The hydration process of La2O3 studied by the electron spin resonance of Gd3+ and Mn2+ ions

Bacquet, G.; Bouysset, C.; Escribe, C.

doi:10.1016/0022-4596(76)90102-x

Cited by 8 publications

(2 citation statements)

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“…Comparing the weight increase in time interval 0−1 min with that in 1−2 min after exposure to water vapor, the latter case was larger than the former case, which suggests that there is an induction period, though very short, in the hydration of La 2 O 3 (A-type). Such an induction period has been observed in the hydration process for a single crystal of La 2 O 3 (A-type) . From the fact that for La 2 O 3 (A-type) and Nd 2 O 3 (A-type) as well as for La(OH) 3 and Nd(OH) 3 their crystal structures resemble each other, it can be reasonably presumed that the hydration process for La 2 O 3 (A-type) is similar to that for Nd 2 O 3 (A-type).…”

Section: Resultsmentioning

confidence: 62%

“…Since the surfaces of rare-earth oxides are heterogeneous, and hence the crystal planes cannot be specified, in addition to a similarity in the electronegativity for rare-earth elements, it is impractical to estimate the acidity (or basicity) on the basis of such models. For these reasons, we evaluated the basicity by using the Parks model that is relatively simple and capable of calculation of acidity (or basicity) on the basis of structural data.…”

Section: Resultsmentioning

confidence: 99%

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Hydration Process of Rare-Earth Sesquioxides Having Different Crystal Structures

et al. 2003

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The reactivity of rare-earth sesquioxides, mainly neodymium oxide, in water vapor and their hydration process have been investigated by measuring the adsorbed amounts, infrared spectra, and water contents. The adsorption of water vapor on neodymium oxides, A-type and C-type Nd2O3, led to the formation of a neodymium hydroxide, Nd(OH)3. The variation of adsorbed amounts (in weight) with exposure time to water vapor suggested that the hydration process is different depending upon the crystal structure of neodymium sesquioxides. Combining with the data of IR spectra and water contents, it has been revealed that the hydration of A-type Nd2O3 takes place in one step [into Nd(OH)3] after an induction period of about 30 min, while that of C-type Nd2O3 proceeds in two steps [into Nd(OH)3 via NdOOH]. The adsorption of water vapor on other rare-earth sesquioxides was also examined; the hydration process of A-type lanthanum oxide (La2O3) was similar to that of A-type Nd2O3, while those of C-type sesquioxides, Nd2O3, samarium oxide (Sm2O3), and yttrium oxide (Y2O3), were different from each other. The difference in the rates of hydration for these oxides can be correlated with a basic nature of oxide. Therefore, the rate of hydration is eventually governed by the ionic radius of rare-earth metal ion because the basicity of oxide depends on the ionic radius of metal ion. To make the Nd2O3 surface resistant to water, the surface modification or coating was also tried by adsorbing a metal-alkoxide vapor. As a result, it was revealed that the surface-coated neodymium oxide (i.e., titania-coated Nd2O3) has a water-resistant property.

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Section: Resultsmentioning

confidence: 62%

Section: Resultsmentioning

confidence: 99%