Terbium oxide

Lanthanum and samarium show virtually no NO dissociation activity even in the presence of Pt. These supports are not reducible and have no OSC property. The intrinsic NO dissociation activity of platinum is very weak, probably in reason of the low metal dispersion. The behavior of terbium oxide is more surprising. Although it is reducible in H2, it is unable to dissociate NO except in the presence of Pt. 

A stone quarry near the town of Ytterby in Sweden produces a large number of rare-earth elements. Carl Gustaf Mosander (1797-1858) discovered several rare-earths, including the rare-earth mineral gadolinite in this quarry in 1843. He was able to separate gadolinite into three separate, but closely related, rare-earth minerals that he named yttria (which was colorless), erbia (yellow color), and terbia (rose-colored). From these minerals, Mosander identified two new rare-earth elements, terbium and erbium. The terbia that was found was really a compound of terbium terbium oxide (Tb O )... 

The rates of internal conversion from the 5Z)3 to the 5D4 states were also measured. The backup oxide in this case was yttrium. This information was obtained by determining the rise time of the 5Z)4-state green fluorescence as a function of time, when the 5Z>3 state was excited. The rise time of the 5Z)4 state is, of course, the decay time of the 5Z>3 state. It was assumed that the decay of the 5Z)3 was predominantly due to an efficient internal conversion process to the 5D4. Measurements of the decay time of the 5Z)3 state directly were not possible, since the emission from this state is very weak if not, indeed, absent. The result of this study is shown in Fig. 23, where it can be seen that the internal-conversion time remains constant at about 17 fxsec up to a terbium oxide concentration of 1 mole per cent. At higher concentrations, the internal conversion time falls rapidly, until at 10 mole per cent terbium oxide the value is about 1.7 /xsec. This is down by a factor of 10 over samples containing 1 mole per cent or less of terbium oxide. 

Terbium oxide [12037-01-3J M 1471,1. Dissolved in acid, ppted as its oxalate and ignited at 650°. 

Careful analyses of the thermodynamic data of the praseodymium and terbium oxides led to the construction of their RCL-O2 phase diagrams (Hyde et al., 1966 Hyde and Eyring, 1965). The cerium oxides were studied by means of X-ray powder diffraction (Bevan, 1955) and the CeOx-02 phase diagram was constructed from equilibrium reaction studies at oxygen pressures down to 10-24 atm and temperatures up to 1200 °C (Bevan and Kordis, 1964 Ricken et al., 1984). It is worth to notice that the phase diagrams of Ce0x-02, PrCb-Cb, and Tb0x-02 systems... 

Several review articles and books on the lanthanide higher oxides, which include thermodynamic properties, have been published (Eyring, 1979 Haire and Eyring, 1994 Trovarelli, 2002 Adachi and Imanaka, 1998 Adachi et al., 2005). The systematic thermodynamic data of the cerium, praseodymium, and terbium oxides can be found in Bevan s and Eyring s papers (Hyde et al., 1966 Hyde and Eyring, 1965 Bevan and Kordis, 1964). 

Terbium oxide (Tb407, 99.99%) were obtained from Yue Long Chemical Plant (Shanghai, China), p-aminobenzoic acid (99.0%) were purchased from Beijing Chemical Company (Beijing, China). Isocyanatopropyltriethoxysilane (ICPTES) was obtained from Aldrich (USA). 

Cerium, praseodymium, and terbium oxides display homologous series of ordered phases of narrow composition range, disordered phases of wide composition range, and the phenomenon of chemical hysteresis among phases which are structurally related to the fluorite-type dioxides. Hence they must play an essential role in the satisfactory development of a comprehensive theory of the solid state. All the actinide elements form fluorite-related oxides, and the trend from ThOx to CmOx is toward behavior similar to that of the lanthanides already mentioned. The relationships among all these fluorite-related oxides must be recognized and clarified to provide the broad base on which a satisfactory theory can be built. 

Terbium occurs with other lanthanoids in minerals such as monazite, cerite, gadolinite, xenotime, and euxenite. In 2007, terbium oxide sold for about 850 per kilogram. 

EINECS 234-856-3 Terbium oxide Terbium oxide (Tb407) Tetraterbium heptaoxide. Atomergic Chemetals Cerac Rhdne-Poulenc. 

Yoshihara measured Tb in terbium oxide Tb O, and in terbium chloride solution by the sum peak pair method , and pointed out that the difference of the sum peak intensity ratio between two states could be enlarged by using comparison of a sum peak pair. This method has an advantage that the dependence of the sum peak pair ratio on the soun -detector distance is not as noticeable as that in the ordinary sum peak method. 

In general, the point defect in a crystal is a function of temperature, especially at higher temperature, but not sensitive to the environment oxygen pressure or temperature. However, the oxygen vacancy in cerium, praseodymium, and terbium oxides communicates with the environment oxygen. 

Disproportionation of the praseodymium and terbium oxides may also be induced by prolonged exposure to air, at room temperature [26,189]. As a result, Ln(OH)3 and Ln02 phases are formed. It would be therefore important to verify the likely occurrence of this phase segregation effect, because of its influence on the actual structural constitution and chemical behavior of the resulting material. Likewise, the formation of Ln(OH)3 (Ln Pr, Tb) may strongly favor the occurrence of dissolution/coprecipitation phenomena during the preparation of praseodymia (terbia) supported metal catalysts. These phenomena may induce nanostructural effects similar to those commented on above. 

Fig. 3-3 shows the phase diagrams for the cerium, praseodymium and terbium oxides. It reveals several phases in each of the systems with their compositions depending on temperature and oxygen partial pressure. The different phases have been named as i = MO1.714, C, = MOi.ysg, e = MOi.goo, 5 = MO1.8I8 and (3 = MO1.833. Electron diffraction patterns (see Fig. 3-21) revealed the unit cells of those phases and their relationship to the... 

A common feature of almost all of the known phases in the cerium, praseodymium and terbium oxide systems is the common a-axis which corresponds to the l/2 llV p vector (see Table 3-3). The odd members of the series, M 02n-2m) even exhibit a common c-axis which is a vector l/2[112]p. However the phase M62O112 has a different orientation for the a-axis of the supercell with respect to fluorite and modelling studies argue that these phase has divacancies like Pr70i2 [9]. The phase can be observed in thermoanalytical runs during oxidation of Pr70i2 but not in reduction on the higher temperature branch of the hysteresis loop. 

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