LiAlO2 single crvstals doped with Ti at concentration 0.2at.% are grown by the Czochralskl technique with dimensions φ42×55mm. Ti ions in the crystal are quadrivalence proven by comparing the absorption and fluo...LiAlO2 single crvstals doped with Ti at concentration 0.2at.% are grown by the Czochralskl technique with dimensions φ42×55mm. Ti ions in the crystal are quadrivalence proven by comparing the absorption and fluorescence spectra of pure LiAlO2 and Ti： LiAlO2. After air and Li-rich atmosphere annealing, the absorption peaks in the range of 600-800nm disappear. We conclude that 682 and 756nm absorption peaks are attributed to the VLi and Vo absorptions, respectively： The peaks at 716nm and 798nm may stem from the VLi^＋ and absorptions. The colour-centre model can be applied to explain the experimental phenomena. Ti^4＋-doping produces more lithium vacancies in the LiAlO2 crystal. The intensities of [LiO4] and the associated bonds remain unchanged, which improves the anti-hydrolyzation and thermal stability of LiAlO2 crystals.展开更多
The electrostaticfieldin 500 kVpotentialtransformers has been simulated withthree dimensional(3 D) models.The main purpose ofcalculatingthe electrostaticfieldistoinvestigatethe effectofelectrostatic shieldingin tr...The electrostaticfieldin 500 kVpotentialtransformers has been simulated withthree dimensional(3 D) models.The main purpose ofcalculatingthe electrostaticfieldistoinvestigatethe effectofelectrostatic shieldingin transformers andto seeifthe shielding can be removed.The conclusions arethatthe shielding onthe middle ofthe windingis not clearly profitable to the maximum electrostaticfield strength and can be removed.To calculate the field a 3 Dfinite elementsoftware has been developed which is based on a powerfultetrahedral mesh generator. Meanwhile ,axisymmetric models are also employed to simulate the effectofthe shielding.展开更多
文摘LiAlO2 single crvstals doped with Ti at concentration 0.2at.% are grown by the Czochralskl technique with dimensions φ42×55mm. Ti ions in the crystal are quadrivalence proven by comparing the absorption and fluorescence spectra of pure LiAlO2 and Ti： LiAlO2. After air and Li-rich atmosphere annealing, the absorption peaks in the range of 600-800nm disappear. We conclude that 682 and 756nm absorption peaks are attributed to the VLi and Vo absorptions, respectively： The peaks at 716nm and 798nm may stem from the VLi^＋ and absorptions. The colour-centre model can be applied to explain the experimental phenomena. Ti^4＋-doping produces more lithium vacancies in the LiAlO2 crystal. The intensities of [LiO4] and the associated bonds remain unchanged, which improves the anti-hydrolyzation and thermal stability of LiAlO2 crystals.
文摘The electrostaticfieldin 500 kVpotentialtransformers has been simulated withthree dimensional(3 D) models.The main purpose ofcalculatingthe electrostaticfieldistoinvestigatethe effectofelectrostatic shieldingin transformers andto seeifthe shielding can be removed.The conclusions arethatthe shielding onthe middle ofthe windingis not clearly profitable to the maximum electrostaticfield strength and can be removed.To calculate the field a 3 Dfinite elementsoftware has been developed which is based on a powerfultetrahedral mesh generator. Meanwhile ,axisymmetric models are also employed to simulate the effectofthe shielding.
