Piezoelectric and dielectric properties of (Na0.54K0.46)0.96Li0.04(Nb0.80Ta0.20)O3 ceramics substituted with Co

Lead-free [(Na_0.54K_0.46)_0.96Li_0.04](Nb_0.80Ta_0.20)O₃(abbreviated as NKL-NT) ceramics were synthesized by conventional solid state sintering method and the effect of Co substitution on the microstructure and piezoelectric properties were investigated. The crystal structure and microstructure were investigated by X-ray diffraction (XRD) and SEM images. The crystal structure exhibited the tetragonal structure at the composition ceramics less than 1 mol% Co. However, with increasing Co substitution from 1.5 to 2.0 mol%, the ceramics showed morphotropic phase boundary (MPB) and the crystal structure of the ceramic possessed orthorhombic structure at 3 mol% Co. The grain size was increased with increasing of Co contents. The phase transition temperature tetragonal-cubic(T_C) and orthorhombic-tetragonal(T_O-T) were shifted to downward and upward with increasing Co contents, respectively. The high piezoelectric properties of d₃₃?=?259[pC/N], k_p?=?0.43 and Qm?=?109 were obtained from the 1.5 mol% Co substituted ceramics sintered at 1060 °C for 5 h.     

Dielectric and piezoelectric properties of (K0.5Na0.5)(Nb0.97Sb0.03)O3 ceramics doped with Bi2O3

In this study, to develop the optimal composition of ceramics for low loss piezoelectric actuator and ultrasonic motor applications, (K_0.5Na_0.5)(Nb_0.97Sb_0.03)O₃?+?0.009 K_5.4Cu_1.3Ta₁₀O₂₉?+?0.1wt%Li₂CO₃?+?xwt%Bi₂O₃(x?=?0?~?0.9) lead-free piezoelectric ceramics with a fixed quantity of 0.009 K_5.4Cu_1.3Ta₁₀O₂₉ (abbreviated as KCT) were manufactured using the conventional solid-state solution processes. The effects of Bi₂O₃ addition on the dielectric and piezoelectric properties were then investigated. From the X-ray diffraction analysis result the specimens demonstrated orthorhombic symmetry when Bi₂O₃ was less 0.6?wt%, a pseudo-cubic phase appeared when Bi₂O₃ was 0.9?wt%. SEM images indicate that a small amount of Bi₂O₃ addition affect the microstructure. The piezoelectric properties of (K_0.5Na_0.5)(Nb_0.97Sb_0.03)O₃ ceramics were greatly improved by a certain amount of Bi₂O₃ addition. Excellent properties of density?=?4.54?g/cm³, relative densities?=?98.5?%, k _p?=?0.468, Q _m?=?1,715 and d ₃₃?=?183 pC/N were obtained with a composition of 0.3?wt% Bi₂O₃     

Characteristics improvement of Li0.058(K0.480Na0.535)0.966(Nb0.9Ta0.1)O3 lead-free piezoelectric ceramics by LiF additions

In this study, a series of Li_0.058(K_0.480Na_0.535)_0.966(Nb_0.90Ta_0.10)O₃ + (x)LiF (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5 wt%) lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method. The incorporation of LiF could significantly improve the sintering ability of LKNNT ceramics by reducing the optimal sintering temperature from 1090°C to 1020°C. The crystal phases and micro-structures were analyzed by means of the X-ray diffraction and scanning electronic microscopy, respectively. The impedance analyzer was used to measure the Curie temperature, phase transition point, and electro-mechanical coupling factor. And the d₃₃ meter was used to measure the piezoelectric constants.

From the results, due to the addition of 0.2 wt% LiF, uniform and condensed grains can be obtained and hence the sintering temperature can be lowered down. As the contents of LiF increased, the orthorhombic to tetragonal phase transition points T_O-T were almost no changed, but the Curie temperature T_C decreased from 425°C (x = 0) to 405°C (x = 0.5). And furthermore, the electro-mechanical coupling factor k_p and piezoelectric constant d₃₃ were all decreased with increases of LiF contents. Hence, even though the reducing of little amount of piezoelectric characteristics, the LiF addition can improve the sintering ability of the LKNNT ceramics effectively.     

