Effects of milling time and calcination condition on phase formation and particle size of lead zirconate nanopowders prepared by vibro-milling

Effect of calcination conditions on phase formation and particle size of lead zirconate (PbZrO₃) powders synthesized by a solid-state reaction with different vibro-milling times was investigated. A combination of the milling time and calcination conditions was found to have a pronounced effect on both the phase formation and particle size of the calcined PbZrO₃ powders. The calcination temperature for the formation of single-phase perovskite lead zirconate was lower when longer milling times were applied. The optimal combination of the milling time and calcination condition for the production of the smallest nanosized (∼28 nm) high purity PbZrO₃ powders is 35 h and 750 °C for 4 h with heating/cooling rates of 30 °C/min, respectively.     

Effect of calcination condition on phase formation and particle size of lead titanate powders synthesized by the solid-state reaction

A perovskite-like phase of lead titanate, PbTiO₃, has been synthesized by a solid-state reaction via a rapid vibro-milling technique. Phase formation of the calcined powders has been investigated as a function of calcination temperature, soaking time and heating/cooling rates by DTA and X-ray diffraction (XRD) techniques. Moreover, morphology and particle size evolution have been determined via SEM technique, respectively. It has been found that single-phase PbTiO₃ powders were successfully obtained for calcination conditions of 550 °C for 4 h or 600 °C for 1 h with heating/cooling rates of 20 °C/min. Higher temperatures clearly favoured particle growth and the formation of large and hard agglomerates.     

Effects of calcination conditions on phase and morphology evolution of lead zirconate powders synthesized by solid-state reaction

Lead zirconate (PbZrO₃) powder has been synthesized by a solid-state reaction via a rapid vibro-milling technique. The effects of calcination temperature, dwell time and heating/cooling rates on phase formation, morphology, particle size and chemical composition of the powders have been investigated by TG-DTA, XRD, SEM and EDX techniques. The results indicated that at calcination temperature lower than 800 °C minor phases of unreacted PbO and ZrO₂ were found to form together with the perovskite PbZrO₃ phase. However, single-phase PbZrO₃ powders were successfully obtained at calcination conditions of 800 °C for 3 h or 850 °C for 1 h, with heating/cooling rates of 20 °C/min. Higher temperatures and longer dwell times clearly favored the particle growth and formation of large and hard agglomerates.     

Effect of vibro-milling time on phase formation and particle size of lead zirconate nanopowders

A perovskite phase of lead zirconate, PbZrO₃, nanopowder was synthesized by a solid-state reaction via a rapid vibro-milling technique. The effect of milling time on the phase formation and particle size of PbZrO₃ powder was investigated. Powder samples were characterized using TG-DTA, XRD, SEM and laser diffraction techniques. It was found that an average particle size of 50 nm was achieved at 25 h of vibro-milling after which a higher degree of particle agglomeration was observed upon continuation of milling to 35 h. In addition, by employing an appropriate choice of milling time, a narrow particle size distribution curve was also observed.     

Preparation and characterisation of ultrafine lead titanate (PbTiO3) powders

Ultrafine lead titanate (PbTiO₃) powders in tetragonal form have been successfully prepared via three processing routes, namely, conventional co-precipitation, microemulsion-refined freeze drying, and microemulsion-refined co-precipitation. The formation process of lead titanate from the resulting precursors was monitored using techniques such as thermal analyses and X-ray diffraction for phase identification. It was found that the two microemulsion-refined processing routes led to a lower formation temperature for lead titanate than that observed in the conventional co-precipitation route. The three lead titanate powders have also been compared for particle and agglomerate size distributions and specific surface area. It appears that the microemulsion-refined co-precipitation is the technique which results in the formation of the finest lead titanate powder amongst the three processing routes investigated in the present work. This revised version was published online in September 2006 with corrections to the Cover Date.     

