Conventional Mixed Oxide Method Research Articles

Effect of BaTiO3 additive on the electrical properties of Na0.50Bi0.50TiO3 lead free ceramics

The near morphotropic phase boundary (MPB) compositions of lead-free piezoelectric ceramics based on sodium bismuth titanate (Na0.50Bi0.50TiO3: NBT) and barium titanate (BaTiO3: BT) were carefully investigated by conventional high temperature mixed-oxide method. All the ceramics exhibit single phase rhombohedral symmetry. The frequency (100 Hz to 1 MHz) and temperature (Room temperature–500 °C) dependence of impedance spectroscopy of (1 − x)Na0.50Bi0.50TiO3–xBaTiO3 (x = 0.0, 0.06, 0.07 and 0.08) ceramics were investigated by impedance analyzer. The frequency explicit plots of Z″ versus frequency at various temperatures show peaks in the higher temperature range (>400 °C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The activation energy values obtained for different BT content suggest that the electrical conduction in NBT is mainly due to the mobility of the ionized oxygen defects.

Microstructure, temperature stability and electrical properties of ZnO-modified Pb(Ni1/3Nb2/3)O3–Pb(Fe1/2Nb1/2)O3–Pb(Zr0.3Ti0.7)O3 piezoelectric ceramics

Quaternary piezoelectric ceramics Pb(Ni1/3Nb2/3)O3–Pb(Fe1/2Nb1/2)O3–Pb(Zr0.3Ti0.7)O3–xZnO (PNN–PFN–PZT–xZ, x=0.0–0.08 in molar ratio) were prepared by the conventional mixed-oxide method. The effects of ZnO content on the microstructure and piezoelectric properties were systematically investigated. Increasing ZnO additive promotes the phase structure transformation from rhombohedral to tetragonal, indicating the presence of the morphotropic phase boundary in the ZnO-modified PNN–PFN–PZT system. The results show that ZnO doping significantly improves the coercive field (Ec), Curie temperature (Tc), and temperature stability (Δfr/fr 30 °C, Δd31/d31 30 °C) of the PNN–PFN–PZT–xZ ceramics, although the piezoelectric constant (d33, d31) decreases slightly with increasing ZnO content. Taking into consideration the piezoelectric property and temperature stability, the obtained ceramic sample with x=0.04 exhibited favorable properties, which are listed as follows: d33=810 pC/N, kp=0.647, εr=6243, tan δ=2.74%, Ec=4.7 kV/cm, and Tc=136 °C.

에너지수확소자용 친환경 (Li0.04(Na0.56K0.44)0.96(Nb0.9Ta0.10)0.998Zn0.005O3세라믹스의 유전 및 압전 특성

In this paper, the <TEX>$0.995(Li_{0.04}(Na_{0.56}K_{0.44})_{0.96}(Nb_{0.90}Ta_{0.10})_{0.998}Zn_{0.005}O_3+0.005KNbO_3+xwt%\;TeO_2$</TEX> lead-free piezoelectric ceramics for energy harvesting devices were fabricated by the conventional mixed oxide method. The microstructure, dielectric, and piezoelectric properties were investigated as a function of the <TEX>$TeO_2$</TEX> addition. All the specimens showed an orthorhombic phase structure. At the composition ceramics doped with 0.1 wt%<TEX>$TeO_2$</TEX>, the optimum values of <TEX>$d_{33}$</TEX>= 212 pC/N, <TEX>$d_{33}{\cdot}g_{33}=9.54pm^2/N$</TEX>, and kp=0.448 were obtained, respectively. The results indicate that the composition ceramics is a promising candidate for energy harvesting devices applications.

