Thermal rare earth aluminates

We previously proposed an interpretation of thermal stabilization of supported catalysts by rare-earth elements [10, 11, 18] by means of interfacial structural coherence between alumina and rare-earth aluminates. This model, developped for lanthanum and neodymium, can be easily extended to cerium since LaAlOs, NdAlOs and CeAlOs are iso-structural mixed oxides with identical lattice parameters (a = 7.6 A). 

In contrast to orthorhombic aluminates, RAIO3 compounds with rhombohe-dral structures display no anomalies both in the low- and high-temperature expansion (Figure 50). For rhombohedral perovskites, the thermal expansion in the fl-direction is smaller compared with the c-direction (0.75% and 1% at 1200 K, respectively). The Pa and pc values are practically identical for all rhombohedral rare earth aluminates (Figure 50B and D). The analysis of some representatives of Ri xR x AIO3 solid solutions shows that the character of their thermal expansion is... 

From Table 29 and Figure 52A, it is evident that the linear thermal expansion coefficients for orthorhombic rare earth aluminates in the temperature range of 300-1200 K lie within the limits a = (8.9-11.3) x 10 = (3.8-7.S) x 10 ... 

On the other hand, Kato et al. (1988) studied the addition of different rare-earth oxides to V-AI2O3 in a 5/95 ratio. They found that in those systems where (1-aluminates were detected after firing at 1473 K the surface area was always higher than in those cases where only (X-AIO3 was detected. They concluded that the common feature of thermally resistant supports is that they have a layered aluminate structure which retards support sintering. 

Liu RH, Zhuang WD, Huang XW, Hu YS, He HQ (2009) Thermal degradation pioptaties of barium magnesium aluminate blue phosphor. J Chin Rare Earths Soe 27 178... 

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