PbO Atmosphere Research Articles

Specific features and properties of lead-titanate-based anisotropic ceramics

This work has been devoted to certain microstructure peculiarities of anisotropic materials of the form (Pb,Ca)TiO3 - Σ2i=1 PbB'1-αB''αO3, where B' is W, and B'' is Mg, Zn or Co, Zn. To decrease contamination of the equipment and surroundings the traditional source of a PbO atmosphere (PbO-contained powder) has not been used when the sintering of the ceramics was carried out. In the ceramics under study, a second phase was detected based on titanium oxide whose content and elemental composition have been estimated. The influence of this phase has been studied on structural and electrophysical parameters of relevant materials as their sintering temperature is changed from 1140°C to 1210°C. The increasing content of the second phase in the ceramics diminishes the susceptibility of the material to domain switching resulting in the worsening of electrophysical parameters.

Epitaxial growth of Pb(Zr, Ti)O3thin films on sapphire (0112)

Abstract The structure of Pb(Zr, Ti)O3 films grown on u-Al2O3 (0112) substrates by the RF-sputtering and annealed in the PbO atmosphere has been studied by X-ray diffraction and TEM methods. The Pb(Zr, Ti)O3 phase has been found to be of the perovskite type structure. The films had the strongly pronounced texture formed by large grains with the (110) axis oriented nearly normal to the substrates. The values of the grain size and the grain misorientations have been obtained by TEM. TEM microdiffraction analysis showed the growth of Pb(Zr, Ti)O, grains to be the epitaxial one.

Influence of a PbO compensation atmosphere and surface layers on the electrical properties of (Pb, Nb)-doped TiO 2 varistors

The electrical properties of (Pb, Nb)-doped TiO 2 varistors sintered with and without a PbO compensation atmosphere were investigated. The sample sintered with a compensation atmosphere exhibited higher resistivity as well as lower dielectric constant and dissipation factor. Besides, samples sintered under a PbO atmosphere possess higher I- V nonlinear exponents. By removing the surface layers of samples, the varistor properties were found improved and the effect of compensation via the atmosphere became less significant.

Properties of Electrooptic (Pb, La)(Zr, Ti)O3 Ceramics Fabricated by Partial Coprecipitation Method

Electrooptic ceramics of (Pb, La)(Zr, Ti)O3 were fabricated by a combination of the partial-coprecipitation and doctor-blade methods. The PLZT powder, with particles of submicron size that were excellently dispersed, was prepared by (Zr, Ti)O2 solid-solution powder and PbO and La2O3 oxide powders. The large-scale PLZT ceramics with the dimension of 10×10∼20 cm and thickness of 1.5 mm were molded by the doctor-blade method and then conventionally sintered at 1200∼1250°C for 20∼60 h under the controlled condition of PbO and oxygen atmosphere. The fabricated PLZT ceramics with 0.5 mm thickness showed the transmittance of 65∼67% in the range of wavelength greater than 600 nm, and the quadratic electrooptical coefficient of 4.5×10-16 O2/V2.

Sol-Gel Derived PZT Fibers

ABSTRACTSol-gel routes were developed to prepare densified PZT fibers. The effects of the degree of hydrolysis and the addition of an organic polymer to the precursor sol on fiber forming ability were investigated. Results on the crystalline and microstructural development of gels and fibers are presented. The effects of the incorporation of excess PbO and sintering atmosphere are also discussed, particularly in relation to densification.

