Dysprosium heat capacity

Lanthanide (III) Oxides. The lanthanide(III) oxides will be used to illustrate the present breadth of our most extensive knowledge of the chemical thermodynamics of lanthanide compounds. Cryogenic heat capacities of hexagonal (III) lanthanum, neodymium, and samarium oxides, together with those of cubic (III) oxides of gadolinium, dysprosium, holmium, erbium, and ytterbium, have been reported (90, 91, 195). In addition, those of thulium, lutetium, and a composition approaching that of cerium (III) oxide have also been determined, and five well-characterized compositions between PrOi.714 and PrOi.833 are currently under study (J93). 

Due mainly to impurity oxide, the low temperature heat capacity of dysprosium is strongly sample dependent, especially between about 0.5 and 0.8 K (see fig. 1 of Flotow and Osborne 1964). Thus any analysis based on this temperature range alone cannot be relied upon. The only safe criterion is that the purest samples presumably give the lowest heat capacity from which we can obtain an upper limit for y and d(0). On this basis y 9.0 nJ/mole K for Dy. To obtain any further information from the experimental results, some assumptions must be made about Ce and Cl- Single crystal elastic constant data for Dy (Palmer 1970) give d(0)= 183 K as against polycrystalline results (Rosen 1968) where d(4.2) = 178 K. Flotow and Osborne (1%3) assumed Ce = 10.5 T mJ/mole-K and du(0) = 186 K and found a fit to Cooper s (1962) expression, eq. (5.7), with EJka 50 K. Lounasmaa and Sundstrdm (1966), on the other hand, using Ce+Cl= Cp(Lu) proposed the behaviour Cm= 107 T exp( —31/T) mJ/moIe-K. 

In the light of the recent work on Y, Gd, Tb, Ho, and Lu, described in the appropriate sections of this chapter, it is likely that none of these analyses represents the final picture for dysprosium. We must await further heat capacity work on high purity samples. 

Distillation, azeotropes, 6-177 to 195 Divergence, definition, A-68 to 74 DSC, definition, 12-1 to 4 DTA, definition, 12-1 to 4 Dubnium (element 105), 4-1 to 42,11-56 to 253 Dysprosium see also Elements electrical resistivity, 12-39 to 40 electron configuration, 1-18 to 19 heat capacity, 4-135 history, occurrence, uses, 4-1 to 42 ionization energy, 10-203 to 205 isotopes and their properties, 11-56 to 253 magnetic susceptibility, 4-142 to 147 molten, density, 4-139 to 141... 

As in the case of heat capacity, anomalies can also occur in the thermal expansivity of materials. Various transformations that occur in the solid state can alter the interatomic forces of the material and lead to changes in its overall dimensions. For example, the ferromagnetic Curie point of dysprosium at low temperatures leads to an irregularity in the expansivity. Other examples are KH2PO4 with a ferro-electric Curie point at 122 K, and the glass transitions of soft rubbers. In fact, the measurement of thermal expansion is a useful method by which solid-state transitions can be investigated. Table 3.8 gives values of thermal expansion for some structural materials at low temperatures. 

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