SmecticBliquid-crystalline glass (at 77 °K) as seen by the Mössbauer effect of Sn-bearing solute molecules

Explosive crystallization of amorphous substances

“…Одна из актуальных перспектив таких исследований -дать последователь-ную, по возможности количественную интерпретацию особенностей термо-грамм, получаемых в экспериментах по дифференциальному термическому анализу аморфных веществ 108 . Обратим внимание еще на то, что неизотермические эффекты, аналогичные ВК в стеклах, могут, по-видимому, наблюдаться при распаде структурно замороженных метастабильных фаз в других объектах (например, в жидких кристаллах 112 , полимерах пз ), а ряд теоретических результатов для дву-мерного и трехмерного теплоотвода может оказаться полезным при иссле-довании качественно аналогичных явлений «безгазового» горения конденси-рованных веществ в приближении узкой зоны реакции *» 2 . Авторы глубоко признательны покойному Я. Б. Зельдовичу за интерес к работе и ряд полезных советов по написанию данного обзора.…”

Glass Transition Dynamics and Crystallization Kinetics in the Smectic Liquid Crystal 4-n-Butyloxybenzylidene-4′-n′-octylaniline (BBOA)

“…5 Although the vitrification of crystal-like smectic phases, in which molecules are arranged within the layers (smectic B, E, F, G, H, etc. ), 6−11 is not evident, a few examples of the glasses of smectic phases have been reported: the glass of smectic B in 4-n-butyloxybenzylidene-4′-n′octylaniline (BBOA), 12 the glass of smectic H, 13 the glass of smectic E, 14,15 and the glass of smectic G. 16,17 Contrary to "conventional" glasses considered as amorphous materials, the glassy state of the crystal-like phase is characterized by orientational disorder of the molecules, which otherwise possess translational order. In previous work, we showed that in the vitreous state of the SmE phase, the smectic layers are preserved, but the translational order of molecules within the layers is slightly disturbed.…”

“…Upon slow cooling, an additional phase transition from the SmB hex to the SmB Cr phase is observed at 287 K, which corresponds to a change in the type of stacking sequences of molecular layers. On the basis of Mossbauer spectroscopy, Uhrich et al 12,13 found that the SmB Cr phase vitrifies at 175 K. The molecular motions of BBOA in smectic phases were studied by NMR and quasielastic neutron scattering. 20,21 In this article, we report a detailed study of molecular dynamics of BBOA molecules in various equilibrium phases, in the glass transition region as well as during crystallization, by means of broadband dielectric spectroscopy (BDS).…”

“…Real part ε′(T) and imaginary part ε″(T) of the complex dielectric permittivity of BBOA at ν = 3.4 Hz measured on fast cooling (open symbols) and on subsequent slow heating (solid symbols). The vertical dashed lines mark the glass transition temperature, T g = 175 K, determined by Mossbauer spectroscopy 12,13. Other discernible phase transition temperatures are T CrB = 225 K, T CrA = 250 K, and T Cr = 270 K.…”

Energy band gap, intrinsic carrier concentration, and Fermi level of CdTe bulk crystal between 304 and 1067K

“…[3][4][5][6][7][8][9][10][11] For most of these analyses, the high temperature equilibrium between electron n and hole p was adopted by either ͑1͒ using an expression for the intrinsic carrier concentration 10,11 in the form typical for a nondegenerate semiconductor with parabolic conduction and valence bands, n i / T 3/2 = K 0 exp͑−H / kT͒ or ͑2͒ using a quasichemical reaction constant, [3][4][5][6][7][8][9] such as np = K = K 0 exp͑−H / kT͒, where K 0 and H are the adjustable parameters. However, the electro-optic properties of CdTe vary tremendously among crystals and are strongly influenced by the physics and chemistry of the materials during its growth process at elevated temperatures.…”