An electron microscopic investigation of grain boundary phenomgna in 8/65/35 PLZT ceramics

A detailed investigation of microstructure in abnormal crystal grain boundary (GB) migration regions was carried out by TEM and STEM+EDS. It was shown that the crystal orientation of those regions swept over by the migrated grain boundaries (MGBs) are readjusted as compared with their parent grains. Strain induced β-phase is confirmed around those regions as Well.     

Electrical creep around a circular hole in PLZT 8/65/35

The strain-birefringence correlation was exploited to study the local behaviour near a circular hole in unpoled PLZT 8/65/35 under electric field below than the coercive field. The observed birefringence contours near the hole show a spatial distribution and time dependence. Due to the enhancement of electric field near the hole, the polarization creep rate is greatly increased. The evolution of the local principal strain difference with time and position in the sample is quantified. Overall, an accelerated poling effect is found in comparison with the behaviour under uniform field. This appears to be due to inhomogeneous field distribution which initiates polarization switching in areas of locally enhanced electric field. The presence of the hole promotes a nearly linear growth in average polarization with time, despite the strongly nonlinear response of the parent material. The results indicate that insulating porosity can strongly affect the switching behaviour and coercivity of ferroelectric ceramics.     

A Novel Mechanism for Relaxor–Ferroelectric Transition in PLZT(8/65/35)

We report a novel mechanism for the spontaneous transition to the ferroelectric (FE) phase in a typical relaxor, PLZT(8/65/35). Dielectric, FE, induced strain, and structural studies reveal the influence of acceptor dopant Cu²⁺ on this transition. That this transition occurs under zero-field conditions reveals yet another challenge in the use of copper metal electrodes for PLZT-based thin-film devices.     

Influence of synthesis process on the AC response of PLZT (8/65/35) ferroelectric ceramics

AC conductivity measurements have been carried out to study the dielectric characteristics of a ferroelectric PLZT (8/65/35). The initial powders were synthesized by two different methods: conventional mixed oxides and a chemical coprecipitation method. In both cases, the final ceramic bodies were obtained by an uniaxial hot-pressing step. The grain and grain boundary responses have been separated and a mixture of ionic-electronic conductivity was evaluated from the Arrhenius dependence. The preparation techniques led to different absolute conductivity values for each contribution (grain, σ_g, or grain boundary, σ_gb). The samples prepared by the mixed oxide method (MO) showed a higher bulk conductivity than those prepared by the coprecipitation method (CP). This result was explained taking into account the different concentration of charge carriers in MO than CP samples, influenced by the PbO content in the grain boundary. The dielectric analyses showed classical ordinary relaxor-dielectrics with a diffuse phase transition, which was markedly larger in the oxide-milled method (MO). The conductive mechanisms and their influence on the dielectric behavior were studied and led to the conclusion that they affect the dielectric permittivity measurements. The dielectric permittivity without the conductivity component showed a phase transition with lower dispersion for both preparation techniques.     

Effects of Preparation Conditions on the Structural and Optical Properties of Spark Plasma-Sintered PLZT (8/65/35) Ceramics

Transparent lanthanum-doped lead zirconate titanate (PLZT) ceramics with high density were fabricated using spark plasma sintering (SPS), a recently developed hot-pressing method. A wet–dry combination method was used to prepare the fine PLZT powders. The average grain size of the PLZT ceramics was less than 1 μm, because of a relatively low sintering temperature and a very short sintering time. The transmittance of PLZT ceramics increased with an increase of calcination temperature up to 700°C and then it slightly decreased with further increase of calcination temperature. The transmittance strongly depended on the SPS temperature and heat-treatment temperature. The pellet sintered at 900°C for 10 min and heat treated at 800°C for 1 h with a thickness of 0.5 mm showed a transmittance of 31% at a wavelength of 700 nm. The relationships between the transmittance and the microstructure were investigated.     

