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In this paper, the effects of M = Mn and Ru substitutions at the Tl site of Tl1−xMx(BaSr)CaCu2O7 (Tl-1212) on the electrical properties and AC susceptibility were investigated. The X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) methods were used to examine the phase and microstructure, respectively. All samples showed diffraction patterns with Tl-1212 as the major phase and an increase in the Tl-1223 phase with increasing Mn and Ru substitutions. The microstructure showed partial melting and randomly oriented grains in all samples. The electrical resistance measurements showed metallic normal state behavior for all samples. The zero-resistance transition temperature Tc−zero was the highest for x = 0.4 where Tc−zero was 107K and 90K for Mn and Ru substitutions, respectively. The superconducting transition, Tcχ′ obtained from AC susceptibility measurements increased with Mn and Ru substitutions up to x = 0.4. Using Bean’s model, the current density at the peak temperature of the imaginary part of the AC susceptibility, Jc(Tp) was determined to be between 16 and 22A⋅cm−2 for Mn, and between 15 and 19A⋅cm−2 for Ru-substituted samples. Mn substitution showed a higher transition temperature compared with Ru. This study showed that optimization of the average Cu valence was achieved with Mn and Ru substitutions for x = 0.4 at the Tl site. The ionic radii of the substituting and substituted elements are important factors in enhancing the transition temperature of Tl(BaSr)CaCu2O7 superconductor. [ABSTRACT FROM AUTHOR]

The local structure of a transition metal (TM) ion is a function of cation elements and valence states. More than that, in this work, by employing a trove of first-principles data of TM oxides, the local structures of TM cations are statistically analyzed to extract detailed information about cation site preference, bond length, site structural distortion, and cation magnetization. It is found that cation radius alone poorly describes the local structure of a transition metal oxide, while the statistics of coordination number as well as the TMO bond length distribution, especially that of the 3d TMs, can provide comprehensive knowledge for understanding the behavior of TM elements. Based on these statistics, the interplay of site distortion due to the Jahn-Teller effect, cation site similarity, and a new set of ionic radii are all obtained to chart the "persona" of transition metal ions in solids.

La3+ and Al3+ loaded D151 resin [R‐La and R‐Al, respectively] were used as salt‐resistant resins for the efficient adsorption of glyphosate. The results showed that La3+ with a larger ionic radius could accommodate more glyphosate as ligands, resulting in higher glyphosate adsorption capacity of R‐La than that of R‐Al. Both R‐La and R‐Al exhibited maximum adsorption capacities at pH 2.52, where glyphosate existed in its ionization equilibrium of pKa2. Consistent with the larger ionic radius of La3+, R‐La featured larger qm and KL than R‐Al at the same temperature. Owing to the smaller radius of Al3+, the enthalpy values for the coordination adsorption of glyphosate by R‐Al were larger than those of R‐La at the same adsorption capacity. Owing to the smaller radius of Al3+, R‐Al exhibited stronger coordination adsorption for glyphosate and significantly higher salt tolerance than R‐La. The adsorption mechanisms indicated that both R‐La and R‐Al could adsorb glyphosate through the coordination of La3+ and Al3+ with O atoms of the phosphonate group of glyphosate. At a NaCl concentration range of 0–16%, R‐Al featured excellent salt tolerance and highly stable glyphosate adsorption capacity than 330, D301, R‐La, and the 14 adsorbents reported in the literature. [ABSTRACT FROM AUTHOR]

Coal fly ash (CFA) as a potential resource for rare earth elements and yttrium (REY) has attracted extensive attention over the past few years. This paper focuses on studying microwave systems for the leaching of REY from CFA. Leaching parameters including hydrochloric acid (HCl) concentration, microwave heating time, microwave heating rate, and temperature were assessed. The optimal recovery of 74.91% REY, 86.77% light rare earth elements (LREY), and 34.79% heavy rare earth elements (HREY) are obtained at the conditions of 3 M HCl, T = 220°C, heating rate 39°C/min, and leaching time 30 min. The closed microwave system produces hydrogen chloride fluid or hydrogen chloride gas that is easier to react with CFA than hydrogen ions. It was revealed by the analysis of XRD, particle size, porosity, and SEM that fracture development benefits the entrance of leaching reagents into the inner layer of CFA. A positive linear correlation was found between leaching efficiency and REY3+ ionic radius. The stability of the REY-O bond also remains consistent with the ionic radius, leading to behavior differences during the leaching. This work was targeted to provide a theoretical and technological foundation for microwave-assisted HCl leaching for the extraction of REY in CFA. [ABSTRACT FROM AUTHOR]

