G. Cerrato et al., STRUCTURAL AND MORPHOLOGICAL MODIFICATIONS OF SINTERING MICROCRYSTALLINE TIO2 - AN XRD, HRTEM AND FTIR STUDY, Applied surface science, 70-1, 1993, pp. 200-205
Degussa P25 (mostly anatase) activated at T less-than-or-equal-to 873
K exhibits fairly regular Particles and mainly one family of strong co
ordinatively unsaturated Ti4+ sites, active towards CO at 77 K. After
firing at T greater-than-or-equal-to 1000 K, the phase becomes rutile,
the crystallites become larger, and their morphology becomes more irr
egular, while less and less uncoordinated Ti4+ sites are produced on a
ctivation, yielding CO bands absorbing at lower nu. The modifications
of crystal morphology and of surface activity towards CO are not due t
o the anatase-rutile phase transition, as a similar behaviour with fir
ing temperature is exhibited by pure rutile.