Low-temperature synthesis of lead zirconate

In the preparation of piezoelectric and electro-optic ceramics of the lead zirconate (PbZrO3; PZ) family, including lead lanthanum zirconotitanate (PLZT), one is bogged down by difficulties in reproducibly when making ceramic bodies to rigid specifications. For instance, in the case of PZ, in addition to the sensitivity of properties of the ceramic to the sintering conditions and microstructure of the starting powders, there is also the serious problem of PbO melting and evaporation at 880 °C while the final sintering temperature in the conventional mixed oxide process is 1200 °C. Maintaining a PbO atmosphere in the furnace has became a convention to compensate for the loss of PbO, which obviously cannot impart perfect homogeneity and uniform microstructure to the final products. Lead deficiency is also a problem with PbTiO3 [1]. Recently [2] BaTiO3 (BT) and mixed perovskites have been prepared by the sol-gel route at just 88 °C, yielding a particle size of 0.05-0.1 m. Similarly, it is highly desirable to bring down the reaction temperature for PZ systems to below the PbO melting point (s80 oc). In this letter we report our experiments to achieve the objective of lowering the PZ reaction temperature. The reaction performed may be described as a self-propagating combustion reaction [3] which decomposes the nitrate precursors into an intimate mixture of the component oxides. The required amounts of all nitrates, Pb(NO3)2, ZrO(NO3)2.xHpO, Ba(NO3)2 and TIC14 to make PZ and BT were dissolved in distilled water to which an appropriate amount of (1:1.2 to 1:2 by weight) citric acid (C6HsO7.H20) was added to give a white-coloured thick solution. This solution was neutralized with ammonia solvent until we obtained a clear, transparent solution which was boiled slowly over a hotplate (about 300 °C) and, finally, we were left with a lightweight black powder which was the precursor. Upon further heating the black powder caught fire, giving a yellow-coloured (for BT white-coloured) powder within 5 min. Pellets of this yellow powder were sintered in air for 3 h at 400 °C, 1 h at 600 °C and 700 °C to give the final samples. Samples thus prepared were studied using X-ray powder diffraction (XRD), differential scanning calorimetry (DSC; Dupont-9900) and scanning electron microscopy (SEM; Jeol-JSM35). A laboratory-made, calibrated (with Li2SO4.HpO ) differential thermal analysis (DTA) set-up was used to monitor the reaction

Growth of superconducting Bi-Pb-Sr-Ca-Cu-O films by an ultrasonic spray pyrolysis method

Superconducting films of Bi-Pb-Sr-Ca-Cu-O on MgO (1 0 0) substrate were prepared by an ultrasonic spray pyrolysis method. The substrate was rotated during a deposition process to increase uniformity on the film surface. The films were sintered both in air and PbO atmosphere. Highly c-axis oriented films which have a low T c phase ( T c = 80 K) in the bismuth superconductor can be reproducibly generated. X-ray diffraction data for the low T c phase was indexed to (0 0 l) reflections of the Bi 2Sr 2CaCu 2O 8 structure. The c-axis lattice parameter estimated from the diffraction angles was 30.90 Å. Films annealed in PbO atmosphere produced a high T c phase ( T c = 110 K) in the bismuth superconductor.

プラズマ制御型スパッタ法によるセラミックス多積層膜の作製と界面の構造

For artificial construction of new high Tc superconducting structures, the preparation of compositionally modulated films has been studied by using such processes as the laser ablation 1), multi-targets sputtering 2), and plasma-controlled sputtering 3). Here, we report on the syntheses of Bi-Sr-Ca-Cu-O and Y-Ba-Cu-O multilayered films by plasma controlled sputtering.The apparatus used for the film preparation has two solenoid coils which can work for varying the shape of the plasma above the targets. The sputtered area can be controlled by changing the coil current. Binary targets consisting of a smaller Ca1Cu1.5Ox(φ40mm) and a larger Bi1.6Sr1Oy(φ70mm) disks were used for the preparation of Bi-Sr-Ca-Cu-O modulated film. In case of the synthesis of Y-Ba-Cu-O modulated film, a smaller Y1Cu1.25Ox(φ50mm) and a larger Ba1Cu1Oy(φ70mm) disks were employed. The substrates, MgO(100), were. eated from 450°C to 550°C.In case of the preparation of compositionally modulated Bi-Sr-Ca-Cu-O film, the periodicity of 20A was designed in view of c-axis length of 18A between two Bi2O2 layers in the Bi2Sr2Ca2Cu3Ox structure. By the low angle X-ray diffraction, peaks attributed to planar spacing of 19.9A appeared. Annealing the as-grown amorphous film in a PbO atmosphere made it superconductor whose Tconset of 113K and Tczero of 103K. Auger electron spectroscopy revealed the existence of Pb in the film.X-ray diffraction patterns of Y2Cu2O5 and BaCuO2 were observed for the films prepared from Y-Cu-O and Ba-Cu-O targets, respectively. When we designed the multilayered film with periodicity of 12A, peaks identified to (003) and (006) planes of Ba2YCu3O7-δ were observed for the as-grown film prepared at the substrate temperature of 500°C. Increase of substrate temperature up to 550°C made their intensities high. The as-grown film deposited at the substrate temperature of 450°C was annealed to be strongly c-axis oriented Ba2YCu3O7-δfilm. Planar-like crystals texture was observed in the annealed film by SEM measurement. Its Tconset and Tczero were 65K and 49K, respectively.

