Specific heat intermetallics

FIGURE 13 Volumetric specific heat of two rare-earth intermetallic compounds and lead. 

Much attention was paid to slruelures, superconducting properties, magnetic susceptibilities, Knight shifts, and specific heats of intermetallic compounds of technetium. Their structure types and lattice constants arc presented in Table 9.3. A. 

The crystal chemistry of the YbTX compounds and the various physical properties and spectroscopic data (magnetism, electrical conductivity, specific heat, Ljn spectra, Mdssbauer spectroscopy) are critically reviewed in the present article. Additionally we comment on the synthesis conditions and the chemical bonding within the YbTX compounds. We have written this article from the viewpoint of a solid-state chemist who is interested in the interdisciplinary field of inorganic and physical chemistry, elucidating structure-property relations of intermetallic compounds. 

In the present section we focus on the various chemical and physical properties of the equiatomic YbTX compounds especially the physical properties, which have been intensively investigated in the last two decades. Besides detailed magnetic susceptibility and electrical resistivity measurements, various other techniques have been used to get deeper insight into the peculiar properties of these intermetallics " Sn and °Yb Mdssbauer spectroscopy, specific-heat data, thermopower measurements, solid-state NMR, photoemission studies, neutron dif action, muon spin relaxation, and a variety of high-pressure experiments. The diverse data are summarized in the following subsections. 

Deformation potential coupling constants are of the order of fip, (Ziman 1960). To observe deformation potential effects in the temperature dependence of elastic constants several conditions have to be met as discussed above dpA(,(0) must be large and - Eq has to be of the order of k T. This excludes normal metals and only d-band metals with rather narrow bands can exhibit this behavior. Typical examples have been given above. In intermetallic rare-earth compounds simple density of states arguments show why elastic constant effects can be observed only for CsCl-type and Th3P4-type materials. In table 4 electronic specific heat values are listed for various rare earth compounds. This is an updated list of a previous work, see Liithi et al. (1982). This table indicates that monopnictides and monochalcogenides have smaller values of y than CsCl- and Th3P4-structure materials, i.e., the 5d band of the former structure is more hybridized than in the latter. 

In this section we describe how the specific heat, magnetic susceptibility and electrical resistivity of anomalous lanthanide and actinide intermetallics respond to applied pressure. Generally each subsection is organized by material type first Ce-based compounds, then those based on Yb and finally U-based systems. Only in the last subsection on semiconductors are these systematics broken. Although on occasions we digress into a brief discussion of the experimental observations, ihe bulk of critical discussion related to data presented here and in sect. 3 is reserved for sect. 4. 

The negative Griineisen parameters found from specific heat and susceptibility measurements on anomalous Yb intermetallics are consistent with the pressure-induced resistive response of these materials as well. For pressures less than 16kbar, the... 

The specific heat y of some metals and intermetallic compounds. 

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