Cadmium stannate

The ammonium fluoride technique used by Raviendra and Sharma for ZnO (described earlier) has also been used by them to deposit cadmium stannate using a mixture of CdCli and SnCU [52]. After annealing at over 200°C, Cd2Sn04 was obtained. Optical and electrical properties of these films are described in Chapter 8. 

Cadmium stannate, used as electrodes in photogalvanic cells, is another example of a transparent conductor oxide (TCO) having desirable properties, such as good durability and chemical resistance. It can be produced by the spray pyrolysis CVD method with organic solutions of CdCH and SnCH or [Cd(hfa)2 (TMEDA)] and [Sn(acac)2]. ° It also shows the unexpected effect of improving transparency with increasing Him conductivity higher than tin-doped indium oxide. 

A large number of commercially important plating processes occur from complex ion baths in which the metal is a constituent of an anionic complex, e.g. copper, zinc, cadmium, silver and gold are all commonly plated from cyanide baths, and tin plates from a stannate bath in which [SnIV(OH)6]2 is present. Chromium is commonly plated from a chromate bath although in this case the background medium is acid rather than alkaline. Thus the mechanism of deposition of metals from anionic complexes is of particular interest. It will be instructive to comment on two situations, one occurring in alkaline baths, the other in acidic baths. 

Inorganic pigments are found in the earth. Iron and lead oxides provide earth colors. Copper calcium silicate and cobalt stannate provide blues. The colors burnt sienna and burnt umber come from iron oxides. Green pigments come from chromic oxide, calcinated cobalt, and zinc and aluminum oxides. Red pigments come from cadmium sulfide, cadmium selenide, and barium sulfate. All these chemical compounds come from the earth. 

Techniques to handle the aluminum so that it can be continuously fed as chips or pellets into the electrochemical system have also been developed." One design uses aluminum particles having diameters of 1 to 5 mm." The electrode is a pocket whose walls are composed of cadmium-plated expanded steel screen. The electrode is fed by a system which keeps the cell maintained with an aluminum particulate at an optimum level. Figure 38.32 shows the performance of a cell operating at 50°C using SN KOH-containing stannate. The battery, with an electrode area of 360 cm, was able to deliver a current of 56 A at 1.35 V for 110 h, with the automatic addition of aluminum every 20 min. 

---