Production of Phosphor (YAG : Tb) particles by Supercritical Water Crystallization Method

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The objective of this research was to develop a repid and continuous production process for phosphor (YAG : Tb) fine particles by supercritical water crystallization method. The relationship between properties (crystal sturacture, particle size and particle size distribution) of particles produced and reaction conditions (reaction temperature, pressure, reaction time, composition of solution and alkali mole ration of solution) was investigated experimentally. Al (NO_3) _3, Y (NO_3) _3 and TbCl_3 mixed aqueous solution was used as the starting materials. Potassium aqueous solution was used to vary the alkali mole retio of solution. Experiments were performed with a newly-deveolped flow type apparatus. From these results, the alkali mole ratio was important factor for production of single phase YAG particles. Reaction temperature and pressure affected crystalline size and lattice constant of particles. High temperature and low pressure leaded to produce particles with high crystallinity. Emission properties of particles produced was studied by comparison with particles produced by a conventional solid state reaction method. Properties of particles produced by the method in this work were comparable with the conventional method. Continuous (1.5g/h) and rapid (<1 sec.) production of phosphor (YAG : Tb) fine particles was found to be practical with the supercritical water crystallization method.