Low temperature sintering of (Ba0.85Ca0.15) (Ti0.90Zr0.10)O3 lead-free piezoceramic with the additive of MnO2

Lead-free (Ba_0.85Ca_0.15) (Ti_0.90Zr_0.10)O₃ (15/10 BCZT) piezoelectric ceramics were prepared by a standard solid solution and sintered at different temperature of 1300 °C and 1500 °C at a time. The 15/10BCZT piezoceramics were prepared at 1300 °C sintering temperature by doping different amount of MnO₂.The ceramics show a phase transition from a freoelectric tetragonal phase to a rhombohedral and tetragonal ferroelctric phase and to a single rhombohedral phase with increasing MnO₂ content. The addition of MnO₂ significantly improves the sinterbility of the 15/10BCZT piezoceramics, and reducing the sintering temperature from 1500 °C to 1300 °C by 200 °C but showing comparable piezoelectric properties. With 0.4 mol% of the dopant, ～96.5% of the theoretical density of the ceramics was achieved with excellent piezoelectric coefficient d₃₃ ~ 534pC/N, which is nearly equal to the value obtained from the ceramics sintered at 1500 °C which has a piezoelectric coefficient d₃₃ ~ 570pC/N, high density (~ 5.59 g/cm³), maximum remnant polarization (P_r = 24 μC/cm²), relatively large grain size (10.4 μm) and the least coercieve field (E_c = 0.42 kV/mm). However, a high concentration of MnO₂ deterioated the properties of the ceramics because of increasing of oxygen vacancies and associated defects. The results indicate that the BCTZ-y mol% MnO₂ ceramics are one of the promising lead-free piezoelectric candidates for high temperature applications.

     

Piezoelectric properties of (Na0.465K0.465Bi0.07)(Nb0.93Ti0.07)O3 ceramics with MnO2 addition

In this study, (Na_0.465K_0.465Bi_0.07)(Nb_0.93Ti_0.07)O₃ ceramics with MnO₂ addition were prepared by conventional mixed oxide method. The effects of MnO₂ addition on the structural and electrical properties of the specimens were investigated for the application of piezoelectric devices. As the results of X-ray diffraction analysis, all specimens showed the typical polycrystalline perovskite structure without presence of the second phase. Sintered densities increased with increasing the addition amount of MnO₂ and the specimen added with 0.06 mol% of MnO₂ showed the maximum value of 4.87 g/cm³. Average grain size increased and densification increased with an increasing of MnO₂ contents. The electromechanical coupling factor, dielectric constant, dielectric loss, d₃₃ and Curie temperature of the 0.06 mol% of MnO₂ doped (Na_0.465K_0.465Bi_0.07)(Nb_0.93Ti_0.07)O₃ specimens were 0.32, 1309, 0.016, 122 and 465 °C, respectively.     

Effect of sintering temperature on piezoelectric and dielectric properties of 0.98(Na0.5K0.5)NbO3-0.02Li(Sb0.17Ta0.83)O3+0.01wt%ZnO ceramics

We studied sintering temperature to enhance the piezoelectric and dielectric properties of 0.98(Na_0.5?K_0.5)NbO₃-0.02Li(Sb_0.17Ta_0.83)O₃?+?0.01wt%ZnO (hereafter NKN-LST+ZnO) lead free piezoelectric ceramics. The synthesis and sintering method were the conventional ceramic technique and sintering was executed at 1080?～?1120°C. We found that optimal sintering temperature and NKN-LST+ZnO ceramics showed the highest piezoelectric properties and dielectric properties at the optimal sintering temperature. The NKN-LST+ZnO ceramics sintered at 1090°C show a superior performance with piezoelectric constant d ₃₃?=?185 pC/N, k _p?=?0.36, ε ₃₃ ^T /ε₀?=?491 respectively. These results reveal that NKN-LST+ZnO ceramics are promising candidate materials for lead-free piezoelectric application.     

