PLZT Powders Research Articles

Effect of Manganese Ion Diffusion on the Microstructural Evolution of Lead Lanthanum Zirconate Titanate Ceramic

Microstructural evolution of lead lanthanum zirconate titanate (PLZT) ceramics caused by diffusion of the Mn ion was observed. Specimens with layered structures were fabricated by copressing a PLZT powder (9/65/35) doped with Mn and same PLZT powder without the dopant. When the copressed specimen was sintered at 1200°C in air, the Mn ion diffused out of the doped region. The region originally containing the Mn ions was totally free of pores while all other regions remained porous. The formation of lattice vacancies, as a result of Mn diffusion, was attributed to the enhanced material transport and the resultant rapid densification.

Effect of Electrode Materials on Lead Lanthanum Zirconate Titanate with Heating under Reduced Atmosphere

To understand the ferroelectricity degradation of ferroelectric random access memory (FeRAM) capacitor under hydrogen atmosphere, reactions between lead lanthanum zirconate titanate (PLZT) and the electrode materials, such as platinum (Pt) and iridium oxide (IrO2), were investigated by thermal analysis. The PLZT powder was decomposed by heating under Ar+3%H2 atmosphere at 1000°C with lead (Pb) metal, PbO, ZrTiO4 and TiO2. The decomposed PLZT with Pb metal exhibited perovskite phase after annealing under air atmosphere at 1000°C and no pyrochlore phase was observed. We found that Pt reacted with the Pb precipitated from PLZT by heating under Ar+3%H2 atmosphere. Consequently, a large amount of PbPt alloy and a small amount of PtPb4 alloy were formed. The formation temperature of the alloys was lower than the decomposition temperature of PLZT without Pt. Pt was directly involved in the decomposition of PLZT. However, no alloys of Ir and Pb were formed in the mixture of PLZT and IrO2 under Ar+3%H2 atmosphere. The heat treatment of the mixture of PLZT and the electrode powders indicated that Pt promoted the decomposition of PLZT under Ar+3%H2 atmosphere and IrO2 reduced the rate of the decomposition.

Effects of annealing on the crystallization and roughness of PLZT thin films

Lead lanthanum zirconate titanate (PLZT) thin films with stoichiometry (9/65/35) were prepared by a dip-coating process using a polymeric organic solution. The solution viscosity was adjusted in the range of 15–56 cP. Silicon (100) substrates were previously cleaned and then immersed in the solution. The withdrawal speed of substrate from the solution was adjusted within a range of 5–20 mm/min. The coated substrates were thermally treated in the 450–700°C temperature range. Surface roughness and crystallization of these films are strongly dependent on the annealing conditions. Infrared and X-ray diffraction data for PLZT powders heat-treated at 650°C for 3 h show that the material is free of carbonate phases and crystalline.

Preparation of 9.5/65/35 PLZT Powders by Organic Precursor Method

Preparation of 9.5/65/35 PLZT Powders by Organic Precursor Method

PZT/PLZT ceramics prepared by hydrolysis and condensation of acetate precursors

Titanyl zirconyl acetate was prepared by chelating titanium isopropoxide with acetic acid, and was used as a precursor in a sol-gel process to obtain PZT and PLZT powders. The combined results of the DTA/TGA, FTIR and SEM studies indicate that the PLZT-precursor contained a higher mol fraction of acetate groups and that polycondensation was slower, resulting in a small particle size for the PLZT powder. X-ray photoelectron spectroscopy (XPS) was used to detect Ti oxidation states on the surface of the PZT and PLZT bulk ceramics sintered at various temperatures. The Ti binding energy of the PLZT powders prepared at various temperatures were all lower than those of the corresponding PZT powders, indicating a relatively higher Ti 3+ concentration on the PLZT surface. This higher Ti 3+ surface concentration is responsible for the higher relative dielectric constant measured for the PLZT bulk ceramics.