The low-temperature formation of dolomite (CaMg(CO3)2) is undoubtedly a long and interesting geological problem, which has troubled many researchers for centuries to explore the formation of dolomite. Recently, efforts have been made by synthesizing dolomite analogues such as norsethite (BaMg(CO3)2), PbMg(CO3)2, with Ba and Pb to replace Ca and investigating their reaction pathways. In this study, we reported our efforts to synthesize dolomite-related complex carbonates by using the mechanical ball milling method as a new approach to control the solid–water ratio compared to the commonly used solution method. Two analogues of norsethite and PbMg(CO3)2 have been simply obtained even at stoichiometric molar ratio of Ba/Mg = 1:1 and Pb/Mg = 1:1 with various parameters examined; and product properties including morphology and phase compositions were investigated by a range of techniques, including XRD, SEM-EDS, and FTIR. Finally, we attempted to synthesize dolomite and compared the differences from the synthesis of analogues. In conclusion, we have synthesized norsethite and PbMg(CO3)2 in one step by the ball milling method, which greatly reduces the reaction time compared with the conventional solution method and may provide other choices for the formation of dolomite. [ABSTRACT FROM AUTHOR]

The Ba and Sr bearing Tl(BaSr)CaCu2O7 (Tl-1212) phase is an interesting superconductor. Optimizing the average copper valence can lead to a high transition temperature, Tc. Single elemental substitution can be used to optimize the Cu valence. This work investigated the effects of multivalent Cr and Mo substitutions at the Tl site of Tl1-xMx(BaSr)CaCu2O7 (M = Cr and Mo). The samples were prepared via the solid-state reaction method. The structure and lattice parameters were determined using the X-ray diffraction method (XRD). A field emission scanning electron microscope (FESEM) was utilized to observe the microstructure. The electrical resistance and AC susceptibility were measured to determine the transition temperature. XRD pattern showed a single Tl(BaSr)CaCu2O7 phase for the non-substituted sample. Other phases, such as Tl-1201 and Ca0.3Sr0.7CuO2 were also observed in the Cr and Mo substituted samples. The non-substituted sample showed onset transition temperature, Tc-onset of 108 K. The highest Tc-onset was observed in the Tl0.9Mo0.1(BaSr)CaCu2O7 (115 K) and Tl0.5Cr0.5(BaSr)CaCu2O7 (111 K) samples. The intergranular critical current density was between 17 and 22 A cm−2. Cr substitutions for x = 0.1 to 0.5 and Mo substitutions for x = 0.1 showed the highest transition temperature. These results can be used as guides to improve the superconducting properties of the Tl-1212 phase. [ABSTRACT FROM AUTHOR]

The influence of rare earth ions on layered perovskite (AA'B 2 O 5+δ) is the key to the development of highly active layered perovskite cathode. Herein, we make a systematic explanation through experiment and first-principles calculation. The lattice constant decreases with the decrease of Ln3+ ionic radius, resulting in a smaller space of interstitial oxygen position and increasing oxygen Frenkel energy. The electrochemical activity of LnBaCo 2 O 5+δ (Ln = Pr, Nd and Sm) electrodes decreases with the decrease of Ln3+ ionic radius, which is mainly attributed to a lower oxygen Frenkel energy. Electrochemical impedance spectra tests show that there are significant differences in the surface exchange process of oxygen because of different surface oxygen vacancy concentration for LnBaCo 2 O 5+δ. For Ln = Pr, Nd, and Sm cathodes, the maximum power densities of the anode-supported Ni-YSZ/YSZ/GDC/LnBaCo 2 O 5+δ single cells reach 1.48, 1.36 and 1.06 W/cm2 at 800 °C, respectively, indicating that PrBaCo 2 O 5+δ with the maximum rare earth ion radius exhibits better oxygen reduction reaction. These findings provide guidance for the design and fabrication of highly active layered perovskite electrode materials. [ABSTRACT FROM AUTHOR]