Preparation,characterisation, and electrical properties of (K0.5Na0.5)NbO3 lead-free piezoelectric ceramics

Na_0.5?K_0.5NbO₃ (KNN) ceramics were sintered at different temperatures (970 °C, 1000 °C, 1030 °C, 1060 °C, and 1090 °C) for 3 h by a pressureless sintering method. The powders had been synthesised by sol–gel method, using citric acid as a coordination agent and ethylene glycol as an esterifying agent. The effects of temperature on the phase, microstructure, dielectric, ferroelectric, and piezoelectric properties of the as-prepared ceramics were analysed. The results revealed that all of the ceramics had a pure perovskite phase with orthorhombic symmetry. The piezoelectric constant (d ₃₃), the relative dielectric constant (ε _r), the planar electromechanical coupling coefficient (K _p), and the remnant polarization (P _r) initially increased and then decreased with increasing of temperature in such KNN ceramics. The volatilization of sodium and potassium increased with increasing sintering temperature. Over the range of temperatures studied, those ceramics sintered at 1060 °C had the following optimal properties: (ρ?=?3.97 g/cm³, d ₃₃?=?119 pC/N, ε _r?=?362.46, tan δ?=?0.05, K _p?=?0.23, P _r?=?11.97 μC/cm², E _c?=?10.35 kV/cm, and T _c?=?408 °C).     

Lead-free K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>NbO<Subscript>3</Subscript>–Bi<Subscript>0.5</Subscript>Li<Subscript>0.5</Subscript>ZrO<Subscript>3</Subscript>–BiAlO<Subscript>3</Subscript> ternary ceramics: Structure and piezoelectric properties

Lead-free perovskite (0.995–x)(K_0.5Na_0.5)NbO₃–x(Bi_0.5Li_0.5)ZrO₃–0.005BiAlO₃ ternary piezoelectric ceramics were projected and prepared by a conventional solid-state method. A research was conducted on the effects of (Bi_0.5Li_0.5)ZrO₃ content on the structure and piezoelectric properties of the ceramics. By combining the X-ray diffraction patterns with the temperature dependence of dielectric properties, a rhombohedral–orthorhombic–tetragonal phase coexistence was identified for the ceramics with 0.02 ≤ x ≤ 0.025, and a rhombohedral–tetragonal phase boundary was determined in the composition x = 0.03. Upon further increasing the (Bi_0.5Li_0.5)ZrO₃ content, the rhombohedral–tetragonal phase boundary transformed to a single rhombohedral structure with x ≥ 0.035. An obviously improved piezoelectric activity was obtained for the ceramics with compositions in and around the rhombohedral–tetragonal phase boundary, among which the composition x = 0.025 exhibited the maximum values of piezoelectric constant d ₃₃, and planar and thickness electromechanical coupling coefficients (k _p and k _t), of 252 pC/N, 0.366, and 0.466, respectively. In addition, the ceramic with x = 0.025 was found to possess a relatively high Curie temperature of 368 °C, suggesting it may have a prospect for applications at elevated ambient temperatures.     

PIEZOELECTRIC PROPERTIES OF ((Na0.5K0.5)1−xLix)(Nb0.8Ta0.2)O3 CERAMICS

ABSTRACT

In the ((Na_0.5K_0.5)_1?x)Li_x)(Nb_0.8Ta_0.2)O₃ (NKLNT) system, dense ceramics were developed by conventional sintering process. The electrical properties of NKLNT ceramics were investigated as a function of Li substitution. When the sample sintered at 1100°C for 4 h with the substitution of 2 mol% Li at the morphotropic phase boundary, electro-mechanical coupling factor (k_P) and piezoelectric coefficient (d₃₃) were found to reach the highest values of 0.42 and 210 pC/N, respectively. These excellent piezoelectric and electromechanical properties indicate that this system is potentially good candidate for lead-free material for a wide range of electro-mechanical transducer applications.     