Microstructure of organometallic derived PLZT ceramics

The PLZT powders with the formula Pb 0.905 La 0.095 (Zr 0.65 Ti 0.35 ) 0.976 O 3 + 3.5 wt.% PhO were prepared by the organometallic precursor method (Pechini and partial oxalate processes). The microstructure of sintered 9.5/65/35 PLZT ceramics obtained from a partial oxalate procedure shows that the outstanding feature of this microstructure is its fairly uniform grains of about 1.8 μm. The microstructure of sintered PLZT ceramics obtained by the Pechini process consists of uniform small randomly-oriented grains tightly bonded together in the central part of the sample with a grain size of about 1.2 μm. Cubic and elongated grains are formed at the sample's border. The microstructures of hot pressed PLZT ceramics obtained from both processes are dense and rather uniform. After a double stage of hot pressing (2 plus 20 h) the microstructure of PLZT is fully dense uniform and homogeneous with a grain size of approximately 2.5 μm.

ＭＡの応用 ＰＬＺＴ圧電セラミック粉末のメカノケミカル合成

The mechanochemical (MC) synthesis of La-modified lead zirconate titanate (PLZT) powder from the constituent oxides was conducted using a planetary ball milling. A single-phase perovskite PLZT powder was synthesized by dry-milling of the oxide mixture for a relatively short period (36ks at a rotational speed of 400r.p.m.). Dense PLZT bulk samples with fine-grained microstructures were obtained even from powders subjected to MC for a short time (3.6ks), at lower sintering temperature than the powders prepared by the conventional wet-mixing process. The present study suggests that the mechanochemical synthesis of PLZT consists of the following three stages: First, the pulverization, intimate mixing and granulation of the starting powders occur at the early stage. Secondly, the crystallites of the powders were increasingly disordered due to the impact of the milling balls. Finally, the reaction between PbO and TiO2 was activated to produce PbTiO3, and (Pb, La) (Zr, Ti)O3 solid solutions were formed by the reaction between PbTiO3 and the remaining oxides.

Synthesis and characterization of 9.5/65/35 PLZT prepared from the polymeric precursors

The 9.5/65/35 PLZT was prepared from the polymeric precursors (the Pechini and partial oxalate process) and by sintering in two stages in an oxygen atmosphere. After thermal treatment at 400°C, the powders were calcinated and sintered at 1200°C with slow heating and cooling rates. The second stage of sintering consisted of hot pressing at the same temperature in oxygen atmosphere. After calcination of PLZT powders obtained by both methods, as well as after sintering of PLZT obtained by Pechini process, the paraelectric cubic phase was formed. After sintering of PLZT obtained by partial oxalate procedure, small tetragonality of crystal structure was observed. After hot pressing PLZT was pseudocubic. SEM microstructural analyses were carried out of the sintering and hot pressed samples and indicated the small grain size less than 2 μm.

Chemical solution technique to prepare perovskite PZT and PLZT thin films and powders

PbZr0.65Ti0.35O3 and Pb0.91La0.09Zr0.65Ti0.35O3 thin films with thickness of around 100 nm were prepared by the chemical solution deposition technique on Si (100) substrate. Complex metal alkoxide precursors were synthesized by alcoholisis and alcohol exchange reactions starting from metallorganics compounds. NMR spectroscopic techniques, 1H and 13C, and FTIR analysis were used to study the arrangement of the metals and oxygen in the precursor molecules. The films were deposited on Si (100) by spin coating technique and thermal treated by Rapid Thermal Processing for film crystallization. The thermal evolution and structural characterization were performed by DTA-TG/FTIR and by glazing incidence XRD and XRD powder. A PLZT powder with a well-crystallized perovskite structure was obtained at 700°C free of pyrochlore phase whereas the PLZT film exhibits a distorted perovskite structure and residual pyrochlore. The PZT films were less crystallized. The silicon substrate affects the crystal structure of the film. The residual acetylacetonate groups in the precursor of PLZT, would reduce the clustering of Zirconium species.

Mechanism of PZT crystallisation under hydrothermal conditionsDevelopment of a new synthesis route

On the basis of a 1-stage hydrothermal process, we first investigated the reaction mechanism responsible for the PZT precipitation. In a first sequence, lead diffuses into the amorphous coprecipitate. By increasing the reaction temperature, these particles dissolve, leading to nucleation and growth of PZT well faceted particles. In a second step, we demonstrated that starting from very fine oxide precursors, a homogeneous PZT solid solution could be formed. Under the same conditions but without any lead precursor, a mixture of KTO (a potassium titanium oxide phase) and tetragonal zirconia is formed. A 2-stage process was developed on these assumptions. The first stage consists in producing the KTO–ZrO 2(T) mixture. In the second stage, this mixture is hydrothermally treated in presence of lead precursor. Pure and homogeneous PZT and PLZT powders were obtained throughout this new synthesis route.

