Transition, crystallographic

Laf+(Cu2xCuf t2x)04 x. The crystallographic transition temperature for this oxygen-deficient material now occurred at a higher temperature, 263°C. 

Bertaut, E. E (1988) Eulers indicatrix and crystallographic transitive symmetry operations in the hyperspaces E ri). Comptes Rendus de VAcademic des Sciences, Serie II (Mecanique, Physique, Chimie, Sciences de I Univers, Sciences de la Terre). 307(10) 1141-46. (The author uses elementary number theory in this article on crystallographic symmetry operations.)... 

It should be noted that Young, Udaja, and Trimm found that presence of a metal (in their case Ni) may promote the crystallographic transition and sintering of the support (in this case gamma to alpha alumina). This warns us that the morphological transitions for mixed phases may take place luider different conditions than found for the phases separately. 

It is for this reason that the twin boundaries must be mobile. In effect, the size of the individual twins increases, and the number of twins decreases. Above Af the structure returns to the high-tempera-ture form, which is untwined and no longer deformed (Figure 8.17), which is why the crystallographic transition must be reversible. The material has remembered its original shape. 

Tj is a crystallographic transition temperature eonnected to change of valence. 

The crystallographic transition at the Curie temperature is first order with the values given in Table 116 being obtained for the enthalpy of transition ... 

The stractural and magnetic properties of the whole series of Heusler type compoimds i Au2ln R = Y, La-Lu) has been investigated with great care by Besnus et al. (1985,1986). The indides with lanthanum, cerium, praseodymium, and neodymium show a crystallographic transition from cubic to tetragonal as is evident from X-ray powder data. The transition temperature decreases from 355 K for LaAu2ln to 70 K for the neodymium compound. This... 

The crystallographic transitions which occur in the Ce below room temperature are discussed in ch. 4 section 2.2. Yb has been observed to transform on cooling from its room temperature fee form to an hep structure at 270 K by Kayser (1970). The transformation occurs martensitically with an M, temperature of... 

Table 4. Site occnpancy and crystallographic transition temperatnres. a) Distribntion of A1 ions in mordenites [97A1].

The phase transformations described above have been first-order transformations with measurable enthalpies. Second-order transformations, however, only exhibit a change in heat capacity at the transformation. Examples are many magnetic transitions, the glass transition in polymers, and some crystallographic transitions... 

The discussion of DTA in the previous section describes the precautions and recommended practices for calculating the melting point from DTA or DSC curves. The advent of instrumentation for simultaneous DTA/TG or DTA/EGA allows the TG and EGA instruments to be calibrated directly as well. Many secondary standards for temperature measurements have also been developed for thermal analysis. These have been based on solidj—solid2 crystallographic transitions or magnetic transitions, that is, Curie or Neel temperatures. 

FeS sc 360-"50 Farad crystallographic transition temperature 7i 428 K spin-flop transition at T=463 K 73T1, Fig. 134, 135... 

Structural phase transitions that occur during lithiation are typically undesirable since they often lead to slow kinetics and poor cycle life. In that respect, the electrochemically driven amorphization of silicon is advantageous since it allows lithiation to occur while b3q)assing multiple crystallographic transitions. However, the electrochemical properties of silicon and germanium could likety... 

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