Group metal silicides

Silicon-containing ceramics include the oxide materials, silica and the silicates the binary compounds of silicon with non-metals, principally silicon carbide and silicon nitride silicon oxynitride and the sialons main group and transition metal silicides, and, finally, elemental silicon itself. There is a vigorous research activity throughout the world on the preparation of all of these classes of solid silicon compounds by the newer preparative techniques. In this report, we will focus on silicon carbide and silicon nitride. 

Infrared laser diodes -platinum silicide detector [PLATINUM-GROUP METALS, COMPOUNDS] (Vol 19) -role m printing processes [PRINTING PROCESSES] (Vol 20)... 

Transition-, Inner-Transition, Group-IB and -MB Metal Silicides 5.10.3.2.1. Transition-Metal Silicides... 

Other five Co atoms has one, and there are eight bridging CO groups. The coordination number 10 is found in the structures of several transition metal silicides and in decamethylsilicocene... 

The present status of information about phase equilibria and formation of ternary metal silicides with R elements (R = Sc, Y, and the lanthanides) is summarized in fig. 1. Phase equilibria have been investigated for only a small number of the possible ternary combinations R-M-Si, and for a larger number of ternary systems only a few compounds have been identified to date. Little information is available involving main group elements. 

A metal silicide is a compoimd that has silicon with more electropositive metal elements. Metal silicides have been the subject of numerous studies because of their potential applications in Si-based microelectronics and optoelectronics. They can be classified into two groups metallic and semiconducting silicides. Some metallic silicides (VsSi, NbaSi, CoSi2, etc.) are superconductors. Table 4.1 summarizes some physical properties of metallic silicides. 

Silicon (3), which resembles metals in its chemical behavior, generally has a valence of +4. In a few compounds it exhibits a +2 valence, and in silicides it exists as a negative ion and largely violates the normal valency rules. Silicon, carbon, germanium, tin, and lead comprise the Group 14 (IVA) elements. Silicon and carbon form the carbide, SiC (see Carbides). Silicon and germanium are isomorphous and thus mutually soluble in all proportions. Neither tin nor lead reacts with silicon. Molten silicon is immiscible in both molten tin and molten lead. 

In addition to the types of compounds discussed so far, the group IVA elements also form several other interesting compounds. Silicon has enough nonmetallic character that it reacts with many metals to form binary silicides. Some of these compounds can be considered as alloys of silicon and the metal that result in formulas such as Mo3Si and TiSi2. The presence of Si22 ions is indicated by a Si-Si distance that is virtually identical to that found in the element, which has the diamond structure. Calcium carbide contains the C22-, so it is an acetylide that is analogous to the silicon compounds. 

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