The Structure And Optical Characteristic Of Sm-doped And Gd-doped Nano-TiO₂ Powders

Pure TiO₂, Sm-doped and Gd-doped nano-TiO₂ powders are prepared by sol-gel process. The samples are annealed at 400℃, 600℃and 800℃. The absorbency characteristic and XRD were mersure. The phase structure, the sample's size and crystal cell volume are analysed. We get the optical band gap by extrapolation according to absorption curve.The analyse shows that Sm-doping and Gd-doping improve the phase-changing temperature of the samples. Sm-doping doesn't make TiO₂ produce new phase while Gd-doped TiO₂ appeares Gd₂Ti₂O₇. Doping reduces the size of the nano-TiO₂ obviously. The sample's size will diminish with the doping percent's rising and grow with the annealing temperature's increasing. Doping makes the sample occur lattice distortion. The Sm-doped sample's a increases and c minishes with the doping percent's rising while a minishes and c increases with the annealing temperature's increasing, but the crystal cell volume doesn't present monotone and expresses a distortion of each direction. To the Gd-doped sample, the value of a and c becomes small gradually when the annealing temperature rises. The value of a becomes big and c minishes when the doping percent increases to 1% from 0.5%, but a minishes and c rises when the doping percent reaches 3%, the value of a and c becomes small when the doping percent increases to 5% from 3%. Sm-doping decreases the nano-TiO₂'absorption a little while Gd-doping makes the nano-TiO₂'absorption rises obviously. But the doping percent has little effect on the nano-TiO₂'absorption. The absorption will decrease when the annealling temperature rises. Sm-doping and Gd-doping make the nano-TiO₂'optical band gap largen a little. The optical band gap becomes narrower with the annealing temperatue rises. When the doping percent is more than 1%, the sample's optical band gap becomes narrower with the doping percent's decreasing but to the Gd-doped samples, the truth is just contrary when the doping percent is less than 1%.