Piezoelectric and ferroelectric properties of textured (Na0.50K0.47Li0.03)(Nb0.8Ta0.2)O3 ceramics by using template grain growth method

(Na_0.50K_0.47Li_0.03)(Nb_0.8Ta_0.2)O₃ ceramics were fabricated by tape casting technique and template grain growth method with sintering additives. The Li and Mn 1 mol% sintering additives are highly efficient for textured grain growth method in (Na_0.50K_0.47Li_0.03)(Nb_0.8Ta_0.2)O₃ ceramics. Grains are well-oriented and piezoelectric coefficient d ₃₃ is 310 pC/N. Piezoelectric coefficients d ₃₃ are proportional to the grain orientations in ceramics prepared by various methods. Ferroelectric phase transition temperature is increased in oriented ceramics. Ferroelectric polarization is decreased but coercive field is increased in the oriented ceramics.     

Phase transition,microstructure and properties of (Na<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>)<Subscript>1-x</Subscript>Ba<Subscript>x</Subscript>TiO<Subscript>3</Subscript> lead-free piezoelectric ceramics

In this article, (Na_0.5Bi_0.5)_1-xBa_xTiO₃ lead-free piezoelectric ceramics were prepared by solid-state reaction. The influence of Ba contents on phase structures, compositional distribution and electrical properties of (Na_0.5Bi_0.5)_1-xBa_xTiO₃ ceramics were systematically investigated to further understand the nature of phase transition. It was found that the phase structure of (Na_0.5Bi_0.5)_1-xBa_xTiO₃ transforms from rhombohedral to tetragonal symmetry at x = 0.06 ~ 0.07 and Ba²⁺ segregation forms the coexistence of Ba-rich tetragonal and Ba-deficient rhombohedral phases close to MPB. The electrical properties of prepared samples regularly changed with Ba content, which is closely related to the distribution of rhombohedral and tetragonal phases. The prepared sample near MPB exhibited the largest dielectric constant and the excellent piezoelectric properties (the maximal measuring field reached 78 kV/cm and the piezoelectric constant d ₃₃ = 151pC/N).     

Sintering and dielectric properties of (Ta2O5)1−x (TiO2) x polycrystalline ceramics

(Ta₂O₅)_1?x (TiO₂) _x system ceramics has been studied intensively as a promising dielectric material for next generation of high density dynamic random access memories instead of SiO₂ and Si₃N₄. It is found that the dielectric permittivity of (Ta₂O₅)_1?x (TiO₂) _x ceramics was dependent of fabrication process. But in the previous work, their calcining and sintering time were too long, generally for 24 h or even more. A relatively quick sintering process was provided which calcining and sintering time can be decreased to 12 h at 1200°C and 1 h at 1550°C, respectively. This kind of sintering process can save a lot of energy and time that is in favor of the industrial production. Under this sintering process, the composition dependent dielectric properties of (Ta₂O₅)_1?x (TiO₂) _x ceramics have been studied in a wide range of composition (0.01?≤?x?≤?0.20), and the dielectric constants of most compositions can be drastically enhanced. The maximum dielectric value can reach 216 at composition x?=?0.04. In the meantime, the mechanism of improvement of ceramic dielectric constants sintered at 1550°C was also discussed.     

Phase Formation,Dielectric, Ferroelectric and Magnetic Properties of Cr2O3 Doped (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 Ceramics

Abstract

In this paper, we studied the effect of Cr₂O₃ doping (0–0.8?wt%) on the phase formation, dielectric, ferroelectric and magnetic properties of (Ba_0.85Ca_0.15)(Ti_0.90Zr_0.10)O₃ (BCTZ) ceramics prepared by the solid state combustion method. All samples were prepared with a calcined and sintered temperature of 1050?°C and 1450?°C, respectively, for 2?h. The results of the XRD patterns showed the coexistence between the tetragonal (T) and orthorhombic (O) phases for all samples, and the tetragonal phase increased with increasing amounts of Cr₂O₃. The dielectric constant decreased when Cr₂O₃ increased. The P-E hysteresis loops of the BCTZ ceramics doped with Cr₂O₃ between 0 and 0.2?wt% showed slim and saturated loops. By increasing Cr₂O₃ doping from 0.4 to 0.8?wt%, the P-E loops were unsaturated and a leakage current was produced. The undoped BCTZ ceramics exhibited diamagnetic behavior. The sample with 0.2?wt% Cr₂O₃ showed ferromagnetic behavior. Increasing Cr₂O₃ doping from 0.4 to 0.8?wt%, caused the ceramics to exhibit paramagnetic behavior. Doping with Cr₂O₃ led to improper ratios between the tetragonal and orthorhombic phases, decreased density and increased porosity which caused a decrease in the electric properties.     