Over several decades, a wealth of literature has been devoted to correlations between the chemistries of phyllosilicates and their crystallographic unit-cell parameter values. The c parameter is currently used because of its relation to the layer-to-layer distance, characteristic of the various families of phyllosilicates. The b parameter is also of interest because it allows measurement of the layer lateral dimensions and inherent structural adjustments. This unit-cell distance can be extracted from X-ray diffraction traces from the (06ℓ;33ℓ) diffraction region and by attributing the main diffraction peak observed to a 060 reflection, leading to the relationship b = 6.d(060). The aim of this paper is to revisit the relationships between the b value (or equivalent) of the phyllosilicate (i.e. TO, TOT and TOTO) or hydroxide (i.e. hydroxide, oxyhydroxide and layered double hydroxide) families and the layer chemistry based on a mean ionic radius R of octahedral cations, calculated as R = ∑i=1n (ri.xi), where ri is the ionic radius of the octahedral cation i and xi is its molar fraction over n types of octahedral cations (∑i=1n (xi) = 1). The data were collected from the literature and involved both natural and synthetic samples with both dioctahedral and trioctahedral structures of the octahedral sheet. The results showed that b values can be linked strongly to R, leading to suitable linear regressions for all of the studied structures. All correlations were found to be applicable irrespective of the di- or trioctahedral nature of the octahedral sheet, and these are discussed in light of (1) the lateral dimension of the octahedral sheet and (2) the dimensional misfit between the tetrahedral and octahedral sheets. For hydroxide families, all data can be gathered on a single b vs R correlation line, and the dimensional properties of the octahedral sheet can be interpreted simply based on an oxygen–cation–oxygen mean distance. For TO structures, two general b vs R correlation trends were reported, and these were assigned to two adjustment mechanisms corresponding to distinct types of tetrahedral and octahedral distortions. For the mica TOT family, two main trends were also reported, whereas the use of the synthetic mica series allowed us to demonstrate that the obtained scattering of data was mainly driven by the presence of multiple limited solid solutions. Such chemical complexity was also noted for smectites, especially regarding the tetrahedral composition and associated variability in layer charge. This variability made it difficult to propose a general regression correlating b to R values for smectites, although the regression obtained for neutral TOT layers can apply as a first-order relation. Finally, a single general b vs R correlation was obtained for chlorites, and the observed slope of the regression was interpreted according to the role played by the isolated hydroxide sheet on the evolution of the lateral dimension of the structures. [ABSTRACT FROM AUTHOR]

This work employed the electrostatic levitation furnace (ELF) apparatus installed in the KIBO Japanese Experiment Module on the International Space Station. The ELF is able to levitate high-melting-point materials such as ceramics without containers. The heating and melting of refractory oxides in this apparatus allows the analysis of various thermophysical properties. including density, surface tension and viscosity. that are otherwise very difficult to measure in terrestrial laboratories. In the present study, the density of molten Y2O3, was determined over a wide temperature range using the ELF. A density of 4700 kg/m³ was obtained at 2712 K, in good agreement with the value previously obtained using an aero-acoustic levitator. The relationship between the ionic radius and the molar volume of liquid Y2O3 was ascertained and found to be similar to those for other non-glass-forming sesquioxides. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Understanding the kinetic process during the self‐assembly and chiral amplification of metal‐organic polyhedra (MOPs) is critical for the rational preparation of chiral MOPs. Herein, we report the ionic radius dependent kinetic processes for the self‐assembly and chiral amplification of Ln4L4‐type (Ln, Lanthanides; L, ligand) lanthanide tetrahedral cages. The chiral Eu4(LR)4 tetrahedral cage is structurally characterized by nuclear magnetic resonance (NMR), electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS), and single crystal X‐ray diffraction. Kinetic study on the stereo‐controlled self‐assembly of circularly polarized luminescence (CPL)‐active Ln4(LR)4 (Ln = LaIII, PrIII and EuIII) tetrahedra manifests that the larger ionic radius of Ln leads to faster assembly rates. Mixed‐ligand cage assembly experiments with chiral LR/S, achiral Lac and Ln (1 : 3 : 4 molar ratio) reveal that the self‐assembly and chiral amplification occur synchronously for the LaIII and PrIII cages, while two distinct steps, i.e., first self‐assembly and then chiral amplification, are observed for the EuIII cage. Such distinct kinetic behavior is attributed to different ligands exchange rates among the mixed‐ligand Ln4L4 cages. This work provides fundamental guidance for fabrication and property‐optimization of chiral lanthanide‐based molecular materials. [ABSTRACT FROM AUTHOR]

