(K0.52Na0.44Li0.04)(Nb0.86Ta0.10Sb0.04)O3-BiFeO3无铅压电陶瓷的电性能

采用固相法制备(1-x)(K0.52Na0.44Li0.04)(Nb0.86Ta0.10Sb0.04)O3-xBiFeO3[(1-x)LF4-xBF]无铅压电陶瓷,研究BF含量(0≤x≤0.010 00)对LF4陶瓷微观结构和电性能的影响.结果表明:所有样品均具有纯的四方钙钛矿结构,引入BF能明显改善LF4陶瓷的致密性...     

Ag2O掺杂对Li0.02(Na0.52K0.48)0.98Nb0.8Ta0.2O3无铅压电陶瓷电性能影响的研究

用传统的固相无压烧结法制备了Li0.02(Na0.52K0.48)0.98Nb0.8T0.2O3-xAg2O(0≤x≤0.1)无铅压电陶瓷,研究了Ag2O掺杂对陶瓷电性能的影响.研究发现,适当掺杂Ag2O能显著提高陶瓷的电性能,在1090℃的烧结温度下,当掺杂量为0.06时,陶瓷的压电性能最佳,d33、Kp、εr、Pr均达到最大(d33=229 pC/N,Kp=55.2％,εr=802,Pr=23 μC/cm2),矫顽场降到最低(Ec=12 kV/cm),应变达到2.0％.但Ag2O的添加使陶瓷的机械品质因数Qm由139.7降到了58.8,使介电损耗tanδ由1.38％增加到了2.7％.     

BaCu0.5W0.5O3掺杂改性Li0.04Na0.52K0.44Nb0.86Ta0.140Sb0.04O3无铅压电陶瓷

以传统固相法制备了(1-x)Li0.04Na0.52K0.44Nb0.86Ta0.10Sb0.04O3-xBaCu0.5O3[简称(1-x)LF4-xBCW]无铅压电陶瓷,研究了不同BCW掺杂量(x=0%,0.1%,O.2%,O.5%,1%,摩尔分数)对LF4陶瓷的显微结构和电性能的影响.结果表明:引入BCW后,材料仍为钙钛矿结构,当x≥1%时,样品由四方相向正交相转变,出现To-t,Tc则随BCW掺入量的增加向低温区移动.BCW掺杂量对LF4的电性能起到"硬性"掺杂作用,其压电常数d33,平面机电耦合系数kp,介电损耗tan δ和介电常数εr均随着BCW含量的增加而降低,而机械品质因素Qm整体提高.此外,BCW的掺入降低了陶瓷的烧结温度并提高了其密度.     

Influence of B-site compositional homogeneity on properties of (K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3-based piezoelectric ceramics

The effect of B-site compositional homogeneity on microstructure, piezoelectric properties and dielectric behaviour of lead-free piezoelectric ceramics, (K_0.44Na_0.52Li_0.04) (Nb_0.86Ta_0.10Sb_0.04)O₃, is investigated. The B-site compositional homogeneity is evaluated by using an intermediate precursor obtained by solid state reaction between adequate amounts of Nb₂O₅, Ta₂O₅ and Sb₂O₅, calcined at 1350 °C and attrition milled. The B-site precursor powder is mixed with alkaline carbonates to synthesize perovskite powders and, finally, sinter piezoceramics. X-ray diffraction and Raman spectroscopy reveal the formation of a perovskite phase, although tetragonal tungsten-bronze structure is detected as minor secondary phase. Ceramics processed by using B-site precursor show different crystalline structure as a function of sintering conditions or K/Na ratio. The B-site precursor route produces thus lower piezoelectric properties, but the control of alkali volatilization by using sintering powder bed resulted in a relevant decrease of dielectric losses that favours the d₃₃ enhancement.     

