On phosphor degradation mechanism: thermal treatment effects

Enhanced Optical Performance of BaMgAl10O17:Eu2+ Phosphor by a Novel Method of Carbon Coating

“…It possesses high quantum efficiency (around 80%), good chromaticity, and strong absorption in the vacuum ultraviolet excitation band, making it widely used in three-band fluorescence lamps, plasma display panels (PDPs), and white light-emitting diode (LED). [1][2][3][4] However, the oxidation resistance of BAM is rather poor. The BAM phosphor will undergo a decrease of luminescence intensity during post-treatment processes, for example, irradiation by ultraviolet photons, ion sputtering, and baking process in air during PDP manufacture.…”

“…[4][5][6][7] So far, many researchers have tried to enhance the oxidation resistance at high temperature of BAM phosphor, and many methods, such as coating, co-doping, compositional variation, and annealing in a non-oxidizing atmosphere, have been proposed. 5,[8][9][10][11][12][13][14] Among these methods, covering the phosphor particle surface with a coating is an effectively applied technique to enhance the chemical stability of BAM phosphor.…”

“…5,[8][9][10][11][12][13][14] Among these methods, covering the phosphor particle surface with a coating is an effectively applied technique to enhance the chemical stability of BAM phosphor. Up to now, several inorganic materials have been reported as the coating materials such as SiO 2 , MgO, Al 2 O 3 , AlPO 4 , and LaPO 4 and so forth. [14][15][16][17] It is well known that Eu 2+ is easily oxidized to Eu 3+ , and all the materials mentioned above are oxides.…”

On the kinetics of thermal oxidation of the thermographic phosphor BaMgAL 10 O 17 :Eu

“…(dashed-blue) presents a significant mass gain at the beginning of the curve, which might be related to adsorption of oxygen on vacancies at the surface of the phosphor [9]. Later, the mass reduces due to water evaporation and does not present any further changes above 250 °C.…”

“…However, the manufacture of these devices usually involves heat treatment in air at a relatively high temperature (about 600 °C), and the photoluminescence of the phosphor is then decreased due to thermal degradation that results in oxidation of the dopant ion from Eu 2+ to Eu 3+ and a substantial reduction in blue emission. This thermal degradation has been a common subject of study in recent years with the objective of understanding the mechanisms by which the phosphor degrades and thereby being able to fabricate a more resistant phosphor that remains efficient even after the necessary heat treatment [4][5][6][7][8][9][10]. The literature in the field, however, suggests that understanding remains incomplete and some of the mechanisms suggested are contradictory.…”