Praseodymium-oxygen system

Table 14.15 Intermediate phases formed by ordering of defects in the praseodymium-oxygen system...

Intermediate oxides of Cm that have stoichiometries between the sesquioxide and the dioxide have been reported (Noe and Fuger 1971, Stevenson and Peterson 1975). Oxides with O/M ratios of 1.50 to 1.65,1.714 (Cm.,Oi2), and 1.79 to 2.(K) are the structural groupings (bee, rhombohedral, and fee, respectively) which have been reported. The curium oxygen system bears some resemblance to both the plutonium and praseodymium oxygen systems but additional work is needed on it. 

Figure 3-3. Phase diagrams for the cerixun, praseodymium and terbium oxygen system (see [11]).

In order to prepare an oxide in this wide composition range, one must equilibrate the oxide at temperatures and oxygen pressures higher than those listed in table 3 for the intermediate compounds. Figure 6 epitomizes the intricacies of the praseodymium oxide system with more or less vertical or slanted single-phase regions, horizontal two-phase regions that show hysteresis. The nearly vertical lines mark the ordered... 

Phase Transformations in the Praseodymium Oxide-Oxygen System High Temperature X-Ray Diffraction Studies, D.A. Burnham and L. Eyring, J. Phys. Chem., 72,4415 1424... 

On the Phase Interval PrOi.50 to PrOui in the Praseodymium Oxide-Oxygen Systems, R. Turcotte, J. Warmkessel, R.J.D. Tilley and L. Eyring, J. Solid State Chem., 3,265-272 (1971). 

Burnham DA, E5rring L. Phase transformations in the praseodymium oxide-oxygen system high-temperature x-ray diffraction studies. J. Phys. Chem. 1968 72 4415-4424. DOI 10.1021/jl00859a010. 

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... 

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... 

Attempts have been made to force praseodymium, which follows cerium in the lanthanide series, into an intermediate valent state. Since all intermetallic systems have a Pr ion with a valence close to three, pressure was applied to some of these systems, but all efforts have failed. Enhanced hybridization, however, was found in insulating Pr systems containing oxygen. Within the RBa2Cu307 a series, which usually exhibit high-temperature superconductivity, the suppression of superconductivity in PrBa2Cu07... 

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