PLZT ceramics prepared from conventional and microwave hydrothermal powders

Phase pure PLZT (3/52/48) powders were synthesized at a low temperature of 138°C by both conventional and microwave hydrothermal (MH) methods without using excess lead content. PLZT ceramics fabricated from the above powders resulted in 96% of theoretical density upon sintering. Properties such as crystallinity. morphology of the as prepared MH powders and densification and miciostructure of the sintered pellets were studied. These properties of MH samples were compared with the properties of those prepared by conventional hydro-thermal method (CH).

Nanocomposite versus monophasic sol-gel processing of PLZT ceramics

Very fine PLZT powders with particle size of-200 nm were synthesized by a nanocomposite method from relatively inexpensive precursors. Pellets made from these powders were sintered to 96% of theoretical density at 1250°C for 4 hrs. The crystallization, densification and microstructure were studied for nanocomposite PLZT in comparison with sintered compacts made from monophasic processing of the same composition.

酢酸鉛を出発原料に用いたＰＬＺＴ粉末の合成

PLZT powder for ferroelectrics ceramics was prepared by a sol-gel method with lead acetate (Pb(C2H3O2)2). The crystallization of the sample could be controlled through the low heating process. Based on the results of the X-ray diffraction analysis, good crystallized PLZT peaks was observed of the sample heated at 850°C.

Low‐Temperature Preparation of Nanocrystalline Lead Zirconate Titanate and Lead Lanthanum Zirconate Titanate Powders Using Triethanolamine

Nanocrystalline lead zirconate titanate (PZT) powders, with a Zr:Ti ratio of 60:40, have been prepared from a solution of triethanolamine (TEA) and Ti4+, Zr4+, and Pb2+ ions. The metal ions were in solution through complex formation with TEA. The soluble metal‐ion–TEA complex formed the precursor material when it was completely dehydrated. Heat treatment of the precursor at 450°C resulted in single‐phase PZT powders. The precursor and the heat‐treated powders have been characterized by using thermal analysis and X‐ray diffractometry (XRD) studies. The average particle size, as measured from X‐ray line broadening and transmission electron microscopy studies, was ∼20 nm. PZT powders modified with 3 mol% of lanthanum (PLZT) also were prepared through this route and were investigated via XRD studies. The dielectric constants of the PZT and PLZT powders were 12475 and 11262, and their corresponding Curie temperatures were 362° and 315°C, respectively.

Citrate route to the preparation of nanometer size (Pb, La) (Zr, Ti) O3 oxide

Abstract Homogeneous and stoichiometric lanthanum-modified lead zirconium titanate (Pb 0.92 La 0.08 )(Zr 0.65 Ti 0.35 )O 3 (PLZT) particles with a nanometer size of 20–40 nm have been prepared by the citrate route. The solubility isotherms for individual metal-citric acid-H 2 O systems at 25 °C were calculated to predict the optimum pH condition, which was found to be 6.5 for preparing pure and stable citrate complexes. A monophasic PLZT powder consisting of monodispersive and nanometer-sized particles could be obtained by thermal decomposition of the optimally prepared citrate precursor at a considerably low temperature of 800 °C. Details of crystallization process and particle characteristics of the citrate-derived PLZT powder have been described along with the preliminary results on the sinterability.

Synthesis of nanophase PLZT (12/40/60) powder by PVA-solution technique

Abstract The preparation of high purity ultrafine lanthanum modified lead zirconate titanate powder has been explored with polyvinyl alcohol. The precursor and calcined powders were examined by thermal analyzer, powder X-ray diffractometer and infrared spectrophotometer. The morphology and homogeneity of the calcined powders were investigated by transmission electron microscope and energy dispersive X-ray spectroscopic studies. The precursor powder transformed into single phase PLZT after calcination for 1 h at 600 °C having the crystallite size of 10 nm.

