Regularity of changing of the thermochemical characteristics of lead-rich intermetallides in lead - lanthanide systems

System analysis of thermochemical characteristics, viz. temperature and enthalpy of melting of intermetallides (IM) of lead-rich Pb-Ln systems, Pb3Ln, Pb2Ln and Pb4Ln3 compositions was carried out. It is shown the incomplete or lacking information about these characteristics for the IM of the whole series of lanthanides. The Poluektov semiempirical method was used as the main method for determining and/or refining of the thermochemical characteristics of IM. The method takes into account the influence of the number of 4f electrons, spins and orbital moments of motion in the lanthanide atoms, and the temperature and enthalpy of melting of the intermetallides of the indicated compositions are determined and/or refined. By Kireeva and Karapetyants semiempirical methods of difference, information for lanthanum IM, gadolinium and lutetium, that missed in the literature is determined and/or refined. The data for the IM of these lanthanides are basic for calculation by the basic method. Certain values of the melting temperature of IM allowed to calculate the enthalpy of melting of IM by the well-known formula. The most complete information on the temperature and enthalpy of melting of the IM compositions Pb3Ln, Pb2Ln and Pb4Ln3 allowed us to establish that the regularities of changes in these characteristics of IM are depending on the nature of the lanthanides. These regularities have complex nature with the manifestation of the “notebook-effect”, and are clearly divided into the corresponding subgroups, cerium and yttrium. These regularities within the subgroups of the lanthanide manifest themselves differently, depending on the nature of the lanthanides and those factors that are taken into account in processing of the data by the basic semiempirical method. The properties of europium and ytterbium IM fall out from the general regularity, due to the filling of their 4f orbitals with electrons half or completely. In general, as the number of lanthanides increases, the temperature and melting enthalpy increase in a series of similar IM compositions of Pb4Ln3 and decrease in these characteristics for the Pb3Ln and Pb2Ln compositions are observed.