Dielectric,ferroelectric and induced strain behavior of PLZT 9/65/35 ceramics modified by Bi2O3 and CuO co-doping

PLZT 9/65/35 (Pb_0.91La_0.09(Zr_0.65Ti_0.35)_0.9775O₃) ceramics with addition of 0.25, 0.5 and 1.0 wt% of Bi₂O₃/CuO (where the ratio of Bi₂O₃:CuO=9:1 by mole) were prepared by sintering at the temperatures between 1000 and 1200 °C. It was found that Bi₂O₃/CuO could bring the sintering temperature down ~50 °C to obtain PLZT with no second phase. Dielectric and ferroelectric properties were investigated. Bi₂O₃/CuO decreased both coercive field and remnant polarization, which was caused by an increase of the degree of diffuseness in relaxor ferroelectric materials. Electric field induced strain behavior was also investigated and it was found that the addition of Bi₂O₃/CuO increased the maximum induced strain and maximized electrostrictive effect. Therefore, Bi₂O₃/CuO was useful as a sintering aid, which improved the dielectric and the relaxor ferroelectric properties as well as the electric field induced strain of PLZT ceramics.     

Study of aging behavior of 9/70/30 and 9/65/35 PLZT by optical interferometric technique

In this work Pb_0.91La_0.09(Zr_0.70Ti_0.30)_0.9775O₃ PLZT (9/70/30) and Pb_0.91La_0.09(Zr_0.65Ti_0.35)_0.9775O₃ PLZT (9/65/35) ceramics were prepared at four different sintering temperatures by solid solution method. The samples were aged by keeping at room temperature for 19 days. After the aging process, structural and electrical properties of the samples were studied using Modified Michelson Interferometer, LCR meter and X-ray diffraction. The effect of the Zr/Ti ratios on the dielectric and ferroelectric properties was also investigated. The aged PLZT (9/70/30) showed pinched P–E loop and remnant strain in rhombohedral phase, while PLZT (9/65/35) showed distort s–E shape implying non-180° domain in tetragonal phase.     

Effect of Li and Bi co-doping and sintering temperature on dielectric properties of PLZT 9/65/35 ceramics

In the present study, lead-lanthanum-zirconate-titanate (PLZT) ceramics were prepared by a solid-state mixed oxide method. Different amount of lithium carbonate and bismuth oxide (0.15 mol%, 0.45 mol% and 0.75 mol%), where the ratio of Li:Bi =1:1 by mole, was added to PLZT to investigate the effect of Li and Bi co-doping. The ceramic samples were sintered at the temperatures of 1000, 1050, 1100, 1150 and 1200 °C for 4 h. After that, all samples were subjected to phase identification, physical property determination (sintered density and microstructure) and dielectric property measurement. It was found that doping of 0.15 mol% Li and Bi resulted in maximum dielectric constant (ε_r =7819) when sintered at 1200 °C. Grain size of PLZT ceramics was dependent on sintering temperature and dielectric properties were affected by the chemical composition rather than the grain size of the ceramics. Therefore, co-doping of Li and Bi was useful as it could improve the dielectric properties of PLZT ceramics.     

Lanthanum Dependence of Elastic and Piezoelectric Properties of PLZT Ceramics with a Zr/Ti Ratio of 65/35

The elastic and piezoelectric properties of PLZT ceramics with a 65/35 Zr/Ti ratio undergo pronounced changes as La is added to the structure. At the rhombohedral-tetragonal phase boundary, material constants plotted as functions of La concentration show strong discontinuities in slope; these discontinuities provide a precise means of locating the boundary. The radial-mode coupling factor, k_p , compliance coefficient, S₁₁ ^E , and piezoelectric coefficient, d₃₁ , attain peak values at the boundary, whereas Poisson's ratio, σ^E, and the resonance-frequency constant exhibit pronounced minima. This behavior is evidence of the increasing ferroelastic sensitivity of the material as the distortion angle of the rhombohedral phase approaches a minimum.     

Influence of low external magnetic field on electric field induced strain behavior of 9/70/30, 9/65/35 and 9/60/40 PLZT ceramics

In this work, Pb_0.91La_0.09(Zr_xTi_1−x)_0.9775O₃ PLZT ceramics, where x =0.70, 0.65 and 0.60, were prepared by a solid-state mixed-oxide technique. Structural information was investigated by X-ray diffraction method. Electric field induced polarization and strain behavior of the PLZT ceramics under an influence of static magnetic field were measured by a Sawyer-Tower circuit in conjunction with Michelson interferometer at various static magnetic fields (0–30.7 mT). The results showed that the imposed magnetic field affected the polarization and induced strain behaviors in PLZT ceramics More interestingly, the imposed magnetic field showed more significant influence on the PLZT ceramic composition near morphotropic phase boundary (MPB), i.e. PLZT 9/65/35. The spontaneous polarization of 180° domain switching was seen to be suppressed by the applied magnetic field.     

