Conventional Mixed Oxide Method Research Articles

Fabrication and evaluation of Pb(W0.5Cu0.5)O3 modified PLZT piezoelectric ceramics

In this paper, we report the fabrication and evaluation of novel piezoelectric ceramics based on modification of Pb0.9025La0.065(Zr0.58Ti0.42)0.975Nb0.02O3 (PLZT) with Pb(W0.5Cu0.5)O3 (PWC). First, PWC was mixed with PLZT in suspensions at various concentrations (0–10wt%) using conventional mixed-oxide method and then sintered at temperature ranging from 950–1150°C. The resultant samples of PWC-modified PLZT ceramics were subsequently evaluated for the effects of PWC doping on the microstructure, piezoelectric and dielectric properties, and sintering temperature of the PLZT ceramics. It was observed that doping with PWC generally promoted the sintering conditions, and thus greatly influenced the electric properties including piezoelectric constant d33, dielectric permittivity εr and electromechanical coefficient kp of the modified PLZT ceramics. Taken together, the results indicate that the optimal sintering condition for PWC-modified PLZT ceramics was estimated to be at 1150°C with PWC doping at 4wt%. Consequently, the PWC-modified PLZT may potentially provide an excellent piezoelectric ceramics for manufacturing ultrasonic sensors and capacitors.

Effect of grain size on the phase structure and electrical properties of PZT–PNZN quaternary systems

The quaternary systems 0.74Pb(Zr0.47Ti0.53)O3–0.26Pb[(Ni0.6Zn0.4)1/3Nb2/3]O3(PZT–PNZN) have been prepared using the conventional oxide mixing method in a wide temperature region between 1050 and 1250°C. All specimens present high relative density above 95%, indicating a wide sintering window for this system. Investigation of the microstructure reveals a continuous increase in grain size from 1.07 to 2.77μm when the sintering temperature is increased from 1050 to 1250°C, which obeys the common grain-growth law well. However, unlike compositional component PZN–PZT and PNN–PZT, the phase structure of quaternary PZN–PNZN is not sensitive to the grain size. The specimens with different grain size retain the morphotropic phase boundary (MPB) structure and the size induced phase transition does not appear. Excluding the influence of the phase structure, the size effect plays a dominant role in improving the piezoelectric properties, which facilitates the motion of domain walls due to the decreasing number of grain boundary. The optimum piezoelectric parameters are obtained at 1150°C: d33=307pC/N, kp=0.56.

Phase structure and the dielectric properties of the (Zn, Mg)2(Ti, Sn)O4 ceramics

(1−x)ZnO–xMgO–0.88TiO2–0.12SnO2 (x=0.05, 0.10, 0.15 and 0.20) ceramics were prepared by conventional mixed-oxide method. The phase structure, morphology and dielectric properties of the ceramics were investigated. The results show that Mg was incorporated into the phase of Zn2(Ti,Sn)O4 and the spinel-type solid solution (Zn(1−x),Mgx)2(Ti0.88,Sn0.12)O4 formed, the solid solubility limit of Mg was situated at x=0.05–0.10. The 0.95ZnO–0.05MgO–0.88TiO2–0.12SnO2 ceramics sintered at 1080°C exhibit dielectric properties εr=18.9, tanδ=5.5×10−4 and near zero temperature coefficient of dielectric constant (τε=2.89ppm/°C). Due to their stable dielectric property, the 0.95ZnO–0.05MgO–0.88TiO2–0.12SnO2 ceramics can serve as the promising high-frequency dielectric capacitor after further modification.

