A diffusive model of Pb2+ release by lead-ceramic glazes

A diffusive model for the release of Pb²⁺, both from granulates and from glazes deposed on majolica, was obtained by means of electron paramagnetic resonance (EPR) measurements on lead-ceramic glazes doped with CuO, of variable composition due to the substitution of the K⁺ ion with Li⁺, Na⁺, Rb⁺, Tl⁺ or Cs⁺ ions, and through the definition of empirical parameters related to composition and to ionic radii. In the case of majolica-deposed glazes, the different emission values were attributed to ionic migration across the glass-biscuit interface.     

Electrochemical polymerization of benzene in the presence of Ag+, Pb2+ and Cu+ ions

Poly(p-phenylene) (PPP) films were synthesized by using benzene and fluorosulphonic acid (FSO₃H) as a strong acid containing Ag⁺, Pb²⁺ and Cu⁺ ions in methylene chloride (CH₂Cl₂) solution. Addition of Ag⁺ or Pb²⁺ ions into the polymerization medium improved the PPP films formation, but Cu⁺ ion did not have an effect on polymerization. PPP films were characterized by cyclic voltammetry, IR and TGA. Dry conductivities were measured by using four probe technique. Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

Comparative investigation on the effect of alkaline earth oxides on the intensity of absorption bands due to Cu<Superscript>2+</Superscript>, Mn<Superscript>3+</Superscript> and Cr<Superscript>3+</Superscript> ions in ternary silicate glasses

Absorption characteristics of Cu²⁺, Mn³⁺ and Cr³⁺ ions in ternary silicate (20Na₂O·10RO·70SiO₂, where R=Ca, Sr, Ba) glasses were investigated. The intensities of absorption bands due to Cu²⁺ ion was found to increase with increasing ionic radii of the alkaline earth ions whereas it was found to decrease in case of Mn³⁺ and Cr³⁺ ions with increasing ionic radii of the alkaline earth ions. The results were discussed in the light of relation between linear extinction coefficients of these ions and coulombic force of alkaline earth ions. The change in intensities of Cu²⁺, Mn³⁺ and Cr³⁺ ion is attributed due to change in silicate glass compositions.     

Luminescence properties for the high-pressure polymorphs of CaSiO3:Pb2+ and SrSiO3:Pb2+

High-pressure phases of CaSiO₃:Pb²⁺ and SrSiO₃:Pb²⁺ phosphors were synthesized at 40–55 kbar and 1000°C, $\text{viz}$. δ-CaSiO₃:Pb²⁺, δ-SrSiO₃:Pb²⁺, and δ′-SrSiO₃:Pb²⁺, and their luminescence properties were investigated. Among them, δ-CaSiO₃:Pb²⁺ was found to give a strong violet-blue emission ($\text{ca}$. 341 nm) as well as β-CaSiO₃:Pb²⁺ (an atmospheric phase), and the emission intensity of SrSiO₃:Pb²⁺ drastically increased when the host lattice transformed into high-pressure phases (δ and δ′ forms). These results were discussed by considering their structures and quenching temperatures of luminescences.     

Luminescent properties of Pb<Superscript>2+</Superscript>- and Mn<Superscript>2+</Superscript>-activated CdI<Subscript>2</Subscript> crystals

The luminescent properties of CdI₂, CdI₂:Pb²⁺, CdI₂:Mn²⁺, and CdI₂:Pb²⁺,Mn²⁺) crystals have been studied at temperatures from 85 to 295 K under optical and x-ray excitation. Analysis of new and earlier spectroscopic data suggests that the 560-nm luminescence of CdI₂:Pb²⁺ and CdI₂:(Pb²⁺,Mn²⁺) crystals under excitation on the long-wavelength component of the A absorption band of Pb²⁺ centers is due to Pb²⁺-bound anion excitons. The 640-to 660-nm emission of these crystals is attributable to α centers. The manganese luminescence in the codoped material originates from both intracenter Mn²⁺ excitations and a sensitized process due to energy transfer from the host and Pb²⁺-related centers. The mechanisms of recombination and energy transfer processes in cadmium iodide crystals codoped with Pb²⁺ and Mn²⁺ are discussed.     

Electrical Conductivity of Bi<Subscript>2</Subscript>WO<Subscript>6</Subscript> Crystals Doped with Ca<Superscript>2+</Superscript>, Pb<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript>, and Ba<Superscript>2+</Superscript>

Single crystals of Bi₂WO₆ (a layered perovskite-like compound) doped with Ca²⁺, Pb²⁺, Sr²⁺, and Ba²⁺ on the Bi³⁺ site are grown, and their oxygen ionic conductivity is measured along the polar axis. The intrinsic conductivity of the doped crystals differs insignificantly from the conductivity of undoped Bi₂WO₆, indicating that the oxygen ions in the Bi₂O₂ layers contribute little to the oxygen ionic conductivity of the crystals. The sharp change in the activation energy for conduction at 600°C attests to a transition from one conduction mechanism to another in going from low to high temperatures.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 7, 2005, pp. 863–865.Original Russian Text Copyright © 2005 by Kharitonova, Voronkova, Yanovskii.     