Dielectric,pyroelectric and ferroelectric behavior of PZTN 65/35/x ferroelectric ceramic system

Niobium doping lead zirconate titanate [PZTN 65/35/x (x = 1, 2, 4, 5)] ferroelectric ceramics show perovskite structure and a rombohedral phase. The average grain size, the maximum dielectric permittivity, the transition temperature and the remanent polarization decrease when the niobium concentration increases, while the coercive field does not show any particular behavior and the porosity increases. The results are discussed taking into account the incorporation of the niobium to the lattice and the variation of the grain size. Preliminary results of the pyroelectric behavior are shown.     

La掺杂对PLZT压电陶瓷及PLZT/PVDF复合材料结构及特性的影响

分别采用固相反应烧结法和注模法制备（Pb1-xLax）（Zr0.5Ti0.5）1-x/4O3（x=0.01～0.13）锆钛酸铅镧（lead lanthanum zironate titanate,PLZT）压电陶瓷和0-3型PLZT/聚偏二氟乙烯（polyvinylidene fluoride,PVDF）复合材料。用X...     

PP/EPR/纳米CaCO3三元共混体系的研究

采用双辊混炼和挤出制样的方法制备了PP／EPR／纳米CaCO3复合材料。采用扫描电镜(SEM)、透射电镜(TEM)对复合材料进行了断面观察，并测试了复合材料的力学性能。结果表明，对纳米CaCO3进行表面改性和用适当的共混方法，可以显著提高复合材料的冲击强度。对复合材料冲击断面进行SEM观察时发现，材料发生了韧性断裂。     

Electrostrictive and Dielectric Response in Lead Magnesium Niobate–Lead Titanate (0.9PMN · 0.1PT) and Lead Lanthanum Zirconate Titanate (PLZT 9.5/65/35) under Variation of Temperature and Electric Field

In situ measurements of electrostrictive strain and effective dielectric constant for two ferroelectric relaxor materials, lead magnesium niobate–lead titanate (0.9PMN · 0.1PT) and lead lanthanum zirconate titanate (PLZT 9.5/65/35), were performed in the temperature ranges near their respective mean Curie points under the variation of applied electric field. The measurement results show that the polarization-related electrostrictive coefficients Q_ij are not constant under variation of temperature and electric field. The observed anomaly in Q_ij indicates the dynamic behavior of the existing micropolar domains and its coupling to local defect structure. The data also support the idea that at temperatures far above the mean Curie point, there is still a substantial amount of micropolar domain and the response of the relaxor materials at the experimental temperature range is from the combined contributions due to induced polarization and micropolar domain flipping.     

Hot-corrosion behavior of calcium-magnesium aluminosilicate melts on Ba1/3Sr1/3Ca1/3Al2Si2O8

Hot-corrosion behavior of Ba_1/3Sr_1/3Ca_1/3Al₂Si₂O₈ (BSCAS) in the presence of molten calcium-magnesium-aluminum-silicate (CMAS) is investigated in the temperature range of 1250–1350 °C. In comparison, the hot corrosion behavior of Ba_0.5Sr_0.5Al₂Si₂O₈ (BSAS) is also studied under the same conditions. The results indicate that CMAS corrosion of both BSCAS and BSAS is caused by the interdiffusion of Ba/Sr and Ca between CMAS and corroded samples. The presence of Ca cations in BSCAS lowers the diffusion driving force of Ca cations between CMAS and BSCAS, resulting in a reduced diffusion rate of Ca cations from CMAS into BSCAS. Moreover, the sluggish diffusion effect of multi-component cations hinders the outward diffusion of Ba/Sr cations from BSCAS. Thus, the BSCAS shows a better CMAS corrosion resistance than BSAS.     