Investigation of phase diagram and electrical properties of xPb(Mg1/3Nb2/3)O3–(1 − x)Pb(Zr0.4Ti0.6)O3 ceramics

Ceramics in PMN–PZT system with formula xPb(Mg1/3Nb2/3)O3–(1 − x)Pb(Zr0.4Ti0.6)O3 (where x = 0.32, 0.35, 0.38, 0.41) were prepared by the conventional oxide-mixed method. The phase diagram, composition dependent ferroelectric, dielectric, field-induced strain and piezoelectric properties were systematically investigated. X-ray diffraction analysis indicated that as-prepared ceramics were of pure perovskite phase and the possible morphotropic phase boundary (MPB) between the tetragonal and pseudo-cubic phase compositions were located near the PMN content of x = 0.38, confirmed by their corresponding ferroelectric, dielectric, field-induced strain and piezoelectric properties. The composition with x = 0.38 possessed the optimum electrical properties since its composition locate close to the MPB where exist multiple polarization directions facilitates domain reorientation and consequently enables the superior electrical properties. The room temperature dielectric permittivity er, tangent loss tan δ, piezoelectric coefficient d33, electromechanical coupling factor kp, remnant polarization Pr, hysteresis loop squareness Rsq and longitudinal strain of 0.38PMN–0.62PZT ceramics are 2441, 2.08 %, 662 pC/N, 63.5 %, 37.2 μC/cm2, 1.51 and 1.9 ‰, respectively, which mean it has a great promise for actuator applications.

Dielectric properties of Ag-doped 0.94(K0.5Na0.5)NbO3-0.06LiNbO3 ceramics prepared by templated grain growth

We have investigated the relaxation mechanism and dielectric properties of Ag-doped 0.94(K0.5Na0.5)NbO3-0.06LiNbO3 lead-free piezoelectric ceramics prepared by the templated grain growth method using cubic (K,Na)NbO3 single crystal seeds as templates. Specimens were prepared by the conventional mixed oxide method and sintered in a controlled atmosphere. Since the templated grain growth method can increase the grain size by introducing the templates, the dielectric properties of the ceramics were improved. Various dielectric experiments were carried out to obtain information about the possible relaxation behavior and activation energies of the ceramics. Cole–Cole plots were made to investigate the relaxation mechanisms of the grains and grain boundaries in Ag-doped 0.94(K0.5Na0.5)NbO3-0.06LiNbO3 ceramics.

Structural and electrical properties of 1 − x(Na0.5K0.5)NbO3–x(Sr0.5Ca0.5)TiO3 ceramics

In this study, 1−x(Na0.5K0.5)NbO3–x(Sr0.5Ca0.5)TiO3 ceramics were fabricated using the conventional mixed oxide method. The effects of the addition of (Sr0.5Ca0.5)TiO3 on the structural and electrical properties of the specimens were investigated for their application in piezoelectric devices. As the results of X-ray diffraction analysis show, all specimens display the typical polycrystalline perovskite structure without the presence of the second phase. Sintered densities increased with an increase in the amount of (Sr0.5Ca0.5)TiO3 added and the specimen with 0.08mol% of (Sr0.5Ca0.5)TiO3 added showed the maximum value of 4.54g/cm3. Both average grain size and densification increased with an increase in the amount of (Sr0.5Ca0.5)TiO3. The electromechanical coupling factor, dielectric constant ϵr, dielectric loss tan δ, d33 and Curie temperature of the 0.92(Na0.5K0.5)NbO3–0.08(Sr0.5Ca0.5)TiO3 specimens doped with 0.08mol% of (Sr0.5Ca0.5)TiO3 were 0.31, 1338, 0.021, 138 and 445°C, respectively.

Compositional Range and Electrical Properties of Lead-Free Bi0.5(Na0.8K0.2)0.5TiO3-(Ba0.98Nd0.02) TiO3 System

Lead-free piezoelectric ceramics (1−x)Bi0.5(Na0.8K0.2)0.5TiO3-x(Ba0.98Nd0.02)TiO3 or (1−x)BNKT-xBNdT (x = 0.05–0.15 mol fraction) were synthesized by conventional mixed-oxide method. All samples had relative densities more than 98% of theoretical values. All compositions had pure perovskite structure and BNdT effectively diffused into BNKT lattice during sintering to form solid solutions. Grain size and shape were slightly affected by BNdT addition. The addition of BNdT into BNKT was also found to affect dielectric, ferroelectric and piezoelectric performances with the maximum values (Tm = 328°C, ϵr = 1736, tanδ = 0.0714, Pr = 21.91 μC/cm2, d33 = 228 pC/N) observed in 0.89BNKT-0.11BNdT composition.