Anomaly of dielectric properties in tens-nanometer-thick lead lanthanum zirconate titanate films on a platinum substrate

Transparent ultrathin films (<100 nm) of lead lanthanum zirconate titanate (PLZT) with good dielectric properties were successfully grown on a platinum plate by rf magnetron sputtering and following an anneal in PbO atmosphere. The sputtering conditions were controlled by monitoring the plasma emission from the sputtering species. The PLZT thin films were deposited at an extremely low growth rate of 36 nm/h at 400 °C and annealed at 800 °C for 3 h in PbO atmosphere. The obtained thin films are oriented to [110] of the perovskite-type structure and have relatively low dc conductivity (∼10−7 Ω−1 cm−1). The evaluated dielectric constants are anomalously large around 5000 at room temperature and 1 kHz.

Annealing in a PbO atmosphere for high T c superconductivity of Bi-Sr-Ca-Cu-O films

(Bi-Sr-O)/(Ca-Cu-O) multilayered films were prepared by a plasma-controlled sputtering method and annealed under various conditions to induce the superconductivity in the films. The annealing in the presence of PbO vapor at 860 °C was effective to convert the unleaded insulating multilayered films to superconductors with onset and zero-resistivity temperatures of 113 and 103 K, respectively. Auger electron spectroscopy verified the incorporation of Pb in the films.

Magnetic properties of BiFeO3-BaTiO3 and BiFeO3-PbTi(Zr)O3 glassy sputtered films

Magnetic properties of glassy oxide films which exhibit ferromagnetism and ferroelectricity simultaneously above room temperature prepared by reactive rf sputtering are presented. Nominal film composition is the solid solution compound system expressed by (1−x)BiFeO3-x ABO3, x=0–1 where ABO3 denotes ferro- (antiferro-) electric perovskites, such as BaTiO3, PbTiO3, and PbZrO3. Spontaneous magnetization 4πMs for as-deposited films is small behaving paramagnetically and does not show the compositional dependence. After annealing at temperatures of 600–700 °C in either air or PbO atmosphere, considerably large 4πMs exceeding 1 kG appears at the solid solution composition. All samples with large 4πMs are x-ray amorphous and a rapid decrease in 4πMs takes place after annealing at higher temperatures (≳800 °C), where still unidentified crystallites are precipitated. Mössbauer absorption spectra were done to understand the origin of ferromagnetism. Besides pronounced magnetic (and/or dielectric) properties, these films have a high transmittance from visible through near-infrared regions, so that they are expected to be useful as optoelectronic device materials.

Sintering of PZT Ceramics: I, Atmosphere Control

Methods of PbO atmosphere control during the sintering of PZT ceramics are briefly reviewed. The problem of atmosphere control of PZT compositions containing a PbO excess (PbO/(Zr,Ti)O2>1) is discussed. Weight-loss experiments were performed to compare with behavior predicted by reference to the PbO-rich part of the ternary PbO-ZrO2-TiO2 phase diagram. The results indicated that the PbO activity of a PZT composition is a function of the excess PbO content, contrary to earlier reports. Experimental procedures were established in order to control the PbO content within satisfactory limits. The effects of various packing powders on the PbO content of sintered PZT compacts were evaluated.

ChemInform Abstract: LOW‐TEMPERATURE DENSIFICATION OF LEAD ZIRCONATE TITANATE WITH VANADIUM PENTOXIDE ADDITIVE

AbstractZusätze von 0.1‐6.0 Gew.‐% V2O5 beschleunigen die Verdichtung von Pb(Zr0.53Ti0.47)O3 unterhalb 975 °C und ersparen dadurch eine Kontrolle der PbO‐Aktivität in der Sinteratmosphäre.