Dielectric and impedance spectroscopy analysis of lead-free (1-x)(K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O3-xBaTiO3 ceramics

(1-x)(K_0.44Na_0.52Li_0.04)(Nb_0.86Ta_0.10Sb_0.04)O₃-xBaTiO₃ (labeled as (1-x)KNLNTS- xBT, x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10) lead-free ceramics were prepared by a solid-state sintering method. As the BT content increased, the phase of ceramics changed from orthorhombic (0.00 ≤ x ≤ 0.02) to orthorhombic-tetragonal (0.02 < x < 0.06) structure, and finally turned into tetragonal (0.06 ≤ x ≤ 0.10) structure. The Curie-Weiss law and modified Curie-Weiss law were applied to analyzing dielectric properties. With the increase of BT content, the relaxation degree increased, which indicated that the ceramics shown a excellent relaxation behavior. For 0.9KNLNTS- 0.1BT ceramics, the dispersion coefficient γ reached the maximum of 1.73, which is hugely attractive for lead-free relaxor ferroelectrics. From its variation of impedance spectroscopy with temperature, it was found that the relaxation and conduction behavior were associated with the thermal activation, and the oxygen vacancies were the potential ionic carriers. Moreover, through Arrhenius fitting, the activation energy of 0.9KNLNTS- 0.1BT ceramic was 0.82(6) eV, indicating that the oxygen vacancy concentration for the ceramics was high.     

Electric aging behavior of lead-free Li0.06(K0.48Na0.52)0.94(Nb0.86Ta0.08Sb0.06)O3 piezoelectric ceramics improved by pre-calcined method

In order to improve the piezoelectric and aging properties of the lead-free Li_0.06(K_0.48Na_0.52)_0.94(Nb_0.86Ta_0.08Sb_0.06)O₃ piezoelectric ceramics, the conventional solid-state reaction method and the B-side pre-calcined method were achieved and compared in this paper. The physical and electrical properties of the lead-free Li_0.06(K_0.48Na_0.52)_0.94(Nb_0.86Ta_0.08Sb_0.06)O₃ piezoelectric ceramics material were investigated and discussed. For the B-side pre-calcined method, the ceramic material exhibited the excellent electrical and piezoelectric parameters. Finally, the electromechanical coupling factors, the resonance frequencies, and the resonance resistances of the lead-free ceramic materials were also discussed.     

Technology and electrophysical properties of the (K0.44Na0.52Li0.04)(Nb0.9–xTa0.1Sbx)O3 ceramics

Compounds based on (K_zNa_1–z)NbO₃ (KNN) are promising lead-free ferroelectric materials that reveal good electrophysical properties. In the present work, we report the results of the study influence of the doping effect of antimony on the technology, microstructure and electrophysical properties of potassium sodium niobate ceramics modified by lithium and tantalum ions (K_0.44Na_0.52Li_0.04)(Nb_0.9–xTa_0.1Sb_x)O₃ (KNLNTSbx). The four KNLNTSbx ceramic compositions were designed:

1. (K_0.44Na_0.52Li_0.04)(Nb_0.9Ta_0.1)O₃ (for x_Sb?=?0),

2. (K_0.44Na_0.52Li_0.04)(Nb_0.88Ta_0.1Sb_0.02)O₃ (for x_Sb?=?0.02),

3. (K_0.44Na_0.52Li_0.04) (Nb_0.87Ta_0.1Sb_0.03)O₃ (for x_Sb?=?0.03),

4. (K_0.44Na_0.52Li_0.04) (Nb_0.86Ta_0.1Sb_0.04)O₃ (for x_Sb?=?0.04).

All ceramic powders were synthesised by the standard solid-state reaction method from the mixture of oxides and carbonates. The paper presents the technology and results of crystal structure, microstructural, dielectric properties, as well as DC electrical conductivity of the KNLNTSbx ceramics. The conducted research proved that suitable doping of the KNN materials improves the sinterability of the ceramic compositions and positively influences the useful electrophysical properties thereof.     