Effects of Dopants on Phase Formation and Microstructure of Bismuth Sodium Titanate-Potassium Sodium Niobate Ceramics

In this work, the solid solution of (0.93)(Bi0.5Na0.5)TiO3-(0.07)(K0.5Na0.5)NbO3 ceramics were prepared by a conventional mixed-oxide method. The influence of 0.5 mol% MnO2, Sb2O5 and Li2O3 addition on phase formation, microstructure and dielectric properties of BNT-KNN has been investigated. It was found that the BNT-KNN ceramics exhibited the perovskite structure with pseudo-cubic symmetry. The microstructure showed grain shape depending additive; the pure BNT-KNN the round shape grains were seen, while with the oxide additive square or rectangular shape grains appeared. The oxide addition into BNT-KNN ceramics resulted in the difference dielectric properties and Curie temperatures.

소결온도 변화에 따른 (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3세라믹스의 유전 및 압전 특성

(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 + 0.04 wt% CeO2 lead-free ceramics were prepared by conventional oxide-mixed method and the effect of sintering temperature on microstructure, dielectric and piezoelectric properties were investigated. Improved piezoelectric properties have been observed at 1,400°C sintering temperature which show the optimal electrical properties, kp∼0.412, d33∼316 pC/N, Qm∼144, er∼3,345 and Tc∼85°C. These results show that the sintering temperature plays an important role in piezoelectric properties.

The Influence of Fabrication Conditions on the Physical Properties of PLZT:Nd3+ Ceramics

Abstract The aim of this work was to study the effect of fabrication conditions and neodymium co-doping on the physical properties of (Pb0:98La0:02)(Zr0:65Ti0:35)0:98O3, known as PLZT:Nd3+ ceramics. All ceramic powders of these materials were synthesized by the conventional mixed oxide method, from the high purity raw materials (>99.9%). The bulk ceramic samples were sintered by the pressure less sintering and the hot-uniaxial pressing techniques. The study gives a detailed account of the relationships between doping and preparing conditions on the dielectric and optical properties of obtained ceramic materials. Optimal conditions of PLZT:Nd3+ preparation as well as Nd3+ activator concentration were determined in relation to the potential opto-electronic applications.

Synthesis, Microstructure and the Crystalline Structure of the Barium Titanate Ceramics Doped with Lanthanum

Abstract In the present study BaTiO3 and Ba1-xLaxTiO3 (0.1-0.4mol.% La) ceramic powders were synthesized by the conventional mixed oxide method (MOM). The characterization of the ceramic powders was carried out using a simultaneous thermal analysis (STA), with a combined DTA/TG/DTG system (Netzsch STA409). The results of thermal analysis allowed to determine the optimal temperature of synthesis. Microstructure was investigated by scanning electron microscopy (SEM), crystalline structure was studied by X-ray diffraction method (XRD). The EDS investigations showed that samples exhibited conservation of stoichiometry according to the chemical composition formula. The X-ray diffraction analysis confirmed formation of the desired crystalline structure both pure and La3+-doped BaTiO3 ceramics exhibiting a perovskite-type structure ABO3 with tetragonal symmetry P4 mm.

A study of effects of sintering on the piezoelectric properties of 0.97(K0.5Na0.5)NbO3-0.03(Bi0.5Na0.5)TiO3 lead-free ceramics

As a candidate for a lead free-piezoelectric material, the 0.97(K0.5Na0.5)NbO3-0.03(Bi0.5Na0.5)TiO3 ceramic was prepared by using the conventional mixed-oxide method. 0.97(K0.5Na0.5)NbO3-0.03(Bi0.5Na0.5)TiO3 ceramics were investigated to determine the effect of the sintering temperature. The crystal structures of 0.97(K0.5Na0.5)NbO3-0.03(Bi0.5Na0.5)TiO3 lead-free piezoelectric ceramics were examined by varying the sintering temperatures from 1080 °C to 1160 °C and employing an X-ray diffraction analysis and scanning electron microscopy measurements. The effects of the sintering temperature on the microstructure, piezoelectric and ferroelectric properties were systematically investigated. The dielectric and the electrical properties of the 0.97(K0.5Na0.5)NbO3-0.03(Bi0.5Na0.5)TiO3 ceramics were measured at frequency from 1 kHz to 100 kHz and at various sintering temperatures. We expect optimized sintering characteristics to improve the piezoelectric and the ferroelectric properties of 0.97(K0.5Na0.5)NbO3-0.03(Bi0.5Na0.5)TiO3 ceramics.