Synthesis and photoluminescence of Pb<Superscript>2+</Superscript> doped SrB<Subscript>2</Subscript>O<Subscript>4</Subscript>

Pure and Pb²⁺ doped SrB₂O₄ materials were prepared by a solution combustion synthesis method. The synthesized materials were characterized by using the powder XRD and FTIR. The photoluminescence properties of Pb²⁺ doped SrB₂O₄ materials were investigated using spectrofluorometer at room temperature. The emission and excitation bands of SrB₂O₄: Pb²⁺ was observed at 363 and 270 nm, respectively. The dependence of the emission intensity on the Pb²⁺ concentration for SrB₂O₄: Pb²⁺ was investigated and the critical Pb²⁺ concentration was determined The text was submitted by the authors in English.     

Fabrication of (BiGaPb)2Sr2Ca2Cu3O10+y glass-ceramic superconductor rods

Glass samples with a nominal composition of Bi₁₂Ga_0.4Pb_0.4Sr₂Ca₂Cu₃O_10+y were prepared as rods having a diameter of 13mm and 20cm long by melt casting technique. Sintering process was performed by applying a direct current to the glass rods. Three different current application stages were used and crystallisation of the glass rods were obtained. The XRD studies of the material showed that crystallised grains were preferably c-axis oriented. The best T_c was obtained at 107K and T_zero was obtained at 101K. These results were also confirmed by the D.C. Susceptibility measurements. After the optimum processing condition the maximum transport current density was found to be 9700 A/cm² at 4.2K.     

Electron transfer and intershell spectroscopic parameters of Pb2+: Changes when lead halide films interact with alkali halide substrates

UV spectral data for Pb²⁺ highly diluted in alkali halide crystals and in lead halide thin films are shown to be consistent in the context of current inorganic spectroscopy. For Pb²⁺ in (i) alkali halides and (ii) lead halides the optical electronegativities are 1.2 and 1.4 respectively, while for the ¹S₀→³P₁ frequency (v_s?p) relationship (v_s?p = v_f?v_fmh where h is the nephelauxetic parameter of the complexing halide ion), the values of v_f are 60 700 cm^-1 and 64 400 cm^-1 and the values of m are 0.20 and 0.22 respectively. The results indicate that the modified Pb²⁺ ion model used for Pb²⁺ ions in alkali halide crystals can be extended to Pb²⁺ halide salts. These rationalizations indicate the usefulness of UV spectroscopic measurements for studying the penetration of lead halide thin films into crystalline alkali halides. Spectral changes occuring when sandwiches of lead halide films between NaCl and KBr substrates are maintained at 300°C indicate substantial evaporation of the lead halide film and preference of Pb²⁺ to diffuse into KBr rather than into NaCl.     

Luminescent properties of Cu+/Sn2+-activated aluminophosphate glass

A robust aluminophosphate glass matrix containing substantial amounts of Cu₂O and SnO has been prepared by the melt-quenching technique, and the luminescent properties have been assessed. The as-prepared material exhibits tunable luminescence by variation of excitation wavelength, in connection with the distinct excitation/emission properties of Cu⁺ ions and twofold-coordinated Sn centers in the host. Under excitation of both Cu⁺ and Sn species at 300 nm, the co-doped material exhibits a bright whitish luminescence, whereas excitation at 360 nm produces an intense orange emission arising merely from Cu⁺ ions. Thus, white light generation is deemed realizable by combination of cool-bluish emission intrinsic to Sn centers with the warm-orange emission from Cu⁺ ions. The optical properties of the material after heat treatment have been also investigated. Results indicate the chemical reduction of ionic copper via Sn²⁺ ultimately producing Cu nanoparticles as evidenced by the surface plasmon resonance. Consequently, the excitation-wavelength dependent photoluminescence bands appear suppressed in relation to Cu⁺ basically and show a dip attributed to light reabsorption by the plasmonic Cu particles.     