Synthesis and sintering of PLZT powder made by freeze/alcohol drying or gelation of citrate solutions

Citrate salts of PLZT 9/65/35 were prepared by drying (alcohol and/or freeze drying) and gelation of citrate solutions of PLZT. The decomposition of the citrate salts to form PLZT powder was studied by thermal analysis, X-ray diffraction, and scanning electron microscopy (SEM). It was found that the citrate salts of PLZT composition decompose in two separate stages; after decomposition, powder derived from alcohol dehydration, freeze drying and gelation have similar characteristics. Calcined powders in all cases consisted of 1 μm agglomerates with a surface area of approximately 11 m 2/g. Freeze drying and gelation are preferred over expensive alcohol dehydration. Dense pellets can be obtained from the citrate derived powder by a two stage pressureless sintering process.

Structural analysis of PLZT powders prepared by conventional and precipitation methods

Structural evolution of PLZT 9/65/35 was followed from the full crystallization temperature up to 1200°C. A well developed PLZT structure can be formed in coprecipitated powders after calcination at 550°C for one hour, while oxides mixing required a calcination at 850°C for three hours. Monophasic powders with pseudocubic symmetry were obtained only after calcination at 1200°C.

X-ray, thermal and dielectric studies of chemically derived lanthanum-modified lead zirconium titanate (7:65:35) ceramics

Lanthanum-modified lead zirconium titanate (PLZT) ceramics, a solid solution of PbTiO3 (ferroelectric) and PbZrO3 (anti-ferroelectrics), are considered to be attractive materials for many device applications such as non-volatile memories, transducers and photographic pick-ups. The formation of PLZT solid solution depends to a large extent on the physicochemical characteristics of the starting raw materials [1]. It is well known [2] that the conventional (high-temperature solid-state reaction) method of preparing PLZT powders causes compositional fluctuations and chemical inhomogeneity, which impair the electromechanical properties of the finished products. The powders prepared by chemical methods such as coprecipitation [3], spray drying [4], freeze drying and liquid drying [5] and sol-gel [6] methods have gained tremendous importance because of their better purity, better homogeneity and enhanced reactivity leading to the development of improved ceramics. A recent observations of diffuse phase transition [7] and relaxor behaviour [8, 9] in PLZT have attracted more attention for thorough studies of the compounds (with different La compositions) synthesised from different methods. In this work, PLZT (7:65:35 La:Zr:Ti) powders were prepared by the chemical method of evaporative decomposition of nitrate solutions. Detailed studies on the structure IX-ray diffraction (XRD)] and phase transition (by thermal and dielectric methods) of the fabricated samples were made to obtain a better understanding of this material for device applications. Reagent grade nitrate salts of lead,_ lanthanum and zirconium and metal-alkoxide (tetra-isopropyl titanate) were used to prepare an aqueous solution of the PLZT compound of composition 7:65:35. Lead nitrate, lanthanum nitrate and zirconyl nitrate were first dissolved in doubly distilled water. Tetraisopropyl titanate (a liquid) was then added directly to the nitrate solution while stirring. The titanium hydrolysed to a intermediate Ti(OH)4 phase and slowly redissolved. Concentrated nitric acid (HNOfl was then added to the solution, which increased the rate at which the solution cleared. Caution was exercised in adding HNO3 to prevent a strong exothermic reaction. PLZT powder was then obtained by heating the solution at 230 °C. The dried powder was subsequently calcined at various temperatures ranging from 230 to 920 °C for 16 h in an air atmosphere. The calcined and milled powder was uniaxially cold pressed at 6 x 107 kgm -2 into pellets of diameter 11.2 mm and thickness 1-2 mm using

Synthesis and characterization of PLZT (10/65/35)

Lead zirconate titanate (PZT) powder of composition Pb(Zr0.65Ti0.35)O3 was modified by incorporation of 10% lanthanum as a supervalent cation by the process of evaporative decomposition of aqueous solutions of lead nitrate, lanthanum nitrate, zirconyl nitrate and tetra-isopropyl titanate. X-ray diffraction patterns and infrared spectra of the compound calcined at different temperatures indicate that formation of rhombohedral PLZT is possible at 550°C for 1 H. The room-temperature dielectric constant measured at 1 kHz was found to be 991. From the study of dielectric constant as a function of temperature,Tc was found to be at 85°C. SEM study of the compound has shown grain-size homogeneity and quality of the compound. All these results suggest that this PLZT powder may be suitable for device applications.