO_(3)lead-free ceramics

Sintered lead-free Bi_(0.5)(Na_(0.8)K_(0.2)T_(0.5)(Ti0:96Sn0:04TO_(3)ceramics(BNKTS)have been fabricated via a solid-state reaction.The effect of sintering temperature on the structural,morphological,dielectric,ferroelectric and energy storage properties of BNKTS ceramics was investigated,and it was found that the electrical properties of the synthesized ceramics increased with the increase in the sintering temperature,and the highest values were achieved at 1100℃.The ceramics sintered at the optimized temperature of 1100℃exhibited the best physical,dielectric,ferroelectric and energy storage properties,namely,high density(the relative density,ρ=5:88 g.cm^(-3),approximate to 96.7%of the theoretical value),high densification factor(DF=0:93),high dielectric constant(ε_(r)=1215),low dielectric loss(tanδ=0:051),highest dielectric constant(ε_(max)=4335),high remanent polarization(Pr=9:5μC.cm^(-2),high coercive field(E_(c)=14:3 kV/cm),high energy storage density(0.12 J/cm^(3),and high energy storage efficiency(41.7%at 46.3 kV/cm).

Effects of A-site non-stoichiometry on the structural and electrical properties of 0.96K_(0.5)Na_(0.5)NbO_3-0.04LiSbO_3 lead-free piezoelectric ceramics

Effects of A-site non-stoichiometry on the structural and electrical properties of 0.96K0.5＋xNa0.5＋xNbO3- 0.04LiSbO3 lead-free piezoelectric ceramics were examined for 0 ≤ x ≤0.02. The piezoelectric coefficients exhibited a maximum, d33 = 187 pC/N at x = 0.0075, coinciding with the maximum of the grain size and the apparent density at x = 0.0075. The apparent density and the piezoelectric coefficients decreased with increasing x at higher x which was likely due to the crystal geometrical distortion of 0.96K0.5＋xNa0.5＋xNbO3-0.04LiSbO3. In addition, super-large grains were found and this may be due to liquid phase sintering. Excess （K＋＋Na＋） attracted a sum of space charges to keep the charge neutral, resulting in charge leakage during the course of ceramic polarization, influencing the piezoelectric and ferroelectric properties. These findings are of importance for guiding the design of Ko.sNao.sNbO3-based lead-free ceramics with enhanced electrical properties.

Dielectric and piezoelectric perfomance of lead-free ceramics of boron sodium gadolinate niobate at morphotropic phase boundary

New lead-free piezoceramic nanocomposites of Boron Sodium Gadolinium Niobate(BNGN),with general formula(1-x)B_(0.5)Na_(0.5)GdO3xB_(0.5)Na_(0.5)NbO_(3),exhibiting a Morphotropic Phase Boundary(MPB),have been synthesized following hydrothermal method followed by solid state sintering.The occurrence of MPB at the composition with x=0.55,at which rhombohedral and monoclinic phases are found to coexist,has been confirmed using powder XRD.This accounts for the occurrence of large remnant polarization when the sintered ceramic pellets are subjected to electric poling at 2KV/mm.Uniform microstructure of various compositions is confirmed by SEM imaging.Dielectric and piezoelectric properties of the samples are found to be comparable to those of commercial grade PZT.At the MPB,the d_(33)coefficient is found to be 556 pC/N,which is close to that of commercial grade PZT,which makes BNGN a promising material to substitute lead containing PZT in the near future.

Influence of sintering behavior on the microstructure and electrical properties of BaTiO_(3) lead-free ceramics from hydrothermal synthesized precursor nanoparticles

BaTiO_(3) nanoparticles were synthesized by hydrothermal method using amorphous phase TiO_(2) precursor as the Ti-source.The microstructure and phase structure were determined using XRD,SEM and Raman spectroscopy analysis results.The results showed that BaTiO_(3) nanoparticles have tetragonal structure,average size of about 100 nm was obtained at Ba/Ti ratio of 1.5,synthesis temperature of 200℃ and reaction time of 12 h.The components of the BaTiO_(3) lead-free ceramic system are fabricated by conventional solid-phase reaction from the average size BaTiO_(3) particles about 100 nm obtained by hydrothermal process.The effects of sintering behavior on dielectric,ferroelectric and piezoelectric properties of BT high-density ceramic were studied.The BaTiO_(3) ceramic composition sintered at 1300℃ has a relative density of 97%,the value of the electromechanical coefficient kp=0.40,k33=0.42,the large piezoelectric coefficient d_(33)=300 pC/N,d_(31)=−125 pC/N.

Weakly coupled relaxor behavior of BaTiO_(3)-Bi(Mg_(1/2)Ti_(1/2))O_(3) lead-free ceramics

(1-x)BaTiO_(3-x)Bi(Mg_(1/2)Ti_(1/2))O_(3)(BT-BMT,0.3≤x≤0.6)ceramics were prepared by the conventional mixed oxide method.Dielectric measurements showed highly diffusive and dispersive relaxor-like characteristics for all compositions.For0.3≤x≤0.4,all these compositions possess a stable dielectric permittivity of approximately 1500 and low loss tangent(tanδ<2%)in the.temperature range 200-400℃,which may have great potential for high-temperature applications.For all samples,examination of the polarization hy steresis behavior shows an obvious linear hysteresis loops at 120℃.It was found that the energy density of about 0.7J/cm^(3)could be achieved at 120℃for x=0.4 sample,indicating a high energy density.

Robust and Tunable Ferroelectricity in Ba/Co Codoped (K_(0.5)Na_(0.5))NbO_(3) Ceramics

The 0.98(K_(0.5)Na_(0.5))NbO_(3)-0.02Ba(Nb_(0.5)Co_(0.5))O_(3-δ) ceramics with doped Ba^(2+) and Co^(2+) ions are fabricated,and the impacts of the thermal process are studied.Compared with the rapidly cooled (RC) sample,the slowly cooled (SC) sample possesses superior dielectric and ferroelectric properties,and an 11 K higher ferroelectricparaelectric phase transition temperature,which can be attributed to the structural characteristics such as the grain size and the degree of anisotropy.Heat treatment can reversibly modulate the content of the oxygen vacancies,and in turn the ferroelectric hysteresis loops of the samples.Finally,robust and tunable ferroelectric property is achieved in SC samples with good structural integrity.