Effect of PMN content on the phase structure and electrical properties of PMN–PZT ceramics

Abstract x Pb(Mg 1/3 Nb 2/3 )O 3 –(1− x )Pb(Zr 0.47 Ti 0.53 )O 3 ( x PMN–(1− x )PZT) (0.15≤ x ≤0.30) ceramics were prepared by the conventional oxide-mixed method. The phase structure, ferroelectric and piezoelectric properties and field-induced strain behavior were systematically investigated. It was found that 0.25PMN−0.75PZT possessed superior electrical properties due to its composition close to the MPB (Morphotropic Phase Boundary). The composition near the MPB enables the existence of multiple polarization directions and consequently facilitates the domain reorientation, which should be responsible for the superior electrical properties. A large remnant polarization ( P r ) of 34.2 µC/cm 2 and a high piezoelectric coefficient ( d 33 ) of 698 pC/N were obtained. Especially, a large field-induced strain of 2.2‰ (at 40 kV/cm) was attained, which shows a great promise for actuator applications.

Effect of sintering temperature on microstructure and piezoelectric properties of Pb-free BiFeO3–BaTiO3 ceramics in the composition range of large BiFeO3 concentrations

Lead-free (1-x)BiFeO3–xBaTiO3 [(1-x)BF-xBT] piezoelectric ceramics in the range of large BF concentrations were prepared by conventional oxide-mixed method at various sintering temperatures. The sintering temperatures have a significant effect on the microstructure of the ceramics, and the composition has a remarkable effect on optimal sintering temperature of the ceramics, which are closely related with piezoelectric properties. The grain size increased with increasing sintering temperature and the optimal sintering temperature increased with increasing BT content. The ceramics with x = 0.275 sintered at 990 °C exhibit enhanced electrical properties of d 33 = 136pC/N and k p = 0.312 due to the polarization rotation mechanisms at MPB and desired microstructure. These results show that the ceramic with x = 0.275 is a promising lead-free high-temperature piezoelectric material.

Molten salt synthesis of YAlO3 powders

In this work, the molten salt synthesis technique was applied to the synthesis of YAlO3 powder using LiCl, NaCl or KCl salt as the flux. YAlO3 powder was synthesized by reacting equimolar amounts of Y2O3 and Al2O3 powders in LiCl salt. The synthesis temperature for YAlO3 using LiCl salt was 1300 °C which is by about 500 °C lower than that in the conventional mixed-oxide method. The synthesized powders have been characterized using powder X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FE-SEM). The effect of the salt type on the formation of YAlO3 has also been investigated.

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

In this study, (Na0.465K0.465Bi0.07)(Nb0.93Ti0.07)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 (Na0.465K0.465Bi0.07)(Nb0.93Ti0.07)O3 specimens were 0.32, 1309, 0.016, 122 and 465 °C, respectively.

Effect of sintering temperatures on the piezoelectric and dielectric properties of 0.98(Na0.5K0.5)NbO3-0.02(Ba0.5Ca0.5)TiO3 ceramics

Lead-free 0.98(Na0.5K0.5)NbO3-0.02(Ba0.5Ca0.5)TiO3 (0.98NKN-0.02BCT) ceramics were produced by using a conventional mixed oxide method with sintering temperature from 1080°C to 1120°C and their piezoelectric properties were investigated. The results indicate that the sintering temperature influences the electrical and the piezoelectric properties of 0.98NKN-0.02BCT ceramics. For the 0.98NKN-0.02BCT ceramics sintered from 1080°C to 1120°C, the piezoelectric constant d 33, electromechanical coupling factor k p , remnant polarization values P r and curie temperature T c increased with increase sintering temperature. However, for 0.98NKN-0.02BCT sintered above 1100°C, their values decreased. Piezoelectric properties of d 33 = 210 ρC/N and k p =46%, ferroelectric properties of P r = 16.2 µC/cm2 and dielectric constant ɛ r = 5159 were obtained for specimen sintered at 1100°C for 4 h. Therefore, the 0.98NKN-0.02BCT ceramics are excellent candidate materials for lead-free piezoelectric ceramics.

