The formation of crystalline LiNbO3 (LN) from LN glass has been studied by means of differential scanning calorimetry and in situ synchrotron X-ray diffraction. The LN glass with no glass former was prepared by the polymerized complex method. The isothermal kinetics of the crystallization process is described using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation and the Avrami exponent n is found to be ~2.0, indicating that the crystallization mechanism is diffusion-controlled growth with a decreasing nucleation rate. The effective activation energy of crystallization calculated from isothermal measurements is 6.51 eV. It is found that the LN glass directly transforms into a rhombohedral LN crystal without any intermediate crystalline phase and most crystal grains are confined within the size of ~40 nm irrespective of different isothermal temperatures. Application of JMAK theory to the non-isothermal thermoanalytical study of crystallization of LN glass is discussed.
The authors investigated the effect of external Qi-therapy (EQT) on changes in encephalograms (EEGs) and circulating cortisol concentrations. Ten college students participated in crossover sessions, receiving EQT or placebo treatment with their eyes open. Subjects reported improved emotions of satisfaction, relaxation, and calmness during EQT as compared to levels reported during placebo treatments. There were significant differences in the proportions of alpha and beta EEG waves between the two sessions, and the relative strengths of alpha waves were higher during EQT than during control sessions (p < .05). Plasma cortisol concentrations during EQT were significantly lower than during control sessions p < .05). Thus, Qi-therapy was more effective in inducing relaxation than placebo treatment.
Ionic conductivities in the bismuth germanate silicate (BGSO) glasses have been investigated in the frequency range 100 Hz to 15 MHz and in the temperature range from 300 K to above the glass transition temperature T g . The frequency-dependent electrical data have been discussed in the framework of the complex impedance and the power-law conductivity. The electrical conductivity is strongly composition dependent and it follows the Arrhenius relation in the experimental temperature range. The activation energies of dc and ac conductivities obtained by the power-law analysis show that the BGSO glasses satisfy the Barton, Nakajima, and Namikawa (BNN) relation. The temperature-dependent interaction of conducting ions is discussed.
We have investigated Li effects on the structural property change in Li x Ni 0.5 Mn 1.5 O 4 (LNMO, x = 1, 0.7, 0.5, 0.3, 0.1, 0) by using Rietveld refinement with neutron diffraction measurements. The polycrystalline LNMO samples were synthesized using the sol−gel process and were calcinated at 1000 °C for 10 h. It was found that all the structures of LNMO belong to the face-centered cubic spinel structure Fd3̅ m, irrespective of Li amount, and that there exists a small amount of the NiO secondary phase for x = 1. As lithium is extracted from LNMO, oxygen reduction also follows, and the amount of oxygen released (y) from the sample changes in the manner to keep both the amount and the oxidation state of Ni/Mn cations; the total chemical formula can be written as (Li x ) x+ (Ni 0.5 Mn 1.5 ) 6.25+ (O 4−y ) −(6.25+x) for x ≤ 0.7 and LiNi 0.5−δ Mn 1.5 O 4−y−δ + δNiO with δ = 0.012 for x = 1. Both the lattice constant of a unit cell and the nearest neighbor bond distances of ions in LNMO continuously decrease with the increase of Li content, indicating that the variation of those parameters are much dependent on the strength of coulomb interactions between ions.
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