Synthesis and photochemical properties of Cu2+ doped layered hydrogen titanate

Cu²⁺ doped layered hydrogen titanate was prepared by the calcination of K₂CO₃, TiO₂ and CuO mixtures with the K₂CO₃:TiO₂:CuO molar ratio of 1:2.5(1−x):2.5x at 1200°C for 5 h followed by an ion-exchange reaction in 1 M HCl solution. The crystalline phase changed from monoclinic hydrogen tetratitanate to an orthorhombic lepidocrocite-type hydrogen titanate by increasing the amount of Cu²⁺ doped. Both compounds could be excited by visible light irradiation (λ>400 nm) and were capable of hydrogen gas evolution from an aqueous methanol solution, where the photocatalytic activity of Cu²⁺ doped hydrogen tetratitanate was slightly greater than that of Cu²⁺ doped lepidocrocite-type hydrogen titanate. The photocatalytic activity of Cu²⁺ doped hydrogen tetratitanate was enhanced by constructing Pt and TiO₂ pillars in the interlayer, and the incorporation of Pt in Cu²⁺ doped hydrogen tetratitanate enabled the cleavage of water into hydrogen and oxygen by irradiating visible light (λ>400 nm) without a sacrificial hole acceptor.     

Recombination luminescence of CaI<Subscript>2</Subscript> crystals activated with Eu<Superscript>2+</Superscript>, Gd<Superscript>2+</Superscript>, Tl<Superscript>+</Superscript>, Pb<Superscript>2+</Superscript>, and Mn<Superscript>2+</Superscript>

The spectral characteristics of thermostimulated luminescence, steady-state roentgenoluminescence and photostimulated luminescence (PSL) buildup and decay kinetics, and the effect of IR irradiation on the roentgenoluminescence yield and glow curves of CaI₂:Eu²⁺, CaI₂:Gd²⁺, CaI₂:Tl⁺, CaI₂:Pb²⁺, CaI₂:Mn²⁺, and CaI₂: Pb²⁺, Mn²⁺ crystals grown by the Bridgman-Stockbarger method have been studied in the temperature range 90–295 K. Coupled with earlier data, the present results on the influence of oxygen and hydrogen impurities on the spectral characteristics of CaI₂ indicate that the activation of calcium iodide with Eu²⁺, Gd²⁺, Tl⁺, Pb²⁺, and Mn²⁺ leads to the formation of cation impurity-native defect complexes, which act as carrier traps and are responsible for the thermostimulated luminescence in the range 150–295 K. IR exposure after 90-K x-ray excitation gives rise to flash PSL and influences the thermostimulated luminescence light sum. The nature of the emission and trapping centers involved and the mechanisms of recombination luminescence excitation in the crystals are discussed.     

Effects of a site substitution of bivalent ions on Ag(Nb0.8Ta0.2)O3 ceramics

Bivalent ions equivalent substitution and equimolar substitution for Ag⁺ in silver niobate tantalate ceramic were studied, which will result in Ag_0.98A_0.01(Nb_0.8Ta_0.2)O₃ and Ag_0.98A_0.02 (Nb_0.8Ta_0.2)O₃ respectively, where A²⁺ = Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cu²⁺, Pb²⁺. The samples were synthesized by traditional solid method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of a little Ag⁺ (in mol ratio 2 %) on the dielectric properties in Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Cu²⁺, Pb²⁺ substituted samples, and the influences of radius and ionic electronegativity on the dielectric properties were discussed. The results showed that the substitution of most bivalent ions except large Ba²⁺ ions for a little Ag⁺ (in mol ratio 2 %) showed no obvious change on the perovskite structure and microstructure of Ag(Nb_0.8Ta_0.2)O₃ ceramics. Basically, the dielectric properties of equivalent substituted samples were better than that of equimolar equimolar substituted samples, Ca²⁺ equivalent substituted samples showed lower dielectric loss, and Cu²⁺ equivalent substituted samples showed higher dielectric constant.     

Zero resistance at 117 K in Bi1.6Pb0.4Sr2Ca2Cu2+xOy compounds

In the Pb-doped Bi-Sr-Ca-Cu-O system, optimization of the composition and heat treatment conditions at which a greater amount of the high-T _c phase forms has been reported in our early paper [1], where the temperature of zero resistance was 107K. Recently, we have achieved zero resistance at 117 K and observed an a.c. susceptibility step at around 150 K by changing the Cu composition in the Bi^1.6Pb^0.4Sr²Ca²Cu^2+x O ^y system (x=0, 0.4, 0.8, 1.2, and 1.6).     

Luminescence of Pb<Superscript>2+</Superscript> in MAl<Subscript>2</Subscript>B<Subscript>2</Subscript>O<Subscript>7</Subscript> (M = Ca,Sr)

Pb²⁺ doped SrAl₂B₂O₇ was prepared by solution combustion synthesis. The synthesized material was determined by powder XRD. The photoluminescence properties of the synthesized phosphor were investigated at room temperature using a spectrofluorometer. The emission peak of Pb²⁺ doped SrAl₂B₂O₇ was observed at 420 nm upon excitation at 277 nm. The Stokes shift of SrAl₂B₂O₇:Pb²⁺ was calculated to be 12 292 cm⁻¹. The luminescence behavior of Pb²⁺ in both SrAl₂B₂O₇ and CaAl₂B₂O₇ was discussed. The text was submitted by the authors in English.     

