Alkali and alkaline earth metals halides

Based on the concept of mixed-framework lattices, we have reported a novel class of hybrid solids that were discovered via salt-inclusion synthesis [4—7]. These new compounds exhibit composite frameworks of covalent and ionic lattices made of transition-metal oxides and alkali and alkaline-earth metal halides, respectively [4]. It has been demonstrated that the covalent frameworks can be tailored by changing the size and concentration of the incorporated salt. The interaction at the interface of these two chemically dissimilar lattices varies depending upon the relative strength of covalent vs. ionic interaction of the corresponding components. In some cases, the weak interaction facilitates an easy... 

Salt-inclusion solids described herein were synthesized at high temperature (>500°C) in the presence of reactive alkali and alkaline-earth metal halide salt media. For single crystal growth, an extra amount of molten salt is used, typically 3 5 times by weight of oxides. The reaction mixtures were placed in a carbon-coated silica ampoule, which was then sealed under vacuum. The reaction temperature was typically set at 100-150 °C above the melting point of employed salt. As shown in the schematic drawing in Fig. 16.2, the corresponding metal oxides were first dissolved conceivably via decomposition because of cor-... 

TABLE 1.16 Lattice energies of some alkali and alkaline earth metal halides at 0 K... 

OXOACIDITY SCALES FOR MELTS BASED ON ALKALI- AND ALKALINE-EARTH METAL HALIDES... 

Oxoacidity scales for melts based on alkali- and alkaline-earth metal halides 119... 

From the dependence shown in Fig. 3.7.15 it can be concluded that the growth of the parameter a of the cubic crystalline lattice of the oxide increases its solubility in ionic melts based on alkali- and alkaline-earth metal halides. This may be explained by the fact that the increase in the parameter a of the crystalline lattice results in the weakening of the interaction between ions and molecules in oxide crystals, which favours dissolution of these oxide crystals in molten salts. The solubilities of ZnO and PbO are not shown in Fig. 3.7.15, since at the temperature of the experiment both oxides possess hexagonal crystalline lattices. 

Mishchenko and co-workers ° and Krestov and Klopov have measured heats of solution for several alkali and alkaline earth metal halides and nitrates in water-methanol mixtures. The data, which are given only in graphical form, indicate the same functional dependence upon alcohol concentrations as those reported by Slansky, and Moss and Wolfenden. ... 

Scattered data for several other aprotic amides exist. Pistoia and Scrosati have reported the solubilities for several alkali and alkaline earth metal halides and transition metal halides in JV,JV-dimethylacet-amide. The solubilities increase in the order Cl < Br < I. Alexander and co-workers have reported solubility product values for numerous silver salts in DMA. They have also reported values for silver salts, KBr and NaCl in hexamethylphosphorotriamide (HMPT). The solubilities of the silver halides in both these solvents follow the same trend as they do in water. Coleman has measured the solubilities and activity coefficients of sodium and potassium chlorides in several dialkylamides containing water. Distribution coefficients of the salt between water and amide have also been calculated. 

TABLE 4.5 Lattice Energies of Some Alkali and Alkaline Earth Metal Halides at OK (kJ/mol) ... 

Molten salts may be classified (1) into simple ionic salts (e.g. the alkali and alkaline earth metal halides), simple and polymeric oxyanionic salts (e.g. metal nitrates, carbonates, phosphates. 

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