高温氧气热处理对TiO_2晶体结构和铁磁性的影响

金红石TiO_2晶体先在真空中进行退火处理,随后在1173 K的氧气中进行不同时间(2 h、5 h、8 h)的热处理.理论上,通过Doppler程序计算了晶体中存在单空位、双空位和间隙O原子时的正电子湮没寿命.实验上,利用正电子湮没寿命谱仪、符合多普勒能谱仪和超导量子干涉仪分别表征了氧气退火后晶体内部的缺陷结构和常温铁磁性.分析结果得出:真空退火晶体的常温铁磁性主要与O空位的存在相关联;而经过氧气退火后,虽然极大地减少了氧空位,但晶体中却产生了大量的Ti双空位,这使得晶体的常温铁磁性有所增加.

Influence of crystal structure and ferromagnetism of TiO2 annealed on high temperature oxygen

Rutile TiO2 crystals firstly are annealed on vacuum. Then they are treated by oxygen about 1173 K at different times (2 h, 5 h, 8 h). Theoretically, we calculate positron annihilation lifetime of crystals including single crystal vacancy, double vacancy or interstitial O atom by Doppler program. Experimentally, we measure defect structures and room temperature ferromagnetism of crystals, annealed on high temperature oxygen, by positron annihilation lifetime apparatus, coincident Doppler broadening apparatus and superconducting quantum interference device. The result is that room temperature ferromagnetism of crystals annealed on vacuum is mainly associated mainly with O vacancies. TiO2 crystals, annealed by high temperature oxygen, have little O vacancies. But crystals generate lots of Ti divacancies, which make the room temperature ferromagnetism of crystals increase obviously.