Selenates binary

Thousands of compounds of the actinide elements have been prepared, and the properties of some of the important binary compounds are summarized in Table 8 (13,17,18,22). The binary compounds with carbon, boron, nitrogen, siUcon, and sulfur are not included these are of interest, however, because of their stabiUty at high temperatures. A large number of ternary compounds, including numerous oxyhaUdes, and more compHcated compounds have been synthesized and characterized. These include many intermediate (nonstoichiometric) oxides, and besides the nitrates, sulfates, peroxides, and carbonates, compounds such as phosphates, arsenates, cyanides, cyanates, thiocyanates, selenocyanates, sulfites, selenates, selenites, teUurates, tellurites, selenides, and teUurides. 

A quantitative analysis of the kinetics of CdSe deposition from selenosulfate, Cd(II)-EDTA baths in terms of a mechanism involving nucleation and electrode kinetics has been given by Kutzmutz et al. [65], Note also that selenosulfate-containing baths have been used for the anodic selenization of vacuum-deposited metal films in order to synthesize CdSe and other binary selenide semiconductor thin films such as CuSe and InSe [66],... 

Binary Selenides. Most binary selenides are formed by heating selenium in the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts in aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH Se [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the tellurides. Selenides of the alkali, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are insoluble in water. Polyselenides form when selenium reacts with alkali metals dissolved in liquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

The type n isotherms describe the concentration dependence of conductivity for binary systems containing only one conductive component. In this case also, two geometric subtypes may be distinguished. Subtype 11a - has monotonically convex shape (i.e., without extreme) in the direction of flic composition axis. The binary system, selenic acid-acetic acid, can serve as an example of this kind of dependeney. Subtype 11b includes isotherms wifli a maximum (minimum) - most widespread kind of isotherms (for example perchloric... 

Binary rare earth selenates 5.2.1. Preparation and structures... 

Beginning in the late 1960 s, Giolito and Giesbrecht with coworkers imdertook a systematic study of the formation and properties of binary and ternary selenates of the rare earths. They have mainly used thermoanalytical and IR spectroscopic methods to characterize the solid compoimds. At about the same time singlecrystal X-ray diffraction data have become available from other laboratories. Extensive thermoanalytical studies have, also been carried out by Nabar and CO workers. 

Consequently, we will start with the description of oxo-selenates(VI) in the first part of this chapter, and then move on to the major part of the article which is dedicated to oxo-selenates(lV). The oxo-selenate(Vl) section provides the description of various binary compounds in the first part (section 2.1), and will discuss the respective ternary phases in the second part (section 2.2). Among the properties of oxo-selenates(VI) (section 2.3), the thermal behavioitr firms out to the best irrvestigated one. The oxo-selenate(IV) section also starts with the binary species (section 3.1). These are the best investigated oxo-selenates so far, so that more details can be given, for example on synthesis (section 3.1.1) of the R2(Se03)3 type compoimds (section 3.1.2) which are completely known. Subsequent sections are devoted to the anionic (section 3.2) and cationic (section 3.3) derivatives of oxo-selenates(IV) and finally, properties of oxo-selenates(lV) will be discussed. The last section summarizes orrr present knowledge of mixed-valent oxo-selenates(IVA ) which, unfortunately, remairts limited. 

Synthetic routes to the binary rare earth oxo-selenates(IV) R2(Se03)j... 

As anionic derivatives of selenates(IV), those compounds shall be considered in which some of the selenite (or diselenite) anions are replaced by halide ions (section 3.2.2) or even by complex anions (section 3.2.3). In a strict sense, the oxide-selenites mentioned in section 3.1 are anionic derivatives of selenates(lV) with SeOj groups replaced by oxide ions. However, they belong to the binary system R203/Se02 and that s why they were discussed in that context and not within this section. On the other hand, the oxide-halides will be discussed here because they are members of the ternary systems R203/RX3/Se02 (see section 3.2.2). 

---