Particle Size Control of YAG-Based Phosphors via Urea-Based Liquid-Phase Method and Manufacturing Method Thereof

Manufacturing YAG:Ce Phosphors for White LEDs with Controlled Particle Size Using Urea-Based Liquid-Phase Reaction

This technology is a liquid-phase synthesis method for GaN-based blue-excited YAG:Ce yellow phosphors. It involves mixing yttrium, aluminum, and cerium nitrates with an aqueous urea solution to obtain a precursor at 400°C, followed by calcination at 1100–1600°C. Particle size is controlled from the nanometer to micrometer scale through calcination temperature, time, and a reflux process.

Conventional YAG:Ce phosphors were produced via high-temperature solid-state reactions exceeding 1600°C, leading to high energy consumption and the formation of intermediate phases like YAM and YAP due to poor mixing and low reactivity. Particle sizes were widely distributed between 1–10μm, and it was previously believed that liquid-phase methods could not control particle size.

This technology uses urea-based liquid-phase mixing to ensure uniform distribution of Ce3+ activators within the YAG matrix, yielding pure phosphors with a narrow particle size distribution at lower temperatures than solid-state methods. By selecting secondary heat treatment conditions, uniform powders ranging from 50nm to 2μm can be produced reproducibly. Applicable to white LED and display backlight phosphor production, it allows for direct adjustment of particle size to fit specific package structures.

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Key Features:

• Preparing an aqueous solution of starting materials Y(NO3)3, Al(NO3)3, and Ce(NO3)3 by uniformly mixing them with an aqueous urea solution
• Performing a primary heat treatment on the mixed solution in an electric furnace at 400°C for 30 minutes to obtain a precursor
• Heating the precursor at a rate of 10°C/min and performing a secondary heat treatment for 1 hour at a selected temperature of 1100°C, 1200°C, 1400°C, or 1600°C
• Obtaining uniform YAG:Ce phosphor powder with a particle size of 50nm to 2μm and increasing the particle size through a reflux process

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This invention was developed with support from the Ministry of Education, Science and Technology/Ministry of Knowledge Economy for the development of YAG:Ce inorganic phosphors for LEDs.

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