Effect of excess Pb on formation of perovskite-type 0.67Pb(Mg<Subscript>1/3</Subscript>Nb<Subscript>2/3</Subscript>)O<Subscript>3</Subscript>-0.33PbTiO<Subscript>3</Subscript> powders synthesized through a sol–gel process

Perovskite-type 0.67Pb(Mg_1/3Nb_2/3)O₃-0.33PbTiO₃ (PMNT) powders were fabricated by using a sol–gel process. Excess Pb(CH₃COO)₂·3H₂O (0, 2, 5, 10 or 15 mol%) was added to starting materials to compensate PbO loss from volatilization during heat treatment. X-ray diffraction (XRD) was employed to investigate the effect of excess Pb on the perovksite phase formation of the PMNT powders. It was found that the optimal level of the excess Pb content is 5 mol%. When the raw materials contained 5 mol% excess Pb, the PMNT powders of purest perovskite form was obtained at the calcination temperature of 850 °C. In the PMNT powders, most part of the intermediate phase was Pb-rich pyrochlore Pb₂Nb₂O₇ which was transformed into perovskite phase after calcination at 650 °C, while the residual pyrochlore phase was Pb-deficient Pb₃Nb₄O₁₃ which required calcination at a higher temperature (650–850 °C) to transform into perovskite phase. Compared with the conventional solid-state reaction methods and the solution-based methods reported previously, the present sol–gel route is better at synthesizing PMNT powders of perovskite phase at a low temperature.     

Preparation of lead titanate ultrafine powders from combined polymerisation and pyrolysis route

Lead titanate (PbTiO₃) nanopowders were prepared from a monomeric metallo-organic precursor through combined solid-state polymerisation and pyrolysis (CPP). This makes it possible to adjust the mean particle size in a wide range by just choosing the appropriate reaction temperature. This particular preparation route was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The size effects in the resulting PbTiO₃ nanopowders were investigated by standard methods such as X-ray diffraction (XRD) and FT-Raman spectroscopy. By using the double Voigt method in analysing the XRD results, smaller mean particle size and narrower size distributions were found for powders prepared at lower reaction temperatures, with the tetragonality being reduced. Preliminary electron paramagnetic resonance (EPR) measurements demonstrate that paramagnetic chromium probe ions incorporate very well into the PbTiO₃ lattice, particularly enabling corresponding high-field EPR measurements which have proven exceedingly informative in our previous investigations on Mn²⁺-doped barium titanate (BaTiO₃) nanopowders. Moreover, the potential of the CPP route is enhanced to prepare perovskitic stoichiometric solutions for advanced practical applications.     

Influence of calcination conditions on phase formation and particle size of indium niobate powders synthesized by the solid-state reaction

A wolframite-type phase of indium niobate, InNbO₄, has been synthesized by a solid-state reaction via a rapid vibro-milling technique. The formation of the InNbO₄ phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques. Single-phase InNbO₄ powders have been obtained successfully for calcination condition of 900 °C for 4 h or 950 °C for 2 h with heating/cooling rates of 30 °C/min. Higher temperatures and longer dwell times clearly favoured particle growth and the formation of large and hard agglomerates.     

A modified two-stage mixed oxide synthetic route to lead zirconate titanate powders

An approach to synthesis lead zirconate titanate [Pb(Zr_1−xTi_x)O₃; PZT] powders with a modified two-stage mixed oxide synthetic route has been developed. To ensure a single-phase perovskite formation, an intermediate phase of zirconium titanate (ZrTiO₄) was employed as starting precursor. The formation of perovskite phase in the calcined PZT powder has been investigated as a function of calcination temperature, soaking time and heating/cooling rates by differential thermal analysis (DTA) and X-ray diffraction (XRD) techniques. The morphology evolution was determined by scanning electron microscopy (SEM) technique. It has been found that the unreacted PbO and ZrTiO₄ phases tend to form together with PZT, with the latter appearing in both tetragonal and rhombohedral phases, depending on calcination conditions. It is seen that optimisation of calcination conditions can lead to a 100% yield of PZT in a tetragonal phase.     