Enhancement of the dielectric, piezoelectric, and ferroelectric properties in BiYbO3-modified (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 lead-free ceramics

Lead-free (1−x)(Ba0.85Ca0.15)(Ti0.9Zr0.1)O3−xBiYbO3 [(1−x)BCTZ−xBYO] piezoelectric ceramics in the range of BYO concentrations were prepared by the conventional oxide-mixed method, and the effect of BYO content on their microstructure, crystalline structure, density and electrical properties was investigated. A dense microstructure with large grain was obtained for the ceramics with the addition of BYO. The ceramics with x=0.1% exhibit an optimum electrical behavior of d33~580pC/N, r~10.9Ω, kp~56.4%, and tanδ~1.12% when sintered at a low temperature of ~1350°C. When the measuring electric field is 40kV/cm, the well-saturated and square-like P–E loops for the ceramics were observed with Pr~12.2μC/cm2 and Ec~1.83kV/cm.

Magnetoelectric Properties of BaTiO<sub>3 </sub>– Co<sub>0.5</sub>Ni<sub>0.5</sub>Fe<sub>2</sub>O<sub>4</sub> Composites Prepared by the Conventional Mixed Oxide Method

Multiferroics, which display simultaneous ferrimagnetic and ferroelectric properties, have been interesting recently because of their potentially significant applications in multifunctional devices such as magnetic resonance, drug delivery, high-density data storage, ferrofluid technology, etc. Composites combining BaTiO3 with Co0.5Ni0.5Fe2O4 have influenced the interest of many researchers, due to their outstanding and distinguished character called magnetoelectric (ME). In this work, ferrimagnetic-ferroelectric composites of BaTiO3 nanopowder and Co0.5Ni0.5Fe2O4 nanopowders were prepared by a conventional mixed oxide method. The multiferroic ceramics were compounded with the formula, (1-x)BaTiO3-(x)Co0.5Ni0.5Fe2O4, in which x = 0, 0.05, 0.10, 0.20 and 0.35. All of the compositions were analyzed by an X-ray diffractometer (XRD) in order to reveal the phase of perovskite and spinal structure. Scanning electron microscopy (SEM) was used to examine the variation of morphology and grain size of the composited ceramics. The magnetism of all the ceramics was measured using a vibrating sample magnetometer (VSM). The results showed that microstructure and the amount of ferrite are related strongly with magnetization.

