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     

Effect of SmAlO3 doping on the properties of (1-x)(K0.44Na0.52Li0.04)(Nb0.91Ta0.05Sb0.04)O3 lead-free ceramics

Journal of Electroceramics - (1-x)(K0.44Na0.52Li0.04)(Nb0.91Ta0.05Sb0.04)O3-xSmAlO3 (abbreviated as KNLNTS-xSA) (x?=?0.000, 0.001, 0.004 and 0.008) lead-free ceramics were prepared by...     

Dielectric and piezoelectric properties of KCT added (Li0.02(Na0.56 K0.46)0.98(Nb0.81Ta0.15Sb0.04)O3 ceramics

In this study, [Li_0.02(Na_0.56 K_0.46)_0.98](Nb_0.81Ta_0.15Sb_0.04)O₃ + x mol% K_5.4Cu_1.3Ta₁₀O₂₉ ceramics were fabricated by conventional solid-state solution processes. Then, their dielectric and piezoelectric properties were investigated. Sinterability of all samples was enhanced because K_5.4Cu_1.3Ta₁₀O₂₉ (abbreviated as KCT) acted as sintering aids. As the result of XRD, phase structure showed orthorhombic symmetry when KCT ≤ 0.2 mol%. Whereas, the phase structure changed from orthorhombic symmetry to tetragonal symmetry when KCT?≥?0.4 mol%. The results suggest that the orthorhombic and tetragonal phases co-exist in the composition ceramics with 0.2 mol% < KCT < 0.4 mol% at room temperature. The effects of the addition of KCT on the dielectric and piezoelectric properties were investigated. As the result, excellent properties of density=4.81[g/cm³], electromechanical coupling factor (k_p)=0.48 and piezoelectric constant(d₃₃)=252[pC/N] were obtained in the composition ceramics with 0.4 mol%KCT.     

Piezoelectric properties and domain structure of the orthorhombic (K,Na,Li)(Nb,Ta,Sb)O3 single crystal

ABSTRACT

In this work, (K,Na,Li)(Nb,Ta,Sb)O₃ (KNLNTS) crystal is in the orthorhombic phase at room temperature. The orthorhombic-tetragonal phase transition temperature is 50.0°C, and the Curie temperature T_C of the tetragonal-cubic phase transition temperature is 253.8°C. The crystal is poled, the defects were “pinned” in specific position, and has positive effect in domain wall motions and better ferroelectric property (P_r is 6.49 µC/cm², E_c is 6.66 kV/cm). The domain configrations of the crystal were studied by means of a polarizing light microscopy (PLM), with poling along [100]_C direction.     

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.     

Composition-insensitive enhanced piezoelectric properties in SrZrO 3 modified (K,Na)NbO 3 -based lead-free ceramics

In this work, composition-insensitive enhanced piezoelectric properties are achieved in (1-x)(K0.48Na0.52)0.96Li0.04(Nb0.96Sb0.04)O3-xSrZrO3 (KNN-SZ) lead-     

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).     

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.     

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.     

Structure and dielectric property of Zr-doped (Na0.47Bi0.46Ba0.06K0.01)(Nb0.02Ti0.98)O3 lead-free ceramics

(Na_0.47Bi_0.46Ba_0.06K_0.01)(Nb_0.02Ti_0.98-xZr_x)O₃ lead-free ceramics (BNBKT-xZr, x?=?0, 0.01, 0.02, 0.04) were synthesized via conventional solid state reaction method. Crystallite structure of the ceramics was studied using X-ray diffraction. The rhombohedral phase and tetragonal phase coexist in the BNBKT-xZr ceramics. The doping of Zr⁴⁺ into BNBKT lattice increases the percentage of the tetragonal phase. The size and shape of grains in the ceramics were affected by the doping of Zr⁴⁺ ions. For all the unpoled ceramics, two dielectric anomalies are observed in the dielectric constant-temperature curves. The maximum values of dielectric constant and corresponding temperatures change with the variation of Zr⁴⁺ amount. The doping of Zr⁴⁺ ions causes a decrease in the ferroelectric properties.     

The sintering behavior and microwave dielectric properties of Mg4(Nb,Sb)2O9 ceramics

The sintering behavior, microstructure and microwave dielectric properties of Mg₄(Nb_2?x Sb _x )O₉ (0?≤?x?≤?2) solid solutions were investigated systematically by X-ray diffraction(XRD), scanning electron microscopy(SEM) and a network analyzer. The solid solutions of Mg₄(Nb_2?x Sb _x )O₉ was formed with x value being no more than 1.6. The dielectric constant (?) of the sintered ceramics decreased from 13.06 to 6.28 with Sb content x from 0 to 1.6. With a substitution of Sb⁵⁺ for Nb⁵⁺ (0.04?≤?x?≤?0.08), the sintering temperature of Mg₄Nb₂O₉ ceramics was decreased from 1400 to 1300 °C without degradation of the Qf values. The optimum microwave dielectric properties of ??～?12.26, Qf?～?168,450 GHz, and τ _f?～??56.4 ppm/°C were obtained in the composition of Mg₄(Nb_1.6Sb_0.4)O₉ sintered at 1300 °C.     