Electrolytic loading of hydrogen in Zr65(Pd80Rh20)35 and Zr65Pd35 alloys prepared by mechanical grinding and in their oxidised derivatives

Zr₆₅(Pd₈₀Rh₂₀)₃₅ and Zr₆₅Pd₃₅ alloys were prepared by mechanical grinding of stoichiometric amounts of either ZrH₂ and Pd₈₀Rh₂₀ or ZrH₂ and Pd. Following a suggestion in the literature, these alloys were converted by thermal oxidation in air into the corresponding ZrO₂(Pd₈₀Rh₂₀) and ZrO₂Pd compounds, which are probably composed of Pd₈₀Rh₂₀ and Pd nanostructures embedded in ZrO₂.The aim of our work thereafter was to investigate hydrogen storage in these nanostructures. Both the alloys and their oxidation derivatives were thus loaded with hydrogen by cathodic reduction at 25 °C in 6 M KOH, and loaded hydrogen was then determined by anodic extraction. On comparing the hydriding extent of the alloys with that of the corresponding oxidation derivatives, the metal clusters which formed after thermal oxidation are probably much larger in PdRh than in Pd. The former exhibits the high decomposition pressure typical of massive Pd₈₀Rh₂₀ hydride, and the maximum [H]/[Pd_0.8Rh_0.2] atom ratio is ≈0.82. Conversely, the amount of hydrogen extracted from reduced ZrO₂Pd samples prepared in optimal conditions fits [H]/[Pd] atom ratios between 1 and 2. The shape of the electrochemical hydrogen desorption isotherms indicates that the hydrogen in excess of the β-Pd hydride phase is probably stored in a new, very stable form.     

纳米CaCO3/EPR/PP复合材料的冲击性能研究

采用双辊混炼和挤出制样的方法制备了纳米碳酸钙(CaCO3)／乙丙橡胶(EPR)／聚丙烯(PP)复合材料,研究了复合材料的冲击强度与试样放置时间的关系。结果表明,随着放置时间的增加,纳米CaCO3／EPR／PP复合材料的室温冲击强度提高,而未添加纳米CaCO3的EPR／PP复合材料的冲击强度则降低;纳米CaCO3用量为10phr试样,在放置一个月后,冲击强度达到50．3kJ／m2,比未添加纳米CaCO3的试样的冲击强度高86％。     

Polyaniline/FE3O4 magnetic nanocomposite prepared by ultrasonic irradiation

Ultrasonic irradiation is employed to assist the chemical oxidative polymerization of aniline in the presence of Fe₃O₄ nanoparticles in order to prepare a polyaniline (PANI)/Fe₃O₄ magnetic nanocomposite. In the chemical oxidative polymerization of aniline in the initially neutral medium, the optimum molar ratio of the oxidant ammonium persulfate to the monomer aniline is 2 : 1. The prepared PANI is in the emeraldine form and is doped by sulfate anions. Fe₃O₄ particles are encapsulated by PANI and dispersed well in PANI. Fe₃O₄ increases the doping level and decreases the crystallinity of PANI. The PANI/Fe₃O₄ nanocomposite possesses conductivity and magnetic properties. Increasing the Fe₃O₄ content increases the magnetization of the PANI/Fe₃O₄ composite but decreases its conductivity. © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 2107–2111, 2006     

Experimental investigation of Al2O3/8YSZ and CeO2/8YSZ plasma sprayed thermal barrier coating on diesel engine

In this research work, aluminium oxide/yttria stabilized zirconia (20%Al₂O₃/80%8YSZ) and ceria/yttria stabilized zirconia (20%CeO₂/80%8YSZ) were coated through atmospheric plasma spray technique (APS) as thermal barrier coating (TBC) over CoNiCrAlY bond coat on aluminium alloy (Al-13%Si) substrate piston crown material and their thermal cycling behavior were studied experimentally. Thermal cycle test of both samples were conducted at 800?°C. Microstructural, phase and elemental analysis of the TBC coatings were experimentally investigated. The performance, combustion and emission characteristics of Al₂O₃/8YSZ, CeO₂/8YSZ TBC coated and uncoated standard diesel engine were experimentally investigated. The test results revealed that CeO₂/8YSZ based TBC has an excellent thermal cycling behavior in comparison to the Al₂O₃/8YSZ based TBC. The spallation of the Al₂O₃/8YSZ TBC occurred mainly due to the formation of thermally grown oxide (TGO), and growth of residual stresses at top coating and bond coating interface. The experimental results also revealed that the increase of brake thermal efficiency and reduction of specific fuel consumption for both TBC coated engine. Further reduction of HC, CO and smoke and increase of NOx emission were recorded for both TBC coated engine compared to the standard diesel engine.