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Sintering and crystallization of low-density polyethylene glycol (PEG) and  lanthanum, La(III)-doped Al2O3 aerogels prepared from aluminum isopropoxide  were investigated. The sintering behavior of non-doped and doped aerogels was  examined by following the change of specific surface area with isothermal  heat-treatment. The specific surface area and crystalline phases of non-doped  and PEG+La(III)-doped aerogels were determined, and the effects of dopants on  the sintering and crystallization of Al2O3 aerogels are discussed. Isothermal  sintering experiments showed that the sintering mechanism of non-doped and  PEG+La(III)-doped Al2O3 aerogels is surface diffusion. The specific surface  areas of alumina samples decrease rapidly during the initial period of  sintering, and more slowly with prolonged sintering time. The change of the  porous structure is correlated with the phase transformation of γ-Al2O3  during calcinations of Al2O3 aerogels. The surface area of non-doped Al2O3  aerogels came to about 20 m2g-1 with heat-treatment at 1100°C because of  crystallization of α-Al2O3 after densification. In the case of heattreatment  at 1200°C, the largest surface area was observed for PEG+La(III) doped Al2O3  aerogels and the XRD pattern showed only low ordered θ-Al2O3. These indicate  that the addition of PEG+La(III) to boehmite sol prevents Al2O3 aerogels from  sintering and crystallizing to the α-Al2O3 phase. Even after 20 h at 1000°C,  PEG+La (III)-doped alumina samples maintain a rather good specific surface  area (108 m2 g-1) in comparison to the non-doped, containing mainly θ-Al2O3  and minor amounts of δ-Al2O3. Aluminum-oxides with these structural and  textural properties are widely used as a coatings and catalyst supports in  the field of various catalysis

Kinetic of sintering of polyethilene glycol and lanthanum dopped aluminum oxide obtained by the sol-gel method