Non-Ohmic and dielectric properties of CaCu3Ti4O12-MgO nanocomposites

Graphical abstractDisplay Omitted Highlights? Addition of 5vol.% MgO can improve dielectric and nonlinear properties of CCTO. ? The low-frequency tan? of CCTO-MgO (5vol.%) was greatly reduced. ? e' of CCTO-MgO (5vol.%) is higher than 104 in the frequency range of 102-105Hz. ? Addition of 5vol.% MgO can enhance breakdown voltage and nonlinear coefficient. In this work, CaCu3Ti4O12-xMgO (x=0, 5, and 10vol.%) nanocomposites were prepared by a conventional mixed oxide method using CaCu3Ti4O12 and MgO nanopowders with particles sizes of about 100-300nm and 36-50nm, respectively. The dielectric and electrical properties of CaCu3Ti4O12 and CaCu3Ti4O12/MgO ceramics were investigated. The results revealed that addition of 5vol.% MgO can improve both dielectric and electrical nonlinear properties. The low-frequency loss tangent was greatly reduced; while, the dielectric constant was found to be higher than 104 in the frequency range of 102-105Hz. The decrease in a low-frequency loss tangent is caused by a decrease in DC conductivity. Addition of 5vol.% MgO can also enhance significantly the breakdown voltage and nonlinear coefficient of CaCu3Ti4O12 ceramic. Using impedance spectroscopy analysis, the increase in the breakdown voltage is attributed to an increase in the resistance of grain boundaries.

하소온도 변화에 따른 0.95(Na0.5K0.5)0.04[(Nb0.8Ta0.20)0.994Co0.015]O3-0.05KNbO3세라믹스의 유전 및 압전 특성

In this paper, the <TEX>$0.95(Na_{0.5}K_{0.5})_{0.04}[(Nb_{0.8}Ta_{0.20})_{0.994}Co_{0.015}]O_3$</TEX>(abbreviated as NKNT) + <TEX>$0.05KNbO_3$</TEX> lead-free piezoelectric ceramics were synthesized by the conventional mixed oxide method route with normal sintering. And also, the effects of calcination temperature on the microstructure, dielectric properties, and piezoelectric properties were investigated. A polymorphic phase transition(PPT) between orthorhombic and tetragonal phases was observed in specimens calcined at <TEX>$810^{\circ}C{\sim}850^{\circ}C$</TEX>. The ceramics calcined at <TEX>$830^{\circ}C$</TEX> showed excellent piezoelectric properties: <TEX>$d_{33}$</TEX>= 179 pC/N, <TEX>$k_p$</TEX>= 0.384, <TEX>$Q_m$</TEX>= 79.73). These results indicate that the ceramic is a promising candidate material for lead-free piezoelectric ceramics.

Synthesis, phase structure and dielectric property of the ZnO–MgO–SnO2 ceramics

A new dielectric ceramics with the composition of (1−x)ZnO–xMgO–SnO2 (x=0.2, 0.4, and 0.6) were prepared by conventional mixed-oxide method combined with a chemical processing. The effect of Mg content on phase structure and dielectric properties were investigated. The results show that Mg is incorporated into the solid solution (Zn,Mg)SnO3 to (Zn,Mg)2SnO4, and the substituting Mg2+ for Zn2+ improves the stability of (Zn,Mg)SnO3 ilmenite and the phase transition from (Zn,Mg)SnO3 to (Zn,Mg)2SnO4 and rutile SnO2 was weaken. The 0.2MgO–0.8ZnO–SnO2 ceramics with dense and homogeneous morphology exhibits good dielectric properties: εr=43.5, tanδ=2.69×10−4. Due to their excellent dielectric properties, (1−x)ZnO–xMgO–SnO2 ceramics can serve as the promising high-frequency dielectric capacitor.

The Effect of Firing Temperatures on (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 Ceramics Prepared via the Combustion Technique

The (Pb0.75Ba0.25)(Zr0.70Ti0.30)O3 (PBZT) ceramics were prepared via the combustion technique. (CO(NH2)2) was used as a fuel. The effect of firing temperature on PBZT's phase formation, microstructure and electrical properties were investigated. The calcination and sintering temperatures were 600°C–1000°C and 1100°C–1300°C. The pure rhombohedral perovskite was obtained from the powders calcined at 850°C. The average particle size tended to increase with increased calcination temperatures. A pure rhombohedral perovskite phase was found in all pellet samples. The average grain size and linear shrinkage tended to increase from 0.57 to 2.15 μm and from 6.8 to 15.8% with increased sintering temperatures. The dielectric results indicated the relaxer behavior of PBZT ceramics. The Curie temperature tended to decrease with increasing sintering temperatures. The highest density (∼7.39 g/cm3) and highest dielectric constant (∼8620) were obtained by using the combustion technique which was higher than the conventional mixed oxide method.