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.     

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.     

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.     

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 La2O3 doped (Bi0.5Na0.5)0.92(Ba0.8Sr0.2)0.08 TiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (Bi_0.5Na_0.5)_0.92(Ba_0.8Sr_0.2)_0.08 TiO₃+x mol% La₂O₃(x = 0, 0.1, 0.3, 0.5, 0.8) were synthesized by conventional solid state reaction. The crystal structure of all compositions is mono-perovskite ascertained by XRD. The grain size decreased and diffuse phase transition behavior was more evident with the increasing amount of La₂O₃. The piezoelectric constant d₃₃ and the electromechanical coupling factor k_p showed the maximum value of 165 pC/N and 0.322 at 0.3% and 0.1% La₂O₃ addition, respectively, and rapidly decreased when La₂O₃ addition over 0.5%. The loss tangent tanδ linearly increased and the mechanical quality factor Q_m linearly decreased with the increasing amount of La₂O₃.     

Enhanced physical properties of Bi 4 Ti 3 O 12 modified Bi 0.5 (Na 0.4 K 0.1 )TiO 3 lead-free piezoelectric ceramics using crystallographic orientation techniques

In this study, bismuth titanate (Bi4Ti3O12) templates were synthesized through the molten salt method in Na2CO3 and K2CO3 fluxes. The prepared Bi4Ti3O12 te     

Piezoelectric properties and dielectric behavior of Bi1/2Na1/2[Ti1−x (Sb1/2Nb1/2) x ]O3 lead-free piezoelectric ceramics

New lead-free piezoelectric ceramics of ABO₃ perovskite type, Bi_1/2Na_1/2[Ti_1−x (Sb_1/2Nb_1/2) _x ]O₃, were synthesized by conventional solid state reaction. The effect of the replacement of complex ions of (Sb_1/2Nb_1/2)⁴⁺ in the B cationic site on structural and electrical properties was investigated. The XRD analysis showed that all samples exhibited a single phase of perovskite structure. Piezoelectric and dielectric measurement revealed that the substitution of (Sb_1/2Nb_1/2)⁴⁺ ions lead to an increase in piezoelectric constant(d ₃₃), electromechanical coupling factor(k _t), relative dielectric constant(ɛ _r),and loss tangent (tanδ), while excess of (Nb_1/2Sb_1/2)⁴⁺ ions results in a decrease in d ₃₃, k _t, ɛ _r, but an increase in tanδ. Temperature dependence of dielectric constant ɛ _r measurement indicated these compounds were relaxor ferroelectric. At low frequency and high temperature, dielectric constant increased sharply attributed to the superparaelectric clusters after (Sb_1/2Nb_1/2)⁴⁺ ions substitution.     

Synthesis and piezoelectric properties of [Bi1-z(Na1-x-y-zKxLiy)]0.5BazTiO3 lead-free piezoelectric ceramics

[Bi_1-z(Na_1-x-y-zK_xLi_y)]_0.5Ba_zTiO₃ lead-free piezoelectric ceramics were fabricated by ordinary ceramic technique and the piezoelectric and ferroelectric properties of the ceramics were studied. The ceramics can be well sintered at 1,100–1,150 °C for 2 h. X-ray diffraction (XRD) analysis shows that K⁺, Li⁺ and Ba²⁺ diffuse into the Bi_0.5Na_0.5TiO₃ lattices to form a solid solution with a single-phase perovskite structure. The introduction of K⁺, Li⁺ and Ba²⁺ into Bi_0.5Na_0.5TiO₃ significantly decreases the coercive field E _c but maintains the large remanent polarization P _r of the materials. The ceramics provide piezoelectric constant d ₃₃ of 205 pC/N, electromechanical coupling factor k _p of 0.346, remanent polarization P _r of 31.7–38.5 μC/cm², and coercive field E _c of 3.18–5.16 kV/mm.     

Piezoelectric properties of Li, Sb, and Ta co-doped (K,Na)NbO3 ceramics with fine grain size sintered by SPS method

(Na_0.52?K_0.44Li_0.04)(Nb_0.86Ta_0.06Sb_0.08)O₃ (LTS-KNN) nano-powders with the size of 11–34 nm were prepared by a sol–gel method. Using the nano-powders, LTS-KNN ceramics with fine grain size of 200–400 nm and high density were fabricated by spark plasma sintering. The satisfied piezoelectricity is obtained, such as d ^* ₃₃?~?481 pm/V, d ₃₃?~?296 pC/N, K _p?~?49.7 %, ε ₃₃ ^T /ε ₀?~?920, tanδ?~?0.025 at 1 kHz and relative density is 99.4 %, respectively. It is shown that nano-powders are suitable to prepare fine-grained potassium-sodium niobate ceramics with satisfied properties.