Low-temperature sintering of Li2O-doped BaTiO3 lead-free piezoelectric ceramics

Low-temperature sintering of BaTiO₃ ceramics using Li₂O as sintering aids was investigated with a special influences of Li₂O content (0–4?mol%) and sintering temperature (1000–1100°C) on crystalline structure and electrical properties. The sinterability of BaTiO₃ ceramics significantly improved by adding Li₂O, whose densification sintering temperature reduced from 1300°C to 1000°C. XRD pattern indicated that BaTiO₃-xLi₂O samples were single phase with a tetragonal symmetry as x?=?0–0.3?mol%, while the samples became an orthorhombic symmetry as x?=?0.5–4?mol%. The densification sintering temperature in which samples showed relative density higher than 90?% decreased with increasing Li₂O content. A maximum d ₃₃ value (200 pC/N) was obtained for the BaTiO₃-0.5?mol%Li₂O sample sintered at 1050°C, which is attributed to a vicinity of the phase transition and the high density. Adding Li₂O not only reduced the sintering temperature but also obtained the acceptable piezoelectric properties, which will make BaTiO₃ become a kind of promising and practical lead-free piezoelectric ceramics.     

Piezoelectric characteristics of low temperature sintering Pb(Ni1/3Nb2/3)O3–Pb(Zr1/2Ti1/2)O3 ceramics as a function of Pb(Mn1/3Sb2/3)O3 substitution

In this study, in order to develop the composition ceramics for multilayer ceramic for ultrasonic nozzle and ultrasonic actuator application, Pb(Mn_1/3Sb_2/3)O₃ (abbreviated as PMS) substituted Pb(Ni_1/3Nb_2/3)O₃–Pb(Zr,Ti)O₃ (abbreviated as PNN-PZT) ceramics were fabricated using two-stage calcinations method and Li₂CO₃, Na₂CO₃ and ZnO as sintering aids, and their piezoelectric and dielectric characteristics were investigated. With the increase of the amount of PMS substitution, electromechanical coupling factor (k _p), and mechanical quality factor (Q _m) of specimens showed the maximum value at 3 mol% substituted specimen while dielectric constant (? _r) was decreased. At the sintering temperature of 900 °C, the density, ? _r, k _p, and Q _m of 3 mol% PMS substituted PNN-PZT composition ceramics showed the optimal values of 7.92 [g/cm³], 959, 0.584, and 1003, respectively, for low loss multilayer piezoelectric actuator application.     

Nonstoichiometric (K,Na)NbO3 ceramics: Densification and electrical properties

In order to clarify the influence of excess ions in A or B sites on perovskite (K,Na)NbO₃ ceramics, various compositions of (K_0.48Na_0.52)Nb_1+x%O₃ (ABO₃) ceramics where x is in the range of ±1 % were prepared by conventional solid state method and their densification, structure, dielectric and piezoelectric properties were investigated. Results showed that a small amount of excess A-site ions could compensate for the deficiency of K and Na ions in A-sites caused by volatilization resulting in good piezoelectric properties. The ceramics with x?=??0.1 exhibited optimum piezoelectric properties with d ₃₃?=?127pC/N and k _p?=?0.41. However, presence of too much alkali elements (x?<??0.5) led to deterioration of density, dielectric and piezoelectric properties, although the crystal structure was not changed. The electrical properties, on the other hand, were not sensitive to the B-site excess ions. These results are expected to be very useful for further designing of (K,Na)NbO₃-based ceramics as lead-free alternatives to piezoelectric materials.     

