Use of solid electrolyte GeSe-GeI<Subscript>2</Subscript> for electrochemical doping with germanium

Lead tellurite is study to show that solid electrolyte GeSe-GeI₂, which has the optimum composition and contains 5 mol % of GeI₂, can in principle be used for electrochemical doping of semiconducting materials with germanium by the coulometric titration method. Some parameters of the coulometric titration are considered. The doping efficiency is monitored by determining variations in the concentration of charge carriers using the Hall method and by measuring the EMF of corresponding galvanic cells.     

Electrochemical sensors for sulfur- and lead-containing gases

The possibility of using solid-electrolyte transducers with nonstoichiometric electrodes was studied, and the effect of the material and nonstoichiometry of lead monochalkogenides as measurement electrodes on the work of transducers was considered. The reliability of the results obtained was substantiated by comparing the calculated thermodynamic properties of the measurement electrodes with the corresponding reference values. The effect of nonstoichiometry was assessed from coulometric titration curves. It was noticed that the defect type affects the sensitivity of the transducer. The effect of the surface of the measurement electrode on the process of gas analysis was assessed. The applicability region for the transducers under study was indicated.Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 2, 2005, pp. 193–197.Original Russian Text Copyright © 2005 by Leushina, Makhanova.Presented at the International Forum Analytics and Analysts, Voronezh, 2003.This revised version was published online in April 2005 with corrections to the author names and book review format.     

Transport and Conduction Properties of Solid Electrolyte CuCl–CdCl2 in the Region of Solid Solutions

In quasi-binary salt system CuCl–CdCl₂ where CuCl is the basis compound and CdCl₂ is the additive, maximum values of electroconductivity, ion transport number, and diffusion coefficient are determined at 20–30 mol % CdCl₂, which points to a maximum ionic disordering. Character of ionic disordering is discussed and predominant conduction by copper(I) ions is proved. X-ray diffraction analysis shows the formation of CuCl-based solid solutions at 20–30 mol % CdCl₂. The current efficiency is close to 100%, which guarantees that Faraday's laws are obeyed during coulometric titration of CuCl–CdCl₂ of optimum compositions in cells containing a solid electrolyte. The CuCl–CdCl₂ system is found to have good ceramic properties. Electrolytic and working characteristics can be stabilized at low temperatures by decreasing hydrolyzability and oxidizability of the solid electrolyte after adding a dopant.     

Selecting indium-containing systems as solid electrolytes

Quasi-binary salt systems InCl₃-MeCl₂, where Me²⁺ stands for Mg²⁺, Cd²⁺, Zn²⁺, Sn²⁺, Co²⁺, or Mn²⁺, in the region of solid solutions on the basis of InCl₃ are considered. A comparative characteristic of some transport properties of these systems is given and optimum compositions for all systems under consideration are determined. The conduction mechanism that presumably takes place in systems InCl₃-MgCl₂ and InCl₃-CdCl₂ is confirmed by data that are obtained with the aid of the Tubandt method. In order to raise the reversibility with respect to the indium ion, also considered is the In₂S₃-InCl₃ system, in which the basis compound is In₂S₃. Methods of electroconduction and XRD are used to establish the existence of a region of limited solid solutions on the basis of indium sulfide. The current efficiency in a system with solid electrolyte In₂S₃-InCl₃ is determined (CE > 50%) and the dependence of the current efficiency on the electrolysis regime is considered. Thermodynamic investigation of some indium-containing compounds and the doping with indium are conducted with use made of indium-containing solid electrolytes of optimum compositions. Data concerning the magnitude of the alteration occurring in the Gibbs energy during the formation of indium-containing semiconducting compounds, which are close to reference data, are obtained.     

Determination of the Selectivity of Electrodes Made of a Mixture of Nonstoichiometric Silver and Copper(I) Sulfides in the Analysis of Sulfur-Containing Aqueous Solutions

The possibility of using electrodes made of a mixture of nonstoichiometric silver and copper(I) sulfides in the analysis of sulfur-containing aqueous solutions by direct potentiometry and potentiometric titration was assessed. The selectivity coefficients of the electrodes under study to chloride and iodide ions were determined. The effect of pH on the performance and conductivity of electrodes was studied.     

