(Georgia Institute of Technology, 1999-03-22)
Jiang, Yongdong; Zhang, Fuli; Summers, Christopher J.; Wang, Z. L. (Zhong Lin)
A blue emission powder phosphor Sr₂CeO₄ for field emission displays was prepared using a chemical coprecipitation technique, which is most suitable for large-scale production. The powders were fired at different temperatures to optimize the properties. Firing the powder at 1200 °C for 2 h gave the highest luminescence efficiency of 5.4 lm/W at 4 kV and 29.0 lm/W at 10 kV. The emission peak of this phosphor is at ~ 470 nm and Commission International de l'Eclairage coordinates are x = 0.19, y = 0.26.
(Georgia Institute of Technology, 1998-10)
Jiang, Yongdong; Wang, Z. L. (Zhong Lin); Zhang, Fuli; Paris, Henry G.; Summers, Christopher J.
A forced hydrolysis technique is used for preparing Y₂O₃: Eu³⁺ powders at low processing temperatures. The technique uses yttrium oxide, europium oxide, nitric acid and urea, and has the potential for large-scale production for industrial applications. Several experimental conditions have been examined to optimize the luminescence efficiency. The best result was found to be at 2 mol% Eu doping and a 2 hour firing of 1400°C. Micro-structural information provided by x-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been applied to interpret the observed luminescent properties
(Georgia Institute of Technology, 1997-06-23)
Wang, Z. L. (Zhong Lin); Yin, Jinsong; Jiang, Yongdong; Zhang, Jiming
Using the white line intensities, electron energy-loss spectroscopy in a transmission electron microscope has been employed to characterize the valence conversion and oxygen vacancies in La₁₋ₓCaₓMnO₃₋[subscript y]. For a nominal doping composition x = 0.33, the ratio of Mn³⁺ to Mn⁴ ⁺ is determined to be more than 0.25 but less than 0.5, and the content of oxygen vacancy y is no more than 0.065 (equivalent to 2.2 at. % of the oxygen content). At y[subscript max] = 0.065, 60% of the residual charge introduced by Ca doping is balanced by the conversion of Mn³⁺ to Mn⁴ ⁺and 40% by oxygen vacancy.