Weakly coupled relaxor behavior of BaTiO3-Bi(Mg1/2Ti1/2)O3 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. For 0.3 ≤ x ≤ 0.4, all these compositions possess a stable dielectric permittivity of approximately 1500 and low loss tangent (tan δ &lt; 2%) in the temperature range 200–400°C, which may have great potential for high-temperature applications. For all samples, examination of the polarization hysteresis behavior shows an obvious linear hysteresis loops at 120°C. It was found that the energy density of about 0.7 J/cm3 could be achieved at 120°C for x = 0.4 sample, indicating a high energy density.

Effect of Al2O3 Nanoparticles on Grain Sizes and Dielectric Properties of BaFe1/2Nb1/2O3 Ceramics

In this research, the effect of Al2O3 nanoparticles on grain size and dielectric properties of BaFe1/2Nb1/2O3 (BFN) ceramics were investigated. The powder was prepared by the conventional mixed oxide method and calcined at 900–1200°C for 4h. The optimum temperature for calcinations the pure phase, was found to be about 1100°C. The calcined powders and Al2O3 nanoparticles (0.5, 1 and 2 vol%) were ball milled with 1 wt% PVA in ethyl alcohol for 12 h using the same method as mentioned earlier. The slurry was dried, sieved and pressed into a disc shape and sintered at 1350°C for 4h with heating rate of 5°C/min. The microstructure was examined by scanning electron microscope (SEM). The dielectric constant and dielectric loss of BFN ceramics with 0, 0.5, 1 and 2 vol% Al2O3 nanoparticles were measured at 1 kHz frequency at room temperature using LCR meter. The results show that, the average grain sizes of BFN ceramics were found to decrease with the addition of the Al2O3 nanoparticles. The dielectric loss of BFN ceramics with Al2O3 nanoparticles was decreased about 40–50% of pure BFN ceramics.

Electrical and Physical Properties of Modified Potassium Sodium Niobate Ceramics Prepared by Molten Salt Synthesis

In the present work, molten salt method was applied to synthesize the 0.9875(K0.5Na0.5)NbO3–0.0125BiScO3(KNN-BS) powders. Pure phase of KNN-BS powder was obtained for a calcination temperature of 700°C which lower than a conventional mixed oxide method by 250°C. The KNN-BS ceramics were fabricated by a solid-state reaction technique. Effects of excess Na and K on the properties of the ceramics were investigated. The excess Na and K produced an increase in dielectric constant at the ferroelectric to paraelectric transition temperature as well as change the transition temperatures. Further, the ferroelectric behavior was also improved by the additives.

Dielectric Properties of (Ka0.5Na0.5)0.93Li0.07NbO3 Ceramics Under Compressive Stress

In this work, the solid solution of (Ka0.5Na0.5)0.93Li0.07NbO3 ceramics was prepared by a conventional mixed-oxide method. The structural phase formation was characterized by x-ray diffraction technique. The ceramics were identified by XRD as a single-phase perovskite structure with tetragonal symmetry. The dielectric properties under the uniaxial compressive stress of the (Ka0.5Na0.5)0.93Li0.07NbO3 ceramics were observed at stress up to 180 MPa. The results showed that the dielectric constant and the dielectric loss tangent increased with increasing the applied stress. The change of dielectric properties under the compressive stress also depended on the electrical frequency. The observations were interpreted in terms of a superposition of the intrinsic and extrinsic contributions to the dielectric properties change upon applied stress.