Sb3+掺杂Li0.02(Na0.53K0.48)0.98Nb0.8Ta0.2O3无铅压电陶瓷的电学性能

用传统的固相反应烧结法制备了Li0.02(Na0.53K0.48)0.98 Nb0.8Ta0.2O3-xSb2O3(LNKNT-xSb2O3)无铅压电陶瓷,研究了Sb3+掺杂对陶瓷晶体结构、显微结构及压电性能的影响.研究结果表明,Sb3+掺杂LNKNT陶瓷属于明显的“软性”掺杂,少量掺杂Sb3+能显著提高陶瓷的烧结及压电性能.当烧结温度为1100℃,掺杂量为2wt％时,LNKNT-0.02Sb陶瓷达到最好的压电性能:d33=193 pC/N,KP=49.5％,εr=779,Pr=16μC/cm2,应变达到2.3％,但机械品质因数QM从110.97降低到了85,介电损耗tanδ从1.66％增加到了2.01％.     

Phase transition and electrical properties of Bi0.5(Na0.8K0.2)0.5ZrO3 modified (K0.52Na0.48)(Nb0.95Sb0.05)O3 lead-free piezoelectric ceramics

In this work, (1−x)(K_0.52Na_0.48)Nb_0.95Sb_0.05O₃−xBi_0.5(Na_0.8K_0.2)_0.5ZrO₃ [abbreviated as (1−x)KNNS−xBNKZ, x=0–0.06] lead-free ceramics were fabricated using solid-state reaction method. The effects of BNKZ contents on the phase structure, piezoelectric and ferroelectric properties were investigated. The phase boundaries including orthorhombic-tetragonal (O-T) and rhombohedral-tetragonal (R-T) multiphase coexistence were identified by XRD patterns and temperature-dependent dielectric constant by adding different content of BNKZ. A giant field induced strain (~0.25%) along with converse piezoelectric coefficient d₃₃^* (~629.4 pm/V) and enhanced ferroelectricity P_r (~38 μC/cm²) were obtained when x=0.02, while the specimen with x=0.03 presented the optimal piezoelectric coefficient d₃₃ of 215 pC/N, due to the O-T or R-T phase coexistence near room temperature respectively. These results show that the introduction of Bi_0.5(Na_0.8K_0.2)_0.5ZrO₃ is a very effective way to improve the electrical properties of (K_0.52Na_0.48)(Nb_0.95Sb_0.05)O₃ lead-free piezoelectric ceramics.     

Phase transition behavior and electrical properties of (1 − x)Bi0.5Na0.5TiO3–x(Na0.53K0.44Li0.04)(Nb0.88Sb0.08Ta0.04)O3 lead-free ceramics

(1 ? x)Bi_0.5Na_0.5TiO₃–x(Na_0.53K_0.44Li_0.04)(Nb_0.88Sb_0.08Ta_0.04)O₃ (BNT–xNKLNST) with x = 0–0.10 lead-free piezoelectric ceramics were prepared by a solid state method, and the structure and electrical properties were investigated in this study. It is found that a morphotropic phase boundary (MPB) of rhombohedral (R) and tetragonal (T) phase exists in the range of 0.03 ≤ x ≤ 0.05 and the structure changes to paraelectric phase when x > 0.07. The samples with x = 0.05 exhibit improved electrical properties owing to the formation of MPB, which are as follows: piezoelectric constant d₃₃ = 120 pC/N, remnant polarization P_r = 39.4 μC/cm² and coercive field E_c = 3.6 kV/mm. These results indicate that the enhanced piezoelectric properties for BNT can be achieved by forming the coexistence of R and T phase.     

Li2O excess (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 lead free piezoelectric ceramics

1 mol% Li₂O excess (Na_0.51K_0.47Li_0.02)(Nb_0.8Ta_0.2)O₃ ceramics were prepared by the conventional mixed oxide method and sintered from 950 to 1200 °C. Also, Li₂O was employed as a sintering aid for high densification and low temperature sintering process. X-ray diffraction results of 1 mol% Li₂O excess (Na_0.51K_0.47Li_0.02)(Nb_0.8Ta_0.2)O₃ lead free piezoelectric ceramics indicated that the specimens were well crystallized and have tetragonal structure. The specimens which sintered at 1050 °C showed the highest piezoelectric properties compared with others. The measured piezoelectric constant and electromechanical coupling coefficient were 231 pC/N and 38.9%, respectively. Curie temperature of (Na_0.51K_0.47Li_0.02)(Nb_0.8Ta_0.2)O₃ ceramics was 344.32, 344.4 and 344.5 °C at 1, 10 and 100 kHz, respectively.     