The ability of heavy metals to accumulate in living organisms, combined with the fact that they are not biodegradable, necessitates an expansion and improvement of the existing water purification methods. An effective mixing of contaminated water with heavy metals and magnetic nanoparticles is crucial for water treatment applications. In the present work, electromagnetic and shear mixing are combined to explore optimization mixing strategies. Mixing is studied through simulations under various initial conditions for two streams that are loaded with nanoparticles and one contaminated water stream that lies between the nanoparticle streams. In the present work, magnetic mixing is superimposed with a time-modulated gradient external magnetic field. The results show that as the radius ratio between the nanoparticles and the heavy metals increases, the external magnetic field is more effective insofar as the mixing of the nanoparticles is concerned. Moreover, for simulations where the radius ratio is higher than or equal to 10, an effective mixing is achieved. By comparing the velocity ratios, a better mixing is achieved in the case of higher velocity ratios. Also, minor effects on mixing are observed by comparing the ratios Vp/Vc = 10 and Vp/Vc = 20. HIGHLIGHTS We study the mixing optimization of heavy metal contaminated water with magnetic nanoparticles.; The study is performed using Computational Fluid Dynamics (CFD).; Magnetic mixing is combined with a time-varying gradient magnetic field.; Mixing efficiency is enhanced as the radius ratio between nanoparticles and heavy metals increases.; Mixing is affected by the velocity ratio of contaminated water over the nanoparticle current.;

We have studied the electronic structures and thermoelectric (TE) properties of the n -type titled clathrates with alkali metals as guest atoms. Their conduction-band bottoms are strongly influenced by the guest atoms, whose atomic orbital types and ionic radii are important factors. For Na, the guest atoms at the 24-atom cages contribute more than those at the 20-atom cages, but the opposite is true for K and Cs. The location of the electron density connections, that is, the conduction pathways for electrons, change accordingly in the crystal. Also, a lighter alkali-metal element as a guest atom gives a larger density-of-states effective mass due to its s -orbitals. The measured effective masses, mobilities, and TE properties of the clathrate samples were almost consistent with their electronic structures. [Display omitted] • Electronic structures of Ge clathrates with alkali-metal guest atoms were calculated. • They are strongly influenced by s -orbitals and ionic radii of alkali metals. • Carrier conduction pathways are mainly formed by guest-host hybrid orbitals. • Thermoelectric properties were well consistent with electronic structures. [ABSTRACT FROM AUTHOR]

In this work, we apply the concept of tolerance factors (t) to pyrochlore solid solution, particularly when the B-site contains two different ions with different masses (as well as charge states) in the formula unit A 2 3 + B 3 + B ′ 5 + O 7 as in the present sample of A2BSbO7 (A3+ = Y, Dy, Gd, Bi; B3+ = Fe, Ga). We examine the previous tolerance factor and proposed a model of lattice constant (a) that depends only on the ionic radii RA, RB (= R F e + R (S b) 2 or R G a + R (S b) 2 ) and RO. Then we proposed an empirical tolerance factor (t), that depends only on the R A , R B and R O of the constituent atoms. We discuss the structural stability field and property features of mixed pyrochlore oxide compounds before measuring their structural data as for the case of perovskites. In the present work, we have proposed the empirical formula of lattice constant of A2BSbO7 (A3+ = Y, Dy, Gd, Bi; B3+ = Fe, Ga) of formula unit A 2 3 + B 3 + B ′ 5 + O 7 and hence find the tolerance factor, which predict the structural stability field and property features of mixed pyrochlore oxide compounds before measuring their structural data as for the case of perovskites. Caption: Errors (in %) between the calculated and experimental lattice constants. In the above figure, we shown that the errors (%) between the calculated and experimental lattice constants found from empirical lattice formula a = 8 3 1.4474357143 R A + R O - 0.42931 R A + R O 2 (R B + R O) and Rietveld analysis of powder diffraction data respectively. The error of predicting for the lattice constant by Brik and Srivastava (J Am Ceram Soc 95:1454–1460, 2012) is moderately higher than the error (≤ 0.523%) obtains by our model for mixed pyrochlore oxides. [ABSTRACT FROM AUTHOR]

Ag-Al paste is a key material of n-type silicon-based solar cells. The uneven Ag/Al spike on the transmitter surface after metallization is easy to cause local short circuit, which is a bottleneck that limits its application. The glass play an indispensable role in the surface metallization of the emitter. The influence of high temperature wettability and thermal properties of glass on the metallization of p+ emitter was studied from the point of view of ionic radius by adjusting the ratio of Al/Ga. The results indicated that when the Al/Ga ratio is 2:3, an abundance of free oxygen improved the O/Si ratio within the glass network structure, facilitating the depolymerization of siloxane anion cluste rs into simpler structural units in the silicate network structure. Al ions preferentially combine with free oxygen to formed [AlO 4 ]. The entrapment of free oxygen by [BO 3 ] units tended to form more [BO 4 ] units with increased thermal stability. The glass sample demonstrated minimal difference between left and right contact angles. The glass wet the Si wafer steadily and evenly throughout the melting process. The formation of a continuous dense glass layer increased the contacts between the metal electrode and the emitter. Not only a mass of silver crystals were deposited on the emitter surface, but also small and dense Ag/Al spikes were distributed. Excellent metallization contacts were formed with the p+ emitter, which improved the solar cell's photoelectric conversion efficiency. • The ratio of Al 2 O 3 to Ga 2 O 3 was 2:3, which improved the high temperature wettability and thermal stability. • The optimal high temperature wettability of the glass increased the contacts with the p+ emitter. • The [AlO 4 ] promoted the deposition of Ag/Al spikes, forming an optimal metallization contact. [ABSTRACT FROM AUTHOR]

