锐钛矿金红石的高温原位X射线衍射研究

In situ high temperature X-ray diffraction study of anatase and rutile

对TiO2粉末进行了空气和真空条件下从室温到1200℃的加热原位X射线衍射实验,得到了空气和真空条件下微米级锐钛矿颗粒转变为金红石的起始温度分别为850℃和855℃;分别修正了空气条件下锐钛矿在(27—850℃)范围和金红石在(900—1200℃)范围内的晶胞参数和真空条件下锐钛矿在(27—850℃)范围和金红石在(950—1200℃)范围的晶胞参数,从而得到了晶胞参数随温度变化的关系,得到了锐钛矿和金红石在空气中和真空中的热膨胀系数,并总结了热膨胀系数随温度变化的规律.室温下锐钛矿在空气条件下的热膨胀系数为αa=4.55063×10-6/℃,αc=7.7543×10-6/℃,β=16.85836×10-6/℃;真空下为αa=4.69429×10-6/℃,αc=9.02850×10-6/℃,β=18.69688×10-6/℃.室温下,金红石在空气条件下的热膨胀系数为αa=6.81243×10-6/℃,αc=8.71644×10-6/℃,β=22.22178×10-6/℃;真空条件下为αa=6.05834×10-6/℃,αc=8.39280×106/℃,β=20.52362×10-6/℃.

In situ X-ray diffraction patterns of the powder titania polymorphs are recorded in a temperature range from room temperature （RT） to 1200℃ in static air and vacuum. The results show that the temperature converting anatase into rutile is at 850℃ in static air and at 855 C in vacuum. Lattice parameters for anatase （RT-850 C） and rutile （RT, 900–1200℃） in static air and those for anatase （27–850℃） and rutile （950–1200℃） in vacuum are refined. The variations of lattice parameters of anatase and rutile with temperature （℃） are therefore well described. Linear （α） and volume （β ） thermal expansion coefficients of anatase （RT-850℃） and rutile （RT, 900–1200℃） are calculated. The change laws of α and β with temperature for anatase and rutile in static air and vacuum are summarized. At RT, the thermal expansion coefficients for anatase are α a = 4.55063 × 10-6 /℃, α c = 7.7543 × 10-6 /℃, and β = 16.85836 × 10-6 /℃ in static air and α a = 4.69429 × 10-6 /℃, α c = 9.02850 × 10-6 /℃, and β = 18.69688 × 10-6 /℃ in vacuum while those for rutile are α a = 6.81243 × 10-6 /℃, α c = 8.71644 × 10-6 /℃, and β = 22.22178 × 10-6 /℃ in static air and α a = 6.05834 × 10-6 /℃, α c = 8.39280 × 10-6 /℃, and β = 20.52362 × 10-6 /℃ in vacuum, respectively.