Enhanced energy storage performance in Na(1-3x)BixNb0.85Ta0.15O3 relaxor ferroelectric ceramics

High-performance lead-free dielectric containers have excellent energy storage performance such as higher power density and energy density. While being eco-friendly materials, lead-free dielectric materials are more suitable for pulse power systems than other dielectric materials. In this study, Ta⁵⁺and Bi³⁺ ions were introduced into the A site and B site of the NaNbO₃ matrix. The introduction of Bi³⁺ ions induced the formation of a vacancy in the A site, yielding Na_(1-3x)Bi_xNb_0.85Ta_0.15O₃ (NBNT, x = 0.05, 0.08, 0.11, 0.14) ceramics. The recoverable energy density (W_rec) and the energy storage efficiency (η) were highest for the Na_0.67Bi_0.11Nb_0.85Ta_0.15O₃ ceramic, with values of 3.37 J/cm³ and 89% respectively. Batteries employing the Na_0.67Bi_0.11Nb_0.85Ta_0.15O₃ ceramic achieved a current density of 830.4 A/cm², an energy density of 49.8 MW/cm³ and 60.2 ns discharge time. These results show that the Na_0.67Bi_0.11Nb_0.85Ta_0.15O₃ ceramic is an effective energy storage material with broad application prospects.     

Preparation,microstructure and electrical property of GdSmZr2O7-(Li0.52Na0.48)2CO3 composite electrolyte via carbonate infiltration

Porous GdSmZr₂O₇ (GSZ) with different porosities has been prepared by the solid state reaction, and GSZ-carbonates composites have been prepared by infiltrating (Li_0·52Na_0.48)₂CO₃ (LNC) molten carbonates. Phase structure, microstructure and electrical property have been analyzed by X-ray diffractometer (XRD), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS). SEM results show that the voids in porous GSZ are uniformly distributed. The relative density of GSZ-LNC composites obtained by molten salt infiltration is above 93%. The electrical conductivity of the GSZ-LNC composites obtained by molten salt infiltration reaches the highest value of 0.50 S cm⁻¹ at 600 °C, which is much higher than that of GSZ-LNC composites prepared by traditional mechanical mixing method. This excellent electrical property strongly indicates that the GSZ-LNC composite obtained by molten salt infiltration is a promising ionic conductor.     

Effects of excess amount of K and Na on properties of (K0.48Na0.52)NbO3 thin films

The excess amounts of K and Na in precursor solutions are very important for the phase structure and performance of (K_0.48Na_0.52)NbO₃ (KNN) thin films because of their volatilization loss. However, there are no identical opinions have been reported that could describe which element is easily volatile. In this paper, different excessive amounts of K and Na are added simultaneously in precursor solutions, the lead-free KNN thin films are prepared by metallorganic compound decomposition (MOD) method. Through comparison of phase structures, dielectric properties, J–E characteristic and ferroelectric P–E hysteresis loops, the effects of chemical componential fluctuation of K and Na on properties of KNN thin films are discussed systematically.     

Phase structure and enhanced piezoelectric properties in (1-x)(K0.48Na0.52)(Nb0.95Sb0.05)O3-x(Bi0.5Na0.42Li0.08)0.9Sr0.1ZrO3 lead-free piezoelectric ceramics