Low‐Temperature Densification of Lead Zirconate‐Titanate with Vanadium Pentoxide Additive

Additions of 0.1 to 6.0 wt% V2O, to lead zirconate titanate (PZT) ceramics promoted rapid densification below 975°C, thereby eliminating the need for PbO atmosphere control The base PZT, Pb(Zr0.53Ti0.47)O3, was prepared by coprecipitation from mixed oxides and butoxides. The V2O5 was incorporated as a batch addition during the PZT coprecipitation process, as mill additions to the calcined precipitated powder, and to a commercial PZT powder. Densification rates were enhanced by the addition of V2O5 (>98% of theoretical density was obtained in ∼15 min at 960°C by the addition of 0.1 to 1.0 wt% V2O5, compared to 4 h at 1280°C for the base PZT). Dielectric properties and piezoelectric coefficients varied slightly within the optimum range of 0.25 to 1.0 wt% V2O5 addition but were at least comparable to the base PZT. Indications are that V2O5 becomes incorporated into the surface layers of the oxide powders during mixing (or in the coprecipitation process) and that the accelerated densification is due to enhanced surface activation and liquid‐phase sintering.

Solubility Limit of La in the Lead Zirconate‐Titanate System

The disappearing‐phase method was used to determine the extent of the solid‐solution region of the PLZT system for conventionally sintered ceramics prepared at 1100° and 1300°C in a PbO atmosphere provided by pbZrO3. A decrease in the firing temperature from 1300° to 1100°C lowers the solubility limit by 5 to 8 at.% La. Beyond the limits of solubility, additional La forms La2Zr2O7 and/or La2Ti2O7. The limit determined by the disappearing‐phase method (1300°C firing) is compared to values determined by the parametric method. The Curie temperature is stabilized at 5 at.% La for modified PbZrO3 (1300°C firing).

Substitution of Bi and Nb Ions in Lead Zirconate-Titanate

Solid-state substitution of Bi and Nb ions in the perovskite crystal structure of Pb(Ti0.47Zr0.53)O3 was investigated by sample weight changes at 1150°C in an “equilibrium” PbO atmosphere. A model is discussed that includes the effect of charge neutralization, requiring weight losses for A-site substitutions and weight gains for B-site substitutions. Experiments support the substitution of Bi as Bi3+ on the Pb2+ A site and Nb as Nb5+ on the (Ti,Zr)4+ B site of lead zirconate-titanate. For each mole of BiO1.5 added to a specimen, 1.5 moles of PbO are lost; for each mole of NbO2.5 added, 0.5 moles of PbO are gained. These results agree with the proposed model and with ionic size arguments. The weight changes were time-dependent during the first 30 to 40 h at 1150°C. This behavior is accounted for by the presence of transient second phases.

Anomalous Expansion in the Firing Process of Piezoelectric Ceramics Containing PbO

Experimental studies were made on the firing process of the piezoelectric ceramics containg PbO such as PbZrO3, PbTiO3, Pb(Zr-Ti)O3, Pb(Ta0.5-Fe0.5)O3 and so on. The results obtained are summarized as follows.1) When the powder mix of PbO⋅ZrO2 was heated at the constant rate of 300°C/hr in air, PbZrO3 was formed from the temperature about 600°C and the solid reaction was finished at the temperature of maximum expansion of about 1100°C. For specimens fired at the temperature above 1200°C, the pattern of ZrO2 was observed by X-ray diffraction and the ceramic density was decreased as compared with that fired at the lower temperature. This means that at this temperature PbZrO3 decomposes by the evaporation of PbO.2) When the powder mix of PbO⋅TiO2 was heated, PbTiO3 was formed from the temperature about 500°C and the solid reaction was finished at about 800°C.3) In the case of the raw mix of Pb(Zr-Ti)O3 ceramics, maximum expansion in the firing process was observed at 500°-600°C. The shrinkage curve fired in PbO atmosphere was considerably different from that fired in air.4) In the firing process of the ferroelectric Pb(Ta0.5-Fe0.5)O3 ceramics from the raw mix of 4PbO+Ta2O5+Fe2O3, remarkably anomalous expansion was observed at 600°-900°C with the maximum linear expansion of 22%. This fact is very interesting in connection with the solid reaction.