Effects of calcination conditions on phase formation and particle size of indium niobate nanopowders synthesized by the solid-state reaction

A wolframite-type phase of indium niobate, InNbO₄, has been synthesized by a solid-state reaction via a rapid vibro-milling technique. The formation of the InNbO₄ phase in the calcined powders has been investigated as a function of calcination conditions by TG–DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques. It has been found that single-phase InNbO₄ powders have been obtained successfully at the calcination condition of 950 °C for 2 h with heating/cooling rates of 30 °C/min. Higher temperatures and longer dwell times clearly favoured particle growth and the formation of large and hard agglomerates.     

Ceramic/natural rubber composites: influence types of rubber and ceramic materials on curing,mechanical, morphological,and dielectric properties

Influence of different types of rubber and ceramic material on cure characteristics, mechanical, morphological, and dielectric properties of natural rubber (NR) vulcanizate was studied. Two types of ferroelectric ceramic materials: barium titanate (BaTiO₃) and lead titanate (PbTiO₃) were prepared by solid-state reaction with calcinations at 1100 °C for 2 h. The ceramic powders were then characterized by X-ray diffraction (XRD), particle size analyzer, and SEM techniques. Ceramic/rubber composites were then prepared by melt mixing of rubber and ceramic powders. Two different types of NR (i.e., epoxidized NR [ENR] and unmodified NR) and two types of ceramic powders (i.e., BaTiO₃ and PbTiO₃) were exploited. It was found that incorporation of ceramic powders in rubber matrix and the presence of epoxirane rings in ENR molecules caused faster curing reaction, and higher delta torque but lower elongation at break. This is attributed to lower mobility of molecular chains and higher interaction between ENR molecules. Furthermore, SEM results revealed that the BaTiO₃ composites showed finer and better distribution of the particles in the rubber matrix than that of the PbTiO₃ composite. This caused superior mechanical properties of the BaTiO₃ composites. Furthermore, higher dielectric constant and loss tangent was observed in the ENR/BaTiO₃ composites.     

Mechanochemical effects on the properties of starting mixtures for PbTiO3 ceramics by using a novel grinding equipment

The effects of milling were studied using a newly developed multi-ring media-type grinding machine on the synthesis processes of PbTiO₃ ceramics from PbO-TiO₂ mixed sols. The temperature of the endothermic and exothermic DTA peaks, corresponding to dehydration and crystallization, decreased with milling time. After milling the mixed sol for 5 min and heating to 823 K, the product was a single-phase PbTiO₃. This suggests rapid homogenization and formation of lead titanate precursors during milling. The effects of milling were revealed to be much less when mixtures of dry and wet powders were used.     

Effects of milling method and calcination condition on phase and morphology characteristics of Mg4Nb2O9 powders

Magnesium niobate, Mg₄Nb₂O₉, powders has been synthesized by a solid-state reaction. Both conventional ball- and rapid vibro-milling have been investigated as milling methods, with the formation of the Mg₄Nb₂O₉ phase investigated as a function of calcination conditions by DTA and XRD. The particle size distribution of the calcined powders was determined by laser diffraction technique, while morphology, crystal structure and phase composition were determined via a combination of SEM, TEM and EDX techniques. The type of milling method together with the designed calcination condition was found to show a considerable effect on the phase and morphology evolution of the calcined Mg₄Nb₂O₉ powders. It is seen that optimization of calcination conditions can lead to a single-phase Mg₄Nb₂O₉ in both milling methods. However, the formation temperature and dwell time for single-phase Mg₄Nb₂O₉ powders were lower with the rapid vibro-milling technique.     

Effects of vibro-milling time on phase formation and particle size of Zn3Nb2O8 nanopowders

A monoclinic phase of zinc niobate, Zn₃Nb₂O₈, nanopowder was synthesized by a solid-state reaction via a rapid vibro-milling technique. The effect of milling time on the phase formation and particle size of Zn₃Nb₂O₈ powder was investigated. The formation of the Zn₃Nb₂O₈ phase in the calcined powders has been investigated using DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and laser diffraction techniques. It was found that an average particle size was achieved at 20 h of vibro-milling after which a higher degree of particle agglomeration was observed on continuation of milling to 30 h. In addition, by employing an appropriate choice of the milling time, a narrow particle size distribution curve was also observed.     

