Neodymium vapor pressure, high temperature

Vapor Phase Formation and Condensation In order to grow whiskers by vapor phase formation and condensation, the bulk SiC is first vaporized by heating to very high temperatures (>2200 °C), usually under reduced pressure. Upon cooling, a-SiC whiskers form on the nucleation sites. The addition of lanthanum, yttrium, neodymium, or zirconium leads to an increase in the growth rates. However, whiskers are no longer produced commercially using this sublimation process. 

The shape of the curve shown in Figure 56 predicts a fairly high stability of neodymium and promethium dichlorides among the compounds with CN = 9 and dysprosium and thulium dichlorides among the compounds with CN = 7, that is, exactly those lanthanide dichlorides that (except PmCl2) not only were successfully synthesized but also were the subject of some physicochemical measurements that required heating to high temperatures. For instance, saturated vapor pressure of... 

Oxides. Decomposition pressure measurements on the TbO system by Eyring and his collaborators (64) have been supplemented by similar and related studies on the PrO system (46) and on other lanthanide-oxygen systems (43, 44). Extensive and systematic studies of vaporization processes in lanthanide-oxide systems have been undertaken by White, et al. (6, 188,196) using conventional Knudsen effusion measurements of the rates of vaporization of the oxides into high vacuum. Combination of these data with information on the entropies and Gibbs energy functions of reactants and products of the reaction yields enthalpies of reaction. In favorable instances i.e., if spectroscopic data on the gaseous species are available), the enthalpies of formation and the stabilities of previously undetermined individual species are also derived. The rates of vaporization of 17 lanthanide-oxide systems (196) and the vaporization of lanthanum, neodymium, and yttrium oxides at temperatures between 22° and 2700°K. have been reported (188). 

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