Silver bromide conductivity

In this section we are concerned with the properties of intrinsic Schottky and Frenkel disorder in pure ionic conducting crystals and with the same systems doped with aliovalent cations. As already remarked in Section I, the properties of uni-univalent crystals, e.g. sodium choride and silver bromide which contain Schottky and cationic Frenkel disorder respectively, doped with divalent cation impurities are of particular interest. At low concentrations the impurity is incorporated substitutionally together with an additional cation vacancy to preserve electrical neutrality. At sufficiently low temperatures the concentration of intrinsic defects in a doped crystal is negligible compared with the concentration of added defects. We shall first mention briefly the theoretical methods used for such systems and then review the use of the cluster formalism. 

Silver(I) halide complexes of oA could not be prepared. The phosphine ap, however, reacts with silver iodide to give a colourless, unstable, non-conducting compound of empirical formula Agl(ap). This compound reacts with excess ap to give the stable 2 1 adduct Agl(ap)2- Silver bromide and silver chloride react directly with the ligand to give similar 2 1 adducts. These complexes are essentially monomeric, contain three-coordinate silver (I) and uncoordinated olefinic groups. The structure of the 1 1 adduct is unknown. 

With small dimensions of the forbidden band the electron transfer of the impurity or of the main substance to the conduction band may take place. The most important luminescent minerals of this kind are ZnS and silver bromides. With the interband spacing of 3-4 eV a UV irradiation with a wavelength of less than 300 nm has enough energy to detach electrons and transfer them from the filled valence band into an empty conduction... 

They reasoned that in the vicinity of a silver sulfide speck the conduction band is bent downward and photoelectrons could reach the surface of the crystal more easily, and hence more readily form surface image. However, the thickness of the silver sulfide layer in their experiments was about 4 pm, which far exceeds that of any sensitivity center on emulsion grains. The relevance of their observation to S-sensitization of emulsions is doubtful. Starbov (147) found no evidence of change in the surface potential when either the (111) or the (200) surface of an evaporated silver bromide layer was sulfur-sensitized. 

What we require is a place on the surface of the grain where the electron will "stick." If the conduction levels in silver sulfide are lower than in silver bromide, the sulfide speck will have just this effect an electron in the conduction level of the lattice, on meeting the sulfide speck, will fall down a potential hill and become stuck. 

Tubandt was a pioneer of - solid state electrochemistry. He introduced a methodology to determine the - transport numbers of ions in -> solid electrolytes [i], which is now referred to as -> Tubandt method. Together with his co-workers he performed seminal studies of conductivities and transport numbers of solid electrolytes, e.g., of silver, lead, and copper halides, and silver sulfide. He showed for the first time that the entire dark current of silver bromide is transported by silver ions, and also that slightly below the melting point silver iodide has a higher conductivity than the melt. 

The poorly characterized i(dddt)21 Ag,Brv product, which probably is a polymeric silver bromide containing species, behaves like a metal down to 4.3 K (167). The Pd analogue, [Pd(dddt)2]Ag1 54Br3 50, is metallic down to 1.3 K (169). Its crystal structure consists of layers of [Pd(dddt)2] moieties alternating with layers of silver bromide complex anions. A noticeable feature lies in the existence of a uniform stacking of Pd(dddt)2 in the conduction layers, instead of the stacking of dyads usually encountered in Pd complexes (9, 160, 175-177). Several other dddt Pd compounds exhibiting metal-like properties have been reported but poorly characterized (see Table III). 

After correcting for the conductivity of the solvent, the conductivity of a saturated solution of silver bromide in water is 6.99 x 10 S cm at 18°C. If the molar ionic conductivities of Ag" (aq) and Br (aq) are 53.5 and 68.0 S cm mol respectively, find the solubility of silver bromide in water. From this calculate the solubility product for silver bromide. 

In the actual experiment, size-selected silver ions are softly landed on a transparent conductive glass plate covered with fine grains of silver bromide with a diameter of about 1 fan the cluster ions are rapidly neutralized to... 

This approach has been confirmed by experimental results. For example, it has been found that ionic compounds, hitherto regarded as dielectrics, can behave — under certain conditions - as typical semiconductors. Thus, the low-temperature mobility of electrons in silver bromide and chloride can reach a few thousand cgs units (cm V sec ) [5]. The success achieved in investigations of organic semiconductors (such as the observation of n-type conduction in low-molecular organic materials) have added additional members to the semicon-... 

Silver bromide is a semiconductor. Absorbed light excites electrons in the conduction band and electron holes in the valence band. The holes oxidize bromide ions to traces of bromine that are dissolved in the gelatine layer. The free electrons reduce silver ions to silver atoms that form the catalytically active clusters in the halide crystallites. The reactions are ... 

R. J. Friauf [1954] Polarization Effects in the Ionic Conductivity of Silver Bromide, J. Chem. Phys. 22, 1329-1338. 

Raleigh [25] also studied the potentiostatic transient response of cells of type V. Under these conditions, Eq. (7) applies. Silver bromide equilibrated with gaseous bromine conducts electronically via electron holes [26]. Under these conditions, the activity of silver at the blocking electrode is. 

Matejec ( ) has measured the DC conductance of thin silver bromide single crystals in contact with aqueous solutions of various silver ion concentrations. He found that the conductance of the crystals varied with the silver ion concentration and concluded the applicability of the Grimley-... 

The determination of iodide with ion-selective electrodes is possible with commercial sensors often based on ion conducting Ag2S—Agl solid membranes [57]. A PVC membrane-based sensor employing a silver complex with thiourea derivatives has been reported by El Aamrani et al. [202]. Interference from thiocyanate and bromide was investigated and a limit of detection in the nanomolar range was determined. A study assessing the performance... 

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