Concentration Of Ce Ions Research Articles

Effect of temperature in cerium-ion-catalyzed bromate-driven oscillators

The influence of substrate composition and initial reagent concentrations on activation energies in closed Ce-ion catalyzed Belousov-Zhabotinsky (BZ) reactions is reported. While changes in the initial concentration of organic substrate, bromate ion or sulfuric acid showed different changes in activation energies for the various organic substrate BZ systems, for all systems it was found that lowering the Ce-ion concentration leads to a significant decrease in the overall activation energy of the oscillator. When comparing the performance of a malonic acid oscillator run in a batch or in a continuous stirred flow reactor (CSTR), it was found that under CSTR conditions Q 10 values may become as low as 1.3, while for the batch system the corresponding Q 10 values are about 2.3.

ESR and electrical conductivity studies of (TeO 2) 0.95(CeO 2) 0.05 semiconducting glasses

Electron spin resonance (ESR) and d.c. conductivity measurements have been made on a prepared binary tellurite glass in the temperature range 200–400 K. The d.c. conductivity was found to be temperature dependent and had two regimes. The data were consistent with the small polaron transport mechanism and the polaron activation energy was 0.22 eV. The ESR spectra at high temperatures were characterized by two overlapping lines, a broad line with g = 2.00 and a narrow line with g = 1.967. At temperatures lower than 258 K, the narrow line disappeared and the broad line remained. This suggests that carriers become localized at T < 258 K. At T > 273 K, the conductivity arises from hopping of carriers between cerium sites. It was also found that the reduced valency ratio C (i.e., the ratio of the concentration of Ce 4+ ions to the total Ce ion concentration in the glass) increases with temperature.

Effects of disorder on the formation of coherence in a heavy-fermion alloy

We study the formation of the coherent state by investigating the density of states of a heavy-fermion alloy as a function of the concentration of Ce-ions. For simplicity, we consider an orbitally nondegenerate f-band hybridized with one conduction band in one dimension. The high correlations among the f electrons on the Ce-sites are introduced by excluding the double occupation of the f level by means of slave bosons treated within the mean-field approximation. The local densities of states are obtained for several concentrations by solving the one-dimensional mean-field slave-boson alloy problem exactly using a decimation technique.

Heavy-fermion behavior and the single-ion Kondo model.

Measurements of the temperature and concentration dependence of the specific heat, magnetic susceptibility, and electrical resistivity for ${\mathrm{Ce}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{La}}_{\mathrm{x}}$${\mathrm{Pb}}_{3}$ are presented. The data scale with the concentration of Ce ions over surprisingly large intervals of x and T. The low-temperature specific heat per Ce ion agrees quantitatively with that of an S=(1/2) Kondo impurity of ${T}_{K}$apeq23.3 K. These results strongly suggest that intersite correlations do not play the expected important role and that the high specific heat \ensuremath{\gamma} reported for ${\mathrm{CePb}}_{3}$ is mainly a manifestation of the single-ion Kondo resonance.

ELECTROKINETIC STUDIES OF MARINE OVA. VI. THE EFFECT OF SALTS ON THE ZETA POTENTIAL OF THE EGGS OF STRONGYLOCENTROTUS PULCHERRIMUS

1. The electrokinetic potentials of the unfertilized eggs of Strongylocentrotus pulcherrimus were measured in mixtures of various ratios of isotonic NaCl and CaCl2 and of NaCl and CeCl2.2. In the Na-Ca series, as the concentration of Ca-ions in the mixture was raised, the absolute magnitude of the negative potential of the eggs decreased. In the Na-Ce series, with the increase in concentration of Ce-ions, the sign of the zeta potential was reversed.3. At the isoelectric point, the eggs agglutinated.4. The course of the potential change can be attributed to the adsorption of the cations.5. The existence of a covering layer and its dissolution in the absence of Ca-ions such as were seen in Arbacia eggs have not been found in Strongylocentrotus eggs.