This paper presents the results of studying the effect of the isomorphic substitution of Y3+ ions into Gd3+ ions on the structure and luminescent properties of yttrium-aluminum garnet nanopowders activated with Yb3+ ions obtained by the polymer-salt method. To study the structure of the material, the methods of X-ray phase analysis, as well as luminescent and infrared spectroscopy, were used. It is established that with an increase in the content of the Gd3+ ions in the garnet structure, a monotonic expansion of the unit cell of crystals and an increase in the width of the Yb3+ luminescence band are observed. [ABSTRACT FROM AUTHOR]

The technology of synthesis of inorganic binder material based on sodium tripolyphosphate Na5P3O10 and orthophosphoric acid has been developed. The sequence of physicochemical transformations in this system, as well as the optimal mass ratio of orthophosphoric acid and sodium tripolyphosphate are established. The research uses methods of quantitative and qualitative X-ray phase analysis, differential thermal analysis, standard methods of testing samples for compressive strength. The ratios of the atomic radii of the cation (Na) and the anion (P2O7), as well as the presence of hydrogen bonds, provide a significant increase in the binding potential compared to other sodium phosphates. It was found that the strengthening of mixtures with 2…8 mass parts including sodium pyrophosphate, the filler of which is quartz-based sand, occurs as intensely as possible when heated to 150°C. A further increase in temperature above 250 °C leads to the conversion of sodium pyrophosphate to ordinary (non-polymeric) metaphosphate NaPO3, which exists without changes in chemical structure up to 1000°C. The developed binder material, given the global trends of decarbonization and resource conservation, is a competitive alternative to widely used synthetic resins and other organic materials. It does not contain harmful substances and does not emit dangerous products when heated.

The Sr and Ba bearing Tl-1212 phase, Tl(Ba,Sr)CaCu 2 O 7 is an interesting superconductor. The Sr only bearing TlSr 2 CaCu 2 O 7 is not easily prepared in the superconducting form. The Ba only bearing TlBa 2 CaCu 2 O 7 on the other hand does not show improvement in the transition temperature with elemental substitution. In this work the influence of multivalent Se (non-metal) and Te (metalloid) substitutions at the Tl-site of Tl 1- x M x (Ba,Sr)CaCu 2 O 7 (M = Se or Te) superconductors for x = 0–0.6 was studied. The samples were prepared via the conventional solid-state reaction method. XRD patterns showed a single Tl-1212 phase for x = 0 and 0.1 Se substituted samples. The critical current density at the peak temperature, T p of the imaginary (χ") part of the AC susceptibility (χ = χ' +χ"), J c-inter (T p) for all samples was between 15 and 21 A cm−2. The highest superconducting transition temperature was shown by the x = 0.3 Se-substituted sample (T c-onset = 104 K, T c-zero = 89 K, T cχ' = 104 K and T p = 80 K). Te suppressed the superconductivity of Tl-1212 phase. The order of highest transition temperatures are as follows: Tl 1- x Te x (Ba,Sr)CaCu 2 O 7

Microwave combustion technique (MCT) was used to synthesize of spinel Ni1-xSrxFe2O4 (x = 0.0, 0.1, 0.3 and 0.5) nanoparticles (NPs) by employing the fuel L-arginine. The physical characteristics of the as-prepared NPs were obtained by following methods, viz., powder X-ray diffraction (XRD), high-resolution scanning electron microscope (HR-SEM), energy-dispersive X-ray (EDX), UV-visible diffuse reflectance spectra (UV-Vis DRS), Fourier-transform infrared spectra (FT-IR), and vibrating sample magnetometer (VSM) techniques. The diffraction studies revealed that the average crystallite size exists in the band of 14.25 to 27.52 nm. The HR-SEM pictures revealed the agglomerated and spherical morphology of spinel Ni1-xSrxFe2O4 (x = 0 to 0.5) nanoparticles. Elemental analysis ensured the existence of Ni, Sr, O, and Fe ions. The energy band gap of the NPs was observed to exist in the range of 2.95 to 3.39 eV upon varying the concentration of Sr2+ dopant. The broad peaks at 437 cm−1 and 582 cm−1 correspond to octahedral (B-) metal stretching (Ni-O) and tetrahedral (A-) metal stretching (Fe-O) of nickel ferrite respectively. Magnetic results revealed that the prepared NPs are ferromagnetic in nature. The antibacterial activity (ABA) of gram-positive Staphylococcus aureus and Bacillus subtilis and gram-negative Escherichia coli and Klebsiella pneumonia has been investigated using pure and Sr2+-substituted NiFe2O4 NPs. It was found that the improved activity is intensified with smooth Sr2+ doping as it causes a decrease in the grain size. [ABSTRACT FROM AUTHOR]