The piezoelectric properties of KNN lead-free piezoelectric ceramics could be greatly enhanced by forming multiphase coexistence. In this work, binary system (1-x)(K_0.48Na_0.52)(Nb_0.95Sb_0.05)O₃-x(Bi_0.5Na_0.42Li_0.08)_0.9Sr_0.1ZrO₃ [(abbreviated as (1-x)KNNS-xBNLSZ] ceramics with rhombohedral-tetragonal (r-T) phase boundary was designed and synthesized using the conventional solid-state sintering method, and effects of BNLSZ contents on their micrograph, phase structure and electrical properties were also investigated. According to phase diagram from the results of temperature-dependent capacitance and dielectric constant, the ceramics exhibit the R-T phase coexistence in the composition range of 3.5%≤x<4.5%, and an enhanced dielectric, ferroelectric, and piezoelectric behavior was obtained at such a phase boundary zone. As a result, the ceramics with x=0.04 exhibit optimum electrical properties of d₃₃~461 pC/N, k_p~46%, tan δ~0.03, P_r~16.9 μC/cm², and E_c ~9 kV/cm, together with a Curie temperature (T_C) of ~228 °C. Such a good comprehensive performance obtained in this present work is due to the R-T phase transition and enhanced ɛ_rP_r. It was believed that this ceramic system would promote the development of KNN-based lead-free ceramics.     

Structure,microstructure and electrical properties of Cu2+ doped (K,Na,Li)(Nb,Ta,Sb)O3 piezoelectric ceramics

This work studies the effects of copper doping on the properties of the (K_0.44Na_0.52Li_0.04)(Nb_0.86Ta_0.10Sb_0.04)O₃ piezoelectric ceramic material. Cu²⁺ incorporation into the perovskite structure produces a transformation of the crystalline lattice from tetragonal to orthorhombic symmetry together with an increase of the secondary phase. The grain size of the ceramic samples is increased due to the formation of a liquid phase during sintering, which increases with the Cu²⁺ content. EDS analysis reveals that the secondary-phase regions present a Cu and Nb-rich composition, indicating that the Cu-excess accommodates through the formation of this secondary phase. Cu-doping induces a rapid increase of the orthorhombic–tetragonal phase transition temperature, while the tetragonal–cubic phase transition temperature is decreased, the latter becoming more diffuse with the increase of Cu content. The piezoelectric properties of the material are reduced with the copper concentration, whereas the mechanical quality factor increases by a factor of nearly four.     

Structural and Physical Properties of Nd-Doped Pb(Zr0.52Ti0.48)O3 Ceramics

Lead zirconate titanate (PZT) ceramics (Zr/Ti = 52/48) have been modified with different quantities of neodymium oxide (Nd₂O₃). The preparation was carried out via the solid-state-reaction route. The samples were calcined and sintered at 850°C and 1200°C, respectively. The structural evolution and the microstructure were investigated using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM), respectively. The physical properties such as dielectric constants, piezoelectric coefficients, density etc. were also studied.     

Preparation and characterization of lead-free (K0.47Na0.51Li0.02)(Nb0.8Ta0.2)O3 piezoceramic/epoxy composites with 0–3 connectivity

Lead-free (K_0.47Na_0.51Li_0.02)(Nb_0.8Ta_0.2)O₃ (KNLNT) piezoceramic/epoxy composites with 0–3 connectivity were prepared using cold-pressing. The dielectric and piezoelectric properties of the composites were examined as a function of mean particle size (D) within the range of 27–174 μm at a fixed ceramic content of 85 vol%. The dielectric constant increased with D by the combined effects of increased connectivity and decreased surface-to-volume ratio of ceramics. When D = 125 μm, the piezoelectric constant showed a highest value of 44 pC/N that is much greater than those of previous reports on lead-free piezoelectric 0–3 ceramic/polymer composites.     

(Ba0.85Ca0.15)(Ti0.90Zr0.06Sn0.04)O3-Fe2O3无铅压电陶瓷的性能研究

采用固相法制备了(Ba0.85Ca0.15) (Ti0.90Zr0.06Sn0.04)O3-xmol％Fe2O3(简写为BCTZS-xFe)无铅压电陶瓷.研究了不同掺杂量对该陶瓷的显微结构、介电、铁电及压电性能的影响.结果表明,所有样品均具有单一的钙钛矿结构,少量掺杂能使晶粒长大,提高电性能.在x=0.025时,具有最佳的综合电性能,压电常数d33 =515 pC/N,机电耦合系数kp=48.2％,机械品质因数Qm =182,2Pr=18.2 μC/cm2,2Ec =4.3 kV/cm,介电常数εr=5175.