Transmission Electron Microscopy of Mn-doped KNN Ceramics

Smart materials like piezoelectrics and ferroelectrics play a crucial role in applications such assensors and actuators,radio-frequency switching, drug delivery, chemicals detection, and power generation and storage. K0.5Na0.5NbO3 (KNN) is one of the leading lead free piezoelectric materials being considered as an alternativeto Pb(Zrx,Ti1-x)O3 (PZT), which is currently the most widely used material for electromechanical applications. Although pure KNN has inferior electromechanical properties compared to PZT,efforts are on going to tailor and improve its piezoelectric coefficients by doping and texturing.Although the piezoelectric constant (d33) of undoped KNN is unsuitable for practical electromechanical applications, properties comparable to PZT at room temperature (d33>400 pC/N) have been reported for modified KNN ceramics. Electromechanical properties are however, very much dependent on the crystalline phase content, crystallographic orientation, microstructure, interfaces and domain configuration.Mn is an indispensable dopant for both PbO-based as well as PbO-free ceramics like BaTiO3, SrTiO3, KNbO3 and KTaO3. It has been reported to improve the density, mechanical quality factor, electromechanical properties and to reduce dielectric loss. Mn has been successfully used to reduce the leakage current and lower the orthorhombic to tetragonal phase transition temperature (TO-T) in KNN single crystals. It has also been shown to improve the density and properties of KNN–LiTaO3–LiSbO3. However, the effect of Mn on the KNN domain structure and phase assemblage has not yet been reported. In this work, KNN ceramics doped with Mn on the B-site (Mn content was 0.5, 1.0. 1.5 and 2 mole%) were synthesized by a conventional mixed oxide method. Transmission electron microscopy (TEM)(Hitachi 9000) studies were carried out to analyse the effect of B-site Mn doping on the ferroelectric domain structure and phase assemblage.Undoped KNN ceramics had large grains (>30 >m) which contained large (>1 >m wide) wedge shaped ferroelectric domains. KNN doped with 0.5 mole % Mn exhibited a smaller grain size (~2 mm) in which a well defined domain structure was observed with widths approximately an order of magnitude smaller than those in undoped KNN. For KNN doped with 2 mole % Mn, the presence of a second phase, Figure 1c, was often observed. Electron diffraction patterns from the second phase were consistent with a tetragonal tungsten bronze (TTB) structured compound although more work is required to definitively determine the phase assemblage. The domain structure became increasing complex as Mn concentration increased, suggesting that the presence of Mn on the B-site disrupts polar order.In conclusion, TEM analysis demonstrated that Mn doping changes the domain structure of KNN ceramics: for low Mn content, well defined ferroelectric domains and for high Mn content, tangled domains and second phase were the main features.These microstructure details elucidate reasons that may account for the inferior piezoelectric properties of KNN at higher Mn concentration.

Phase Structure, Microstructure and Electrical Properties of Lead-Free (1-x) [Na<sub>0.515</sub>K<sub>0.485</sub>]<sub>0.94</sub>Li<sub>0.06</sub>(Nb<sub>0.99</sub>Ta<sub>0.01</sub>)O<sub>3 - </sub>BiAlO<sub>3</sub> Ceramics

Lead-free (1-x)[(Na0.515K0.485)0.94Li0.06(Nb0.99Ta0.01)O3]-xBiAlO3 (NKLNT-BA; x = 0, 0.005, 0.010, 0.015, and 0.020) ceramics were fabricated by a conventional mixed-oxide method. The effects of BiAlO3 addition on the phase structure, microstructure and electrical properties of ceramic were then studied. The result indicated that grain size decreased with increasing of BiAlO3 content. In the composition range studied, the perovskite phase with the coexistence of the orthorhombic and tetragonal phases was identified at approximately x 0.005 by the X-ray diffraction analysis and dielectric spectroscopy, which led to a significant enhancement of the piezoelectric properties. The tetragonality increased with further increasing x. The temperature dependence of dielectric properties showed that the addition of BiAlO3 slightly decreased the ferroelectric tetragonal-paraelectric cubic phase transition temperature (TC), but greatly shifted the polymorphic phase transition from the ferroelectric orthorhombic to the ferroelectric tetragonal phase (TOT) to lower room temperature. The dielectric and piezoelectric properties are enhanced for the composition near the orthorhombic-tetragonal polymorphic phase boundary. The unmodified-(Na0.515K0.485)0.94Li0.06(Nb0.99Ta0.01)O3 ceramics exhibit optimum electrical properties (d33 = 225 pC/N and TC = 418°C).

Effect of composition on electrical properties of lead-free Bi0.5(Na0.80K0.20)0.5TiO3-(Ba0.98Nd0.02)TiO3 piezoelectric ceramics

Lead-free piezoelectric ceramics with the composition of (1−x)Bi0.5(Na0.80K0.20)0.5TiO3-x(Ba0.98Nd0.02)TiO3 or (1−x) BNKT-xBNdT (with x = 0–0.20 mol fraction) have been synthesized by a conventional mixed-oxide method. The compositional dependence of phase structure and electrical properties of the ceramics were systemically studied. The optimum sintering temperature of all BNKT-BNdT ceramics was found to be 1125 °C. X-ray diffraction pattern suggested that BNdT effectively diffused into BNKT lattice during sintering to form a solid solution with a perovskite structure. Scanning electron micrographs showed a slight reduction of grain size when BNdT was added. It was found that BNKT-0.10BNdT ceramic exhibited optimum electrical properties (εr = 1716, tanδ = 0.0701, Tc = 327 °C, and d33 = 211 pC/N), suggesting that this composition has a potential to be one of a promising lead-free piezoelectric candidate for dielectric and piezoelectric applications.