Cerium and cerium-based oxides are found to be an important element in three-way catalytic converter (TWC). The effective utilization of TWC is found to be reduced due to thermal loading which results in structural deformation of ceria. Doping Zr4+ into the rare earth element can increase the oxygen storage capacity and thermal stability. Hence, an attempt was made to study the oxygen storage capacity and thermal stability of ceria by doping Zr4+ and Nd3+. Cerium-based nanocrystallite in the composition of Ce0.6Zr0.4−xNd1.3xO2 (0 ≤ x ≤ 0.4) was prepared by sol–gel synthesize technique with citric acid as a gel-forming agent. X-ray diffraction (XRD) result shows that doping Nd3+ into ceria lattice forms homogenous solid solution of cubic fluorite structure up to 25 % of substitute only. Doping higher amount of Nd3+ into ceria lattice leads to the formation of Nd2O3. Raman spectrum study confirms that oxygen storage capacity band is present in Ce0.6Zr0.4O2 and Ce0.6Zr0.3Nd0.13O2. The oxygen storage capacity was calculated through weight loss of the sample during the second heating cycle with cyclic heating from 30 to 800 °C in thermogravimetric analysis (TGA). The TGA study reveals that the oxygen storage capacity of Ce0.6Zr0.4O2 decreases after the substitution of Nd3+, which is due to the larger ionic radius of Nd3+ compared with that of Zr4+ and CeO2. [ABSTRACT FROM AUTHOR]

This review is on the effects of elemental substitutions at the Tl-site of TlSr 2 CaCu 2 O 7 (Tl-1212) superconductor. The objective of this paper was to determine the elements that enhance or suppress the superconducting transition temperature, T c of (Tl 1- x M x)Sr 2 CaCu 2 O 7 phase. The elements included in this review were M = Pb, Bi, Cr, V, Re, Zr, In, Er, Gd, Na, K, Rb and Se. The relations between transition temperature and the ionic radius, coordination number, valence state and optimization of the hole concentration of the selected elements were studied. The preparation methods, sintering temperature, Tl-1212 phase and structural stability were also discussed. All alkali metals (K, Na and Rb) suppressed the transition temperature of the Tl-1212 phase. The transition temperature generally decreased linearly with ionic radius except for Cr which showed the highest T c although its ionic radius is smaller. [ABSTRACT FROM AUTHOR]

The addition of low melting point trivalent ions in ceria-based electrolyte systems results in a new composite with better oxygen ion conduction at reduced temperature. The present work discusses the synthesis and characterization of co-doped ceramic electrolyte Ce0.8Sm0.1M0.1O2−δ (M = Bi, Sb) prepared by coprecipitation. This study mainly focuses on the effect of the ionic radius of the dopants on the structural and electrical properties of doped ceria. The structural studies of the samples by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy show nanosized particles with a cubic fluorite structure. Raman spectroscopy confirmed the presence of O2− vacancies introduced into the lattice due to the substitution of a large ionic radius of Bi3+ for Ce4+. The electrical survey by electrochemical impedance spectroscopy suggests that the dopant ionic radius has a significant influence on the ionic conductivity and activation energy of the doped ceria. There is an enhancement in conductivity noted for bismuth-co-doped samarium-doped ceria due to the larger ionic radius of the bismuth dopant compared to antimony-co-doped samarium-doped ceria. [ABSTRACT FROM AUTHOR]