Electrochemical Sensors for Sulfur- and Lead-Containing Gases: Effect of Nonstoichiometry of Measuring Electrodes

In accordance with the fact that the region of homogeneity of lead sulfide is two-sided, i.e. it includes compositions with both sulfur excess and lead excess relative to the stoichiometric composition, it is shown that a sensor with a Pb_{1 ±} S measuring electrode (ME) may be used for analyzing both sulfur- and lead-containing media. The general principle of operation of electrochemical sensor Me, Pb/PbCl₂–CaCl₂/Pb_{1 ±} S, is based on measuring EMF of an electrochemical circuit with a lead-conducting electrolyte at a specified sulfur vapor pressure above the reference electrode. At a fixed temperature, the cell's EMF is uniquely defined by the sulfur content on ME. The studies are done in the temperature interval 285 to 300°C where characteristics of the solid electrolyte used are optimum; its upper boundary is limited by mp of the lead reference electrode (327°). The interval of determinable concentrations of sulfur- and lead-containing gases is 10^–1 to 10^–9 vol %. If analysis is performed in a dynamic mode (in a carrier gas flow), the limiting stage is the adsorption of gas molecules on the ME surface and the sensor sensitivity increases after modifying the surface by various techniques and also due to the ME composition altering only in a surface layer. The sensor's working characteristics are affected mostly by the degree of deviation of the ME material from stoichiometry.     

Synthesis of phosphine-containing dipyrromethene cobalt complexes,promising ligands for homogeneous catalysis in nanomembrane reactors

Complexes of 5-(4-diphenylphosphinophenyl)dipyrromethene with trivalent cobalt (Ph₂PC₆H₄DP)₃Co (DP for dipyrromethene) were obtained for the first time, and their reaction with dicarbonylrhodium(I) acetylacetonate was investigated. The formed complex [Ph₂P(Rh)C₆H₄DP]₃Co was characterized by ¹H, ¹³С, and ³¹P NMR spectroscopy. The dimensions of the ligand were estimated (by geometry optimization with PM3 method) and of the formed rhodium complex (by 2D diffusion NMR spectroscopy DOSY). The size of the complex makes it possible to detain it on membranes with the pore size of 2 nm providing an opportunity to use it in catalytic processes with subsequent separation of the catalyst and the reaction products in the nanofiltration mode. Test of 1-octene hydroformylation with the use of this catalytic system showed results similar to those with the system Rh–PPh₃ both with respect to conversion in aldehydes and to the ratio of n/iso-products. Thus the fundamental possibility was demonstrated of applying the synthesized complexes in catalysis.     

Dependences on the Composition and a Comparison of Electrolytic Properties of Some Germanium-Containing Quasi-binary Salt Systems

Germanium-containing quasi-binary salt systems GeSe-GeI₂ and NaI-GeI₂ (GeI₂ is a dopant) are studied by methods of electroconductance and x-ray diffraction analysis (XRDA). The conductivity isotherms combined with the XRDA data show that the domain of restricted solid solutions in these systems comes to 3 and 1 mol % GeI₂, respectively. The maximal electrolytic admittance is observed at 2 and 0.25 mol % GeI₂ in GeSe-GeI₂ and NaI-GeI₂ systems. The GeSe system has better ceramic properties, is less susceptible to water traces, and has higher conductivity and lower activation energy for conduction.__________Translated from Elektrokhimiya, Vol. 41, No. 5, 2005, pp. 616–619.Original Russian Text Copyright © 2005 by Leushina, Danilov, Zlomanov.     

T-x diagram and transport properties of the GeSe-GeI2 solid electrolyte

The T-x diagram for the GeSe-GeI₂ system was plotted based on DTA, XRD, and conductivity data. The diagram features a simple eutectic and a limited region of solid solutions with prevalent GeSe content. It was established that, in the region of solid solutions, the properties of the GeSe-GeI₂ solid electrolyte are substantially dependent on the concentration of the GeI₂ dopant. The highest conductivity (10^?3?10^?4 S/cm at 150°C), lowest activation energy of electric conduction (0.3–0.4 eV), and lowest electronic (hole) transport numbers (10^?5?10^?7 at 150°C) at high ionic (～1.0) and cationic (0.9–1.0) transport numbers were observed at a GeI₂ concentration of 3–6 mol %. In the two-phase region, the transport properties (conductivity and activation energy of conduction) only slightly depend on the dopant concentration.