Copper ionic conductivity

In spite of the extraordinarily high ionic conductivity of silver- and copper-ion conductors, these materials suffer from their low capacity and energy density. In addition, only a few positive electrode materials have been found until now. 

The ionic conductivity is much higher than in the corresponding copper halides (see Fig. 5). At temperatures above 250°C, they enter the region of optimized ionic conductors (150). 

Cul) is not due to point defects but to partial occupation of crystallographic sites. The defective structure is sometimes called structural disorder to distinguish it from point defects. There are a large number of vacant sites for the cations to move into. Thus, ionic conductivity is enabled without use of aliovalent dopants. A common feature of both compounds is that they are composed of extremely polarizable ions. This means that the electron cloud surrounding the ions is easily distorted. This makes the passage of a cation past an anion easier. Due to their high ionic conductivity, silver and copper ion conductors can be used as solid electrolytes in solid-state batteries. 

Electrolytes are used in electrochemistry to ensure the current passage in -> electrochemical cells. In many cases the electrolyte itself is -> electroactive, e.g., in copper refining, the copper(II) sulfate solution provides the ionic conductivity and the copper(II) ions are reduced at the - cathode simultaneous to a copper dissolution at the - anode. In other cases of -> electrosynthesis or - electroanalysis, or in case of - sensors, electrolytes have to be added or interfaces between the electrodes, as, e.g., in case of the -> Lambda probe, a high-temperature solid electrolyte. 

In this paper. We report the hydrothermal synthesis, structural characterization and ionic conductivity of a novel hydrated copper bismuth vanadate, Cu2Bi4V20i3 3H20 and its high temperature phase. 

The phenomenon of bond isomerism depending on the state of aggregation, like that of direct bond isomerism, is not restricted to halides of P, As, and Sb. Anhydrous nitric acid, for example, shows appreciable ionic conductivity in the liquid state, but the vapor consists of molecules (1,125). Well-defined salts such as Cu[N03]2 may also be mentioned in this connection. The vapor of copper(II) nitrate contains molecules (5). The concept of isomerism is used here in a broad sense, as the example of anhydrous nitric acid shows. Whereas classical isomerism is restricted to two molecules of the same composition, the phenomenon under discussion here relates to the system as a whole. Liquid HNO3 may also be thought of as a solution containing an ionic form dissolved in the anhydrous acid, which functions as the solvent. This relation is involved in the next type of bond isomerism to be discussed, where the solvent plays a part. 

If the ionic conductivity is low but no longer negligible (roughly, the part of electronic conductivity is more than 0.5), the cathode deposit should consist of two layers a thick outer one including LVls and a thin inner one including pure metal. Such situation can be observed when some species are added to the bath increasing the electronic conductivity of the film, as it happens when copper compounds are added to the electrolyte for silicon deposition [6]. 

Firstly, the figure of merit for an electrolyte is the conductance rather than the conductivity. Very useful polymer electrolytes have been developed for which the conductivity is 10" S cm" which is derisory in comparison with values of room temperature ionic conductivity that approach 1 Scm" both for typical dilute aqueous or non-aqueous electrolyte solutions and for optimized silver or copper-based solid electrolytes such as Rb4Cui6l7-x CI13-X [112, 113]. This is because polymer electrolytes are mechanically adequate to maintain a high-integrity barrier when sandwiched between anode and cathode, even when the electrolyte thickness is only 10-100 pm, corresponding to an electrolyte resistance of 1-10 Q. 

The data shown in Fig. 6 represent values of the conductivities of CuCl coexisting with copper. However, the electronic and ionic conductivities may both depend on the stoichiometry fixed by the chemical potentials of the constituents. Shown in Fig. 7 are two schematic graphs [18] for the behavior of CaF2 The upper graph shows the isothermal variation of the defect concentration with partial pressure of fluorine (a Brouwer or Kroger-Vink diagram) and the lower one shows the corresponding behavior of the conductivities. 

RbAg I is remarkable in that the a iodide phase, with its associated nigh ionic conductivity, extends down to room temperature. In principle RbAg I disproportionates below 27 C to Rb Agl and Agl, but this reaction is so slow that, in practice, the conductive compound may be employed as an electrolyte in a dry atmosphere at room temperature. The MAg I structure exists with M = K, Rb or NH. Analogous bromides do not exist. The copper halide KCu I is reported stable over a narrow temperature range (257-332 CJ(l7). 

Toda K, Kameo Y, Kurita S, Sato M (1996) Crystal structure determination and ionic conductivity of layered perovskite compounds NaLnTiO (Ln = Rare Earth). J Alloys Compd 234 19-25 Tomchenko AA, Harmer GP, Marquis BT, AUen JW (2003) Semiconducting metal oxide sensor array for the selective detection of combustion gases. Sens Actuators B 93 126-134 Tongpool R, Leach C, Freer R (2000) Temperature and microstructural dependence of the sensitivity of heterocontacts between zinc oxide and copper oxide in reducing environments. 1 Mater Sci Lett 19 119-121 Traqueia LSM, Marques FMB, Kharton VV (2006) Oxygen ion conduction in oxide materials selected examples and basic mechanisms. Bol Soc Esp Ceram 45(3) 115-121... 

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