In this work, chabazite SSZ-13 samples with different cations were synthesised by hydrothermal method and thoroughly analysed using various characterisation techniques. The role of types of cations in CO2 and CO adsorption measurements was investigated. The adsorption isotherms were fitted by Langmuir, Langmuir-Freundlich and Toth adsorption models, respectively. The result shows that the Langmuir-Freundlich model is the most suitable for the adsorption isotherms of SSZ-13 molecular sieves. The adsorption isotherms of the fitted CO2 and CO were analysed to study the high silicon SSZ-13 samples of alkali metal cations Li+, Na+, K+ and Cs+ for ion exchange. The result shows that Na+ has the highest adsorption capacity, but the adsorption selectivity is extremely low. K+ has the lowest adsorption capacity, but it has excellent adsorption selectivity, which may be attributed to its large cation radius and the special position of cations in CHA skeleton structure, resulting in the formation of 'molecular trapdoor' effect. In addition, Cs+ has a larger ionic radius than K+, but the adsorption selectivity is not significantly improved, similar to Li+. It can be determined that the 'molecular trapdoor' effect has a significant relationship with the position of cations in the framework. [ABSTRACT FROM AUTHOR]

So far, it has rarely been acknowledged that the initial version of the Debye-Hückel theory provided for different mean distances of closest approach to different ions, but the final formulation of the theory was presented with a single geometric parameter for all the ions in a solution. Here the initial design is recalled by deriving the Debye-Hückel equation for the mean activity coefficient in binary solutions with two geometric parameters for the two ion species present and, in the course of this, looking critically at details of the derivations. The equation is compared with the SiS model of electrolyte solutions (Mol. Phys. 108, 1435 (2010)) both in theoretical aspects and as regards their abilities to reproduce experimental data. It is found that the SiS model, as distinct from the original theory, is thermodynamically inconsistent in that it derives the mean activity coefficient from chemical potentials of ions, which do not represent partial derivatives of a single free-energy function of the solution. In addition, arguments are set forth that the geometric parameters in both equations cannot be interpreted in terms of a realistic structural chemistry. The results of comparing the two equations with experiment are found to bear out this view. [ABSTRACT FROM AUTHOR]

(A, B) co-doped TiO 2 ceramics attract great interests due to the excellent dielectric properties. In this work, the (A, Ta) co-doped TiO 2 ceramics were prepared by a solid state reaction process. The effect of the acceptors ionic radius on the structure and properties of TiO 2 ceramics was investigated. According to XRD analysis, the main phase is rutile TiO 2 for all samples. Due to the larger ionic radius, it is hard to replace Ti site in TiO 6 octahedron. As a result, the content of the secondary phase increased with increasing ionic radius. The dielectric properties were significantly enhanced by co-doping of alkaline-earth ions and tantalum ions, and the best dielectric constant obtained at 3% (Sr, Ta) co-doped compositions, where ε' = 2.1 × 105, tanδ = 0.21. Meanwhile, the XPS analysis suggested that the concentration of the defect dipoles exhibit a maximum in Sr-doped TiO 2 ceramics. The larger ionic radius of the acceptors leads to the more stability of the defect structure. However, for Ba ions, the replacement concentration decreased due to the excessive ionic radius, which in turn reduces the defect concentration. This work is meaningful for the further investigations on TiO 2 -based colossal permittivity materials. [ABSTRACT FROM AUTHOR]

Polymer polyelectrolyte hydrogel composites of acrylic acid and acrylamide copolymer filled with different amounts of bentonite (from 1 to 5 wt.%) were synthesized. Collapse kinetics of hydrogel composites was studied in solutions of different concentrations of polyvalent metal salts at a constant temperature of 25 °C. The mass of water given away from hydrogels into the solution was determined by gravimetric method. It has been found that the presence of bentonite in the polyelectrolyte hydrogel composites prevents to some extent collapse in electrolyte solutions, due to steric and electrostatic interactions between the filler particles. These interactions preclude further collapse of hydrogels. The Peleg's kinetic model, most precisely describing experimental data, was applied to calculation of kinetic constants of polymer hydrogels collapse. It is shown that the initial collapse rate and the kinetic constant of collapse and swelling depend non-monotonically on the concentration (ionic strength) in the electrolyte solution. At the identical concentration of salts in the solution the kinetic constant of hydrogel collapse is independent of the radius of ions of metals of the studied salts.

