Neutron diffraction studies temperature dependence

The temperature dependence of the resistivity of Li WOs is shown in Figure 4. For x = 0.28, the anomalous peak was very large and occurred at about 600° K. for x = 0.34 the peak was much smaller and occurred at about 300° K. With increasing lithium concentration, therefore, the peak diminished in size and shifted to lower temperatures. The peak was completely reproducible and x-ray diffraction patterns showed that the cubic crystal structure existed both below and above the temperature at which the peak occurred. However, preliminary thermal analysis measurements indicated some sort of phase change. Mackintosh (6) has suggested the possibility of ordering of the lithium atoms, and neutron diffraction studies of these cubic Lia.WOs crystals should be made below and above the transition temperature. 

On lowering the temperature the conductivity passes through a maximum and then follows a complicated temperature dependence. The first partial derivative of In ct with respect to 1/ T has a maximum at 100 K, corresponding to the partial 3D ordering temperature, Tsd, found from neutron diffraction studies. At low temperature the behaviour is that of a semiconductor with a well-defined band gap. Studies at microwave frequencies have shown that the conductivity is frequency dependent below Studies under pressure indicate that T o increases and Tp... 

C. W. Garland C.F. Yamell (1966). J. Chem. Phys., 44, 1112-1120. Temperature and pressure dependence of the elastic constants of ammonium bromide, (table 5). R.S. Seymour A.W. Pryor (1970). Acta Ciyst, B 26, 1487-1491. Neutron diffraction study of NH,Br andNH, . 

Neutron diffraction studies carried out by Wilkinson et al. (1961) on an annealed and a cold worked sample support the observations of Koch and McHargue. Furthermore, they (K and McH) note that the temperature is higher than the As and At temperatures, which is unusual (for a typical martensitic transformation Af> As> Ma> Ms> Mf). The pressure dependence of this transformation (fig. 4.3) is based on the results of Gschneidner et al. (1962). 

Berastegui, P., Eriksson, S.G., and Hull, S. (1999) A neutron diffraction study of the temperature dependence of Ca2Fe20s. Mater. Res. Bull, 34, 304-314. 

Neutron diffraction studies on polycrystalline EuSe down to 2.1 K exhibited antiferromagnetic EuSe only, Pickart, Alperin [17]. However, early initial susceptibility data of nearly spherical crystals down to 1.6 K by Schwob, Vogt [18] and the temperature dependence of the absorption edge indicated the existence of ferrimagnetic EuSe below 2.8 K, Busch [19] (the temperature of 3.8 K was reported by [18]). 

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