ESR of Cu2+and Tl2+ in thallium borate glasses

The electron spin resonance (ESR) and optical absorption spectra of Cu²⁺ were measured in thallium borate glasses in order to investigate the effects of glass transition temperature,T _g, upon the responses of cupric ion in alkali borate glasses. The ESR of Tl²⁺ induced by-ray irradiation was also obtained. An abrupt increase in the covalency of in-plane Cu²⁺-O-bonding was observed in the Tl₂O system as well as in the Na₂O system in a similar B₂O₃ composition range althoughT _g for the Tl₂O glasses has little dependency on the composition compared with the Na₂O glasses. The trend in the variation of the S-character of the Tl²⁺ unpaired electron with composition agreed with that of the covalency of in-plane Cu²⁺-O-bonding. The structure of the anion group present in Tl₂O glasses was also examined by laser reman spectroscopy.     

钙系磷酸盐化学键合材料的制备及其固化重金属研究

利用富含氧化钙的铬铁渣(FS)和磷酸二氢钾(P)反应制备钙系磷酸盐化学键合材料,并用其作为固化重金属离子(Pb~(2+)、Cd~(2+)、Cu~(2+))基体材料。研究了原料配比、缓凝剂及重金属掺量对胶凝材料初凝时间和抗压强度的影响。结果表明:当P/FS(质量比,下同)为1/4及硼砂掺量为2%时,材料性能最好,自然养护28d和常压蒸汽养护24h抗压强度分别可达25.65 MPa和36.86 MPa。随着重金属掺量的增加,材料抗压强度逐渐降低,掺量为3%时,自然养护28d和蒸汽养护24h试块抗压强度均大于10 MPa,满足建筑材料要求。固化体重金属毒性浸出试验表明:磷酸盐化学键合材料对重金属离子(Pb~(2+)、Cd~(2+)、Cu~(2+))均具有很好的固化效果,浸出浓度远低于相应的鉴别标准。通过XRD、SEM和FTIR分析,钙系磷酸盐化学键合材料固化重金属的机理是通过水化产物的化学键合、吸附以及物理包裹作用将Pb~(2+)、Cd~(2+)、Cu~(2+)固化在材料中。     

Diffusion mechanism of Co2+, Cu2+, Cd2+, Cs+, and Pb2+ ions in the particles of polyaniline silicotitanate

ABSTRACT

The kinetic behavior of Co²⁺, Cu²⁺, Cd²⁺, Cs⁺, and Pb²⁺ in the H-form of polyaniline silicotitanate composite as cation exchanger was studied as a function of particle size, concentration of the exchanging ions, reaction temperature, and drying temperature. The exchange rate was controlled by particle diffusion mechanism as a limited batch technique and is confirmed from the straight lines of B versus 1/r² plots. The values of diffusion coefficients, activation energy, and entropy of activation were calculated and their significance was discussed. The data obtained have been compared with that reported for other organic and inorganic exchangers.     

Phase formation and microwave dielectric properties of Pb2+ and Sr2+ doped La4Ti9O24 ceramics

Phase formation and microwave dielectric properties of the Pb²⁺ and Sr²⁺ doped La₄Ti₉O₂₄ ceramics were investigated. Using electron diffraction and Rietveld analysis of the X-ray powder diffraction patterns, we show that the increase in the concentration of Pb²⁺ and Sr²⁺ doping results in the structural transition from La₄Ti₉O₂₄ to a La_2/3TiO₃-type phase (Ibmm, No. 74). A change in the crystalline phase considerably affects the microwave dielectric properties, increasing the ɛ_r from 37 to 130, reducing Q × f from 25,000 to 5500, and increasing temperature coefficient of the resonant frequency (TCF) from 15 to 300 ppm/°C.     

Spectroscopic and transport studies of Cu2+ ion doped in (40 —x)Li2O—xLiF—60Bi2O3 glasses

The preparation of (40-x)Li₂O-xLiF-60Bi₂O₃ glassy system and spectroscopic and transport studies of this system are reported. IR results show that this glass consists of [BiO₃] units and indicate formation of Bi-F bonds with the addition of LiF. From the ESR spectra of Cu²⁺ ion, the effectiveg values are found to vary slightly with increasing concentration of fluorine ion. The optical absorption peak corresponding to Cu²⁺ increased linearly with increasing concentration of LiF between 620 nm and 728 nm except at 2.5 mole% of LiF where its value is 729 nm. This peculiar behaviour is attributed to the varying structural coordination of fluorine as the concentration of lithium fluoride is increased. The ionic conductivity measurements indicate that the conduction is due to adiabatic hopping of polarons and the activation energies are found to be temperature and concentration dependent