Dopant content

The dependence of the X-ray-excited emission intensities on the amount of doped Eu are shown in Fig. 21.24. The intensity of the phosphors increases with the dopant content up to a maximum (x=0.0S) and then it decreases. 

FIGURE 1.7 Resistivity plots for ScSZ as a function of the dopant content both before and after annealing at 850 and 1000°C [31]. 

Fig. 4 Selective reflection wavelength (optical pitch) as a function of temperature for three samples host material showing SmC and SmCA without dopant, with 1% and 3% dopant The chemical structures of the rod-shaped host and the bent-shaped dopant molecules are also shown. As shown in inset, inverse pitch increases almost linearly with dopant content [4]...

Fig. 6 Reciprocal optical pitch as a function of dopant content. Host material is a cholesterol derivative used in the enhanced chirality in N with bent-core molecules [5]...

Fig. 18. Dopant content x dependence of thermal expansion coefficient of La xSrxMn03 at 800 and 960 °C. From ref. [76],...

The exact dopant contents may change, depending on the fabrication process and cell configuration. Generally, cathodes with x = 0.16 are used and the porosity ranges from 30 to 40%. 

Figure 10 Influence of TMB flow on dopant content of TEOS-BPSG films.7...

Figures 6.37 and 6.38 show the variation of electrical properties as a function of the dopant content of ZnO films. Figure 6.37 shows the case of AP-CVD ZnO F with fluorine as dopant (here, the fluorine atomic fraction is considered as dopant content). Figure 6.38 shows the case of LP-CVD ZnO B with boron as dopant (here, the B2H6/DEZ ratio is considered as dopant content). The electrical properties taken into consideration are the conductivity a, the resistivity p, the mobility //, and the free carrier density N.

The other application of the LP measurements is to evaluate strains in the heteroepitaxial layers and/or native defect and dopant content. The latter application has not been explored for nitrides yet. 

Figure 7 shows the solutions obtained by the more accurate Eq. (39) for both concentrations and conductivities. As soon as the dopant content becomes appreciable, it correspondingly increases the concentration of the oppositely charged defect which depresses the active counter-defect via mass action. In AgCl the mobility of the silver interstitials exceeds that of the vacancies leading to a minimum in the overall ion conductivity approximately at KpUj /uv as can be readily... 

It is known that as the dopant content increases, the conductivity rises, but reaches a maximum followed by a steep decrease. The exact dopant concentration for maximum conductivity depends to some extent upon the dopant type, but is generally around 10 - 15% mol for trivalent dopants. 

Oxygen migration in doped cerias has been recently studied with molecular dynamics methods by Inaba et al and Hayashi et These authors examined the systems (Ce02)i (A 203) /2 (where M = Y Gd La) with dopant contents in the range 0 — 15% mol. The diffusion coefficient of oxygen at 1273 K was evaluated from the simulations at different compositions with a maximum at around 10% mol of dopant. 

In contrast, significant increases in the specific activity of Rh in the CO/H2 and CO2/H2 reactions were observed when the metal was dispersed on W -doped Ti02 carriers [106-108]. The kinetic results are summarized in Figure 8(a), which shows the ratio of the turnover frequency (TOF) of the doped catalysts over that of the undoped catalysts as a function of dopant content in the Ti02 carrier. Doped catalysts were found to be up to 20 times more active in CO2 methanation. The... 

The apparent activation energy of both reactions was found to decrease when they were carried out over the doped Rh catalysts. The decrease was found to be about 20 kJ moP for the CO/H2 reaction and 25-30 kJ moP for the CO2/H2 reaction, almost independent of the dopant content in the Ti02 support. Doped Rh catalysts also exhibited superior stability with time on stream in both reactions. While the activity of the undoped Rh catalyst declined by about 30-50% in the first 3 h on stream, the activity of the doped catalysts remained practically constant even after 4—5h on stream. This implies that carbon deposition is retarted on doped catalysts, a phenomenon also investigated by temperature programmed surface reaction techniques [107]. 

Figure 9 Effect of gas-phase composition on the activity enhancement ratio (TOF)d/ (TOF)und in the CO/O2 reaction over Rh catalysts as a function of dopant content. (From Ref. 107.)...

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