TY - JOUR
T1 - In situ phase transition study of nano- and coarse-grained TiO2 under high pressure/temperature conditions
AU - Wang, Yuejian
AU - Zhao, Yusheng
AU - Zhang, Jianzhong
AU - Xu, Hongwu
AU - Wang, Liping
AU - Luo, Sheng Nian
AU - Daemen, Luke L.
PY - 2008/3/26
Y1 - 2008/3/26
N2 - A comparative phase transition study of nanocrystalline and micro-TiO 2 has been conducted under high pressure-temperature (P-T) conditions using energy-dispersive synchrotron x-ray diffraction (XRD). Our study reveals that on compression at room temperature, the micro-tetragonal anatase-type TiO2 started to transform to the orthorhombic columbite-type TiO 2 near 1.6 GPa. In contrast, we did not observe this phase transition in nano-anatase at pressures of up to 8.5 GPa. At 8.5 GPa, by applying moderate heat, both samples were transformed completely to columbite-type TiO 2 almost simultaneously, indicating that heat treatment could significantly expedite this phase transition. These columbite-type TiO 2 phases were quenchable because after cooling them to room temperature and decompressing them to 2.0 GPa, the XRD patterns displayed no changes in comparison with those collected at 8.6 GPa and 1270 K. At 2 GPa, we heated the specimens again, and the rutile-type TiO2 started to emerge around 970 K. This phase was also quenchable after cooling and releasing pressure to ambient conditions. The grain size effects on the phase transition were discussed based on the kinetics mechanism. This study should be of considerable interest to the fields of materials science and condensed matter.
AB - A comparative phase transition study of nanocrystalline and micro-TiO 2 has been conducted under high pressure-temperature (P-T) conditions using energy-dispersive synchrotron x-ray diffraction (XRD). Our study reveals that on compression at room temperature, the micro-tetragonal anatase-type TiO2 started to transform to the orthorhombic columbite-type TiO 2 near 1.6 GPa. In contrast, we did not observe this phase transition in nano-anatase at pressures of up to 8.5 GPa. At 8.5 GPa, by applying moderate heat, both samples were transformed completely to columbite-type TiO 2 almost simultaneously, indicating that heat treatment could significantly expedite this phase transition. These columbite-type TiO 2 phases were quenchable because after cooling them to room temperature and decompressing them to 2.0 GPa, the XRD patterns displayed no changes in comparison with those collected at 8.6 GPa and 1270 K. At 2 GPa, we heated the specimens again, and the rutile-type TiO2 started to emerge around 970 K. This phase was also quenchable after cooling and releasing pressure to ambient conditions. The grain size effects on the phase transition were discussed based on the kinetics mechanism. This study should be of considerable interest to the fields of materials science and condensed matter.
UR - http://www.scopus.com/inward/record.url?scp=40549103795&partnerID=8YFLogxK
U2 - 10.1088/0953-8984/20/12/125224
DO - 10.1088/0953-8984/20/12/125224
M3 - Article
AN - SCOPUS:40549103795
SN - 0953-8984
VL - 20
JO - Journal of Physics Condensed Matter
JF - Journal of Physics Condensed Matter
IS - 12
M1 - 125224
ER -