Dielectric and piezoelectric properties of (0.90-x) PIN-xPT-0.10PZ ternary system near morphotropic phase boundary

The (0.90-x)Pb(In_1/2Nb_1/2)O₃-xPbTiO₃-0.10PbZrO₃ (PINTZ10) ceramics are prepared by solid state reaction and their structural, dielectric and piezoelectric properties near morphotrophic phase boundary (MPB) has been examined systematically. The structure undergoes a gradual change from rhombohedral to tetragonal when the PbTiO3 content (x) is increased. From the frequency and temperature dependent dielectric measurement it is found that the dielectric relaxation (ΔT) decreases with Ti⁴⁺ substitution. Even though the MPB of this ternary system is formed with lower PT content (0.62PIN-0.28PT-0.10PZ), the substitution of Zr⁴⁺ in the B site maintains the transition temperature (T_m) at 300 °C resembling its binary, 0.67PIN-0.37PT. The higher saturation polarization obtained for x?=?0.27 and the high piezoelectric co-efficient obtained for x?=?0.29 substantiate the existence of MPB between these two compositions.     

Pyroelectric, dielectric, and piezoelectric properties of MnO2-doped (Na0.82 K0.18)0.5Bi0.5TiO3 lead-free ceramics

MnO₂ doped (Na_0.82 K_0.18)_0.5Bi_0.5TiO₃ lead-free piezoelectric ceramics were prepared by conventional solid-state reaction process and the effect of MnO₂ addition on the pyroelectric, piezoelectric and dielectric properties were studied. The experiment results showed that the pyroelectric, piezoelectric, and dielectric properties strongly depended on MnO₂ addition in the (Na_0.82 K_0.18)_0.5Bi_0.5TiO₃ ceramics. Excellent electrical properties were obtained in (Na_0.82 K_0.18)_0.5Bi_0.5TiO₃ with 0.8?mol% MnO₂. The large dielectric loss of pure BNT ceramics was significantly reduced, the piezoelectric constant was improved, and it also showed excellent pyroelectric properties when compared with other lead free ceramics, with pyroelectric coefficient p?=?17?×?10^?4?C/m²K and figure of merit F _d ?=?6.56?×?10^?5?Pa^?0.5. With these outstanding pyroelectric properties, the 0.8?mol% MnO₂ doped (Na_0.82 K_0.18)_0.5Bi_0.5TiO₃ ceramic can be a promising material for pyroelectric sensor applications in future.     

Low temperature sintering of high performance KNN-based lead-free piezoelectric ceramic using BCBM frit as sintering aid

High performance lead-free (K_0.49Na_0.51)_0.98Li_0.02(Nb_0.77Ta_0.18Sb_0.05)O₃?+?0.5 mol%BaZrO₃ piezoelectric ceramic was selected as base material, while BaO-CuO-B₂O₃-MnO₂ frit was used as sintering aid to lower the sintering temperature. The effect of BaO-CuO-B₂O₃-MnO₂ frit doping amount on the sintering behavior, structure and electrical properties of the ceramics was investigated. The optimal sintering temperature of the ceramics decreased with the increase of frit doping amount. The ceramic with frit doping amount of 1.0 wt.%, sintered at a reduced temperature of 1100°C, exhibited optimal electrical properties as follows: piezoelectric constant d ₃₃?=?345 pC/N, planar electromechanical coupling coefficient k _p?=?44.5 %, mechanical quality factor Q _m?=?135, dielectric constant ε ₃₃ ^T ?=?1210, and dielectric loss tanδ?=?0.018. Together with its relatively high T _c?=?195°C, this ceramic was an excellent candidate for replacing the lead-based piezoceramics in practical applications.     

Enhanced piezoelectricity around the tetragonal/orthorhombic morphotropic phase boundary in (Na,K)NbO3–ATiO3 solid solutions

The high density perovskite titanates-modified potassium–sodium niobate solid solutions (1?x)(Na_0.5K_0.5)NbO₃?xBaTiO₃ and (1?x)(Na_0.5K_0.5)NbO₃?xSrTiO₃ have been prepared by the solid state reaction method. The phase diagram summarized from the dielectric property measurement reveals that there exists a tetragonal/orthorhombic morphotropic phase boundary for both the solid solutions. The piezoelectric properties show enhanced behavior at around the tetragonal/orthorhombic morphotropic phase boundary. It is believed that the origin for the high piezoelectric performance (Na,K)NbO₃-based lead-free piezoelectric ceramics is the same as that for the lead zinc niobate-lead titanate solid solution.