Effects of calcination temperature on the piezoelectric properties of lead-free Ag doped (Na,K)NbO3–LiTaO3 piezoelectric ceramics

The effects of calcinations temperature on the piezoelectric properties were investigated by employing the lead free piezoelectric Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 ceramics. Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 ceramics were prepared by employing the conventional mixed oxide method. The crystal structures and microstructure of Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 lead-free piezoelectric ceramics were examined by varying the calcination temperature from 750 to 950°C by X-ray diffraction analysis and scanning electron microscopy measurement. The effects of calcination temperature on the microstructure, piezoelectric and ferroelectric properties were systematically investigated. The dielectric and electrical properties of Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 ceramics were measured from 1kHz to 1MHz at various calcination temperatures. We expect that an optimized calcination condition can improve the piezoelectric and ferroelectric properties of Ag doped 0.95(Na0.52K0.48)NbO3–0.05LiTaO3 lead-free piezoelectric ceramics.

Exceptionally large piezoelectric strains in BiFeO3–(K0.5Bi0.5)TiO3–PbTiO3 ceramics

Samples of (1−x−y)BiFeO3–x(K0.5Bi0.5)TiO3–yPbTiO3, where x = 0.15 and y = 0.275, were produced via a conventional mixed oxide method. Ceramics were characterized using X-ray diffraction, confirming an electric-field-induced phase change from predominantly rhombohedral to mixed phase tetragonal and rhombohedral structure upon poling. There was a remnant polarization of 34 μC cm−2 and a total strain of 0.805% at 6.5 kV mm−1, the highest electric-field-induced strain reported in a polycrystalline material. A d33 of 205 pm V−1 was measured and Rayleigh analysis was used to quantify the extrinsic contributions.

Microstructure and Piezoelectric Properties of (0.996-x) K&lt;sub&gt;0.5&lt;/sub&gt;Na&lt;sub&gt;0.5&lt;/sub&gt;NbO&lt;sub&gt;3&lt;/sub&gt; - 0.004 BiFeO&lt;sub&gt;3&lt;/sub&gt; - &lt;i&gt;x&lt;/i&gt; LiSbO&lt;sub&gt;3&lt;/sub&gt; Ceramics

(0.996-x) K0.5Na0.5NbO3- 0.004 BiFeO3- x LiSbO3 (x =0.00, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07) lead-free piezoelectric ceramics were prepared by the conventional mixed oxide method. The compositional dependence of the phase structure and the electrical properties of the ceramics were studied. A morphotropic phase boundary between the orthorhombic and tetragonal phases was identified in the composition range of 0.03 &lt; x &lt; 0.06. With the content of LS increases, the size of the pores significantly decreases. However, adding larger amount of LS makes the pore size increase slightly. The (0.996-x)KNN-0.004 BF-xLS(x=0.05) ceramics possess good electrical properties: d33 = 280 pC/N, kp = 53.3%, Tc = 345 °C, εr = 1613, Tan δ =2.07%. These results show that the ceramic is a promising lead-free piezoelectric material.

Effect of sintering temperature on internal‐bias field and electric properties of 0.2PZN–0.8PZT ceramics

AbstractPiezoelectric ceramics system of Pb((Zn1/3Nb2/3)0.20–(Zr0.50Ti0.50)0.80)O3 (0.2PZN–0.8PZT) was prepared by the conventional oxide mixing method. The dependences of the internal‐bias field and electric properties on the sintering temperature were investigated systematically. The results indicated that the perovskite structure was stable in a wide sintering temperature region. The rise of sintering temperature favored the enlargement of the grain size, while showing a slight effect on tetragonal distortion c/a. The dissymmetrical shape of polarization–electric field hysteresis loops was displayed in all specimens, indicating the existence of internal‐bias field (Ei). With the increase of sintering temperature, Ei sharply decreased to 0.84 kV cm−1 at 1000 °C then increased, while the remnant polarization (Pr) was found to show the inverse trend. The derivative effects of the sintering temperatures, involving the internal‐bias field effect and grain‐size effect, affected the ferroelectric and piezoelectric properties of 0.2PZN–0.8PZT.