Effect of calcination conditions on phase formation and particle size of Zn3Nb2O8 powders synthesized by solid-state reaction

The solid-state mixed oxide method via a rapid vibro-milling technique is explored in the preparation of single-phase Zn₃Nb₂O₈ powders. The formation of the Zn₃Nb₂O₈ phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques. It has been found that the minor phases of unreacted ZnO and Nb₂O₅ precursors and the columbite ZnNb₂O₆ phase tend to form together with the Zn₃Nb₂O₈ phase, depending on calcination conditions. It is seen that optimization of calcination conditions can lead to a single-phase Zn₃Nb₂O₈ in a monoclinic phase.     

Sonocatalyzed hydrothermal preparation of lead titanate nanopowders

Nanoparticles of perovskite lead titanate, PbTiO₃, were successfully prepared in a stoichiometric proportion at conspicuously low temperature and short reaction time of only 130 °C and 3.5 h. The employment of ultrasonic treatment prior to hydrothermal reaction, or so-called “sonocatalyzed hydrothermal reaction”, was examined in detail. Roles of ultrasonic wave both as a catalyst to lower the hydrothermal reaction temperature affording the phase-pure PbTiO₃ and as an external influence to provide better size homogeneity were discussed.     

Study on the synthesis and ion-exchange properties of layered titanate Na2Ti3O7 powders with different sizes

Layered titanate Na₂Ti₃O₇ powders with varying sizes were prepared by solid-state reaction of Na₂CO₃ and TiO₂ with different average particle sizes. The structures of the titanates and the products which had undergone H⁺ and Ag⁺ exchange were investigated by XRD, TEM and BET analysis. The influence of the particle size of starting material TiO₂ on the reaction rate, the particle size and ion-exchange property of the resulting products was studied. It is found that nanometer sized TiO₂ facilitates the solid-state reaction and leads to the formation of ultrafine titanate. The H⁺-exchange property is improved by decreasing the particle size of Na₂Ti₃O₇ and the small sized layered titanate can be exfoliated easily by AgNO₃ solution.     

Effects of intense plastic straining on the structure of barium,lead, and cadmium titanates

Under the action of intense plastic straining (IPS), barium titanate (BaTiO₃) exhibits a phase transition from the tetragonal to cubic structure, while lead titanate (PbTiO₃) shows a tendency to such a transformation. In cadmium titanate (CdTiO₃), the IPS induces a transition from the perovskite to ilmenite phase.     

Effect of calcination conditions on phase formation and particle size of nickel niobate powders synthesized by solid-state reaction

The solid-state mixed oxide method via a rapid vibro-milling technique is explored in the preparation of single-phase nickel niobate (NiNb₂O₆) powders. The formation of the NiNb₂O₆ phase in the calcined powders has been investigated as a function of calcination conditions by TG-DTA and XRD techniques. Morphology, particle size and chemical composition have been determined via a combination of SEM and EDX techniques. It has been found that the minor phases of unreacted NiO and Nb₂O₅ precursors and the Ni₄Nb₂O₉ phase tend to form together with the columbite NiNb₂O₆ phase, depending on calcination conditions. More importantly, it is seen that optimization of calcination conditions can lead to a single-phase NiNb₂O₆ in an orthorhombic phase.     

Phase and morphology evolution of magnesium niobate powders synthesized by solid-state reaction

Magnesium niobate (MgNb₂O₆; MN) powders have been prepared and characterized by TG-DTA, XRD, SEM and EDX techniques. The effect of calcination temperature, dwell time and heating/cooling rates on phase formation, morphology and chemical composition of the powders are examined. The calcination temperature and dwell time have been found to have a pronounced effect on the phase formation of the calcined magnesium niobate powders. It has been found that the minor phases of unreacted MgO and Nb₂O₅ phases tend to form together with the columbite-type MgNb₂O₆ phase, depending on calcination conditions. It is seen that optimisation of calcination conditions can lead to a single-phase MgNb₂O₆ in an orthorhombic phase. Higher calcination times and heating/cooling rates clearly favoured particle growth and the formation of large and hard agglomerates.