Phase Structure, Microstructure and Electrical Properties of BiMnO<sub>3</sub>-Doped (Na<sub>0.515</sub>K<sub>0.485</sub>)<sub>0.96</sub>Li<sub>0.04</sub>(Nb<sub>0.8</sub>Ta<sub>0.2</sub>)O<sub>3</sub> Lead-Free Ceramics

1-x)[(Na0.515K0.485)0.96Li0.04(Nb0.8Ta0.2)O3]-xBiMnO3 (x = 0, 0.002, 0.004, 0.006, 0.008 and 0.010) lead-free ceramics were prepared using a conventional mixed-oxide method. The result indicated that the highest density of 4.89 ± 0.01 g/cm3 was found in 0.6 mol% BiMnO3 - doped sample sintered at 1060 C. Grain size decreased with increasing of BiMnO3 content. In the composition range studied, the perovskite phase with the coexistence of the orthorhombic and tetragonal phases was identified at approximately 0 x 0.006 by the X-ray diffraction analysis, which led to a significant enhancement of the piezoelectric properties. The temperature dependence of dielectric properties showed that the addition of BiMnO3 markedly decreased the ferroelectric tetragonal-paraelectric cubic phase transition temperature (TC), and greatly shifted the polymorphic phase transition from the ferroelectric orthorhombic to the ferroelectric tetragonal phase (TOT) to near room temperature. Sample with x = 0.002 exhibited excellent electrical properties: the dielectric constant (er) = 1228, dissipation factor (tan δ) = 0.0244, piezoelectric constant (d33) = 235 pC/N, and Curie temperature (TC) = 286 °C. These results clearly showed that the 0.998(Na0.515K0.485)0.96Li0.04(Nb0.8Ta0.2)O3 - 0.002BiMnO3 ceramics are very promising lead-free piezoelectric candidates.

Composition range and electrical properties of the morphotropic phase boundary in Bi0.5(Na0.80K0.20)0.5TiO3-(Ba0.7Sr0.3)TiO3 system

The lead-free piezoelectric ceramic binary system of (1-x)Bi0.5(Na0.80K0.20)0.5TiO3-x(Ba0.7Sr0.3)TiO3 or (1-x) BNKT-xBST (with x ranging from 0.05 to 0.15 mol fraction) near the morphotropic phase boundary (MPB) has been investigated. The ceramics were synthesized by a conventional mixed-oxide method and sintered at 1125°C for 2 h. All BNKT-BST samples had relative density higher than 98% of their theoretical values. X-ray diffraction patterns showed that all compositions had a pure perovskite structure and BST effectively diffused into the BNKT lattice during sintering to form a solid solution. Crystal structure changed from rhombohedral-rich phase to tetragonal-rich phase with increasing BST content. Because of such MPB-like behavior, the highest dielectric (Tc = 325°C, ɛr = 1827, tan δ = 0.0823) and piezoelectric performances (d33 = 225 pC/N) were obtained in the BNKT-0.11BST sample.

Structural, ferroelectric and piezoelectric properties of Mn-modified BiFeO3–BaTiO3 high-temperature ceramics

Mn modified BiFeO3–BaTiO3 (abbreviated as BFBT-Mnx%, x = 0.1, 0.3, 0.6, 0.9, 1.2) high-temperature lead-free ceramics were prepared by conventional oxide-mixed method and the effect of Mn doping on microstructure and electrical properties was investigated. The solid solutions show a single phase perovskite structure, and the content of Mn has a significant effect on the microstructure of ceramics. The addition of Mn can induce combinatory “hard” and “soft” piezoelectric characteristics due to aliovalent substitutions. In particular, x = 0.6 BFBT-Mnx% ceramic, with a Curie temperature, T c, of ~463 °C, shows optimum piezoelectric properties of d 33 = 131pC/N, k p = 0.298. The simultaneous existence of good piezoelectric properties and high T c makes these ceramics suitable for elevated temperature piezoelectric devices.