The crystal structures of chelates formed between each stable paramagnetic lanthanide ion and the octadentate polyamino carboxylate ligand DOTMA are described. A total of 23 individual chelates structures were obtained; in each chelate the coordination geometry around the metal ion is best described as a twisted square antiprism (torsion angle −25.0°–−31.4°). Despite the uniformity of the general coordination geometry provided by the DOTMA ligand, there is a considerable variation in the hydration state of each chelate. The early Ln3+ chelates are associated with a single inner sphere water molecule; the Ln‐OH2 interaction is remarkable for being very long. After a clear break at gadolinium, the number of chelates in the unit cell that have a water molecule interacting with the Ln3+ decreases linearly until at Tm3+ no water is found to interact with the metal ion. The Ln‐OH2 distance observed in the chelates of the later Ln3+ ions are also extremely long and increase as the ions contract (2.550–2.732 Å). No clear break between hydrated and dehydrated chelates is observed; rather this series of chelates appear to represent a continuum of hydration states in which the ligand gradually closes around the metal ion as its ionic radius decreases (with decreased hydration) and the metal drops down into the coordination cage. [ABSTRACT FROM AUTHOR]

Abstract In the work, Al, La, Ce and Sn were introduced to investigate effects of A/B-site dopants on microstructure and domain configuration of KNN-based piezoceramics. The results of XRD analysis showed that O phase and T phase coexisted in all the samples and A-site dopants gave rise to expansion of O phase and shrinkage of T phase while B-site dopants played an opposite role in lattice deformation. Moreover, the samples with B-site dopants possessed big c / a which was closely related to T c. Some step-like grains and the grains with fish-bone stripes were generated in all the samples because the dopants with different melting point influenced grain growth behavior significantly through changing some special crystal faces' growth velocity. Besides, it was verified that high melting point facilitated formation of nanodomains and a novel domain configuration was reasonably deduced according to special spatial orientation of lattice planes observed by HR-TEM in O-T phase coexistence region. In conclusion, comparable piezoelectric properties (d 33 ∼200 pC/N etc.) to K 0.5 Na 0.5 NbO 3 -Bi 0.5 Na 0.5 ZrO 3 were attained in Al doping ceramics, implying appropriate substitution of Al for Bi was beneficial to lower the cost. [ABSTRACT FROM AUTHOR]

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The lead halo borate glasses with composition xPbBr2 - (30-x)PbO - 68B2O3 - 2V2O5 (where ≤ x ≤ 25 mol%) were prepared 2 2 3 2 5 by using melt quenching technique. Physical and optical properties were investigated with increasing PbBr content. Using X-Ray Diffraction (XRD), amorphous nature of glass samples is confirmed. Archimedes principle is used to determine the density of the glass samples. When oxygen ions are replaced by bromine ions the density is found to decrease. The ionic radii of bromide ions played an important role in explaining the physical properties like density and molar volume. Optical band gap and Urbach energy values were evaluated from optical absorption spectra. Using these values refractive index, molar refraction and molar electronic polarisability were determined. FTIR analysis was employed to explore the impact of lead bromide on the structure of lead borate glasses. [ABSTRACT FROM AUTHOR]

This study investigated the adsorption behavior of selected heavy metals (Pb, Cu, and Ni) under single and multi-metal conditions by a light textured calcareous soil amended with plant residue biochars (corn straw, wheat straw, rice husk and licorice root pulp each at 3% w/w). The Freundlich isotherm best described the heavy metal adsorption suggesting multilayer adsorption. For all treatments under both adsorption conditions, the heavy metal adsorption capacity followed the order of Pb > Cu > Ni, which was associated with the hydrolysis constant, ionic radius, and electronegativity of these metals. Simultaneous presence of multiple metals decreased the adsorption capacity for each metal and the sequence was in the order of Ni > Pb > Cu. The corn straw biochar (CSB) had the highest adsorption capacity (Freundlich Kf (mg g−1) for Ni = 0.23, Cu = 1.41 and Pb = 2.73) and medium distribution coefficient (Kd medium(L kg−1) for Ni = 59.30, Cu = 1961.00 and Pb = 2602.00), indicating the CSB is the best treatment for stabilization of heavy metals in the soil. This was associated with the chemical characteristics of the CSB (high amounts of CaCO3 and P) and the greatest increase in soil pH value. [ABSTRACT FROM AUTHOR]

Phase equilibria in the binary system NaCl-RaCl2 were predicted based on the binary systems NaCl–MCl2 (M = Ca, Sr, Ba). All the considered systems are of the eutectic type. Experimental data were processed, and functional dependences Te/Z = f(Z) and Te/r = f(r) were obtained, where Te is the melting point of the eutectic in the binary systems NaCl–CaCl2, NaCl–SrCl2, and NaCl–BaCl2; Z is the atomic number of Ca, Sr, or Ba; and r is its ionic radius. By further calculations using these functions, the melting point of the eutectic in the NaCl–RaCl2 system was found. Using the Schröder–Le Châtelier equation, the composition of the binary eutectic in the predicted system and the molar enthalpy of melting of RaCl2 were calculated, and branches of the liquidus of the system were constructed. [ABSTRACT FROM AUTHOR]