Microwave Synthesis of a Prominent LED Phosphor for School Students: Chemistry’s Contribution to Sustainable Lighting
Summary
Scarcer raw materials and climate change are scientific facts that make it necessary to enhance energy efficiency and to recycle raw material. Fundamental researchers at universities as well as in industry agree that light-emitting diodes (LEDs) are the most efficient and sustainable light sources of the future. Chemistry plays a significant role in the development of white, energy-efficient LEDs; however, students and society do not seem aware of this role. This paper presents a school-student-friendly synthesis of cerium-doped yttrium aluminum garnet (YAG:Ce) in a laboratory microwave oven. YAG:Ce is the most widely applied luminescent material (“phosphor”) used in white LEDs. The initial blue light of a gallium nitride-based primary LED is partly down-converted by the YAG:Ce phosphor on top of the LED chip, resulting in yellow-green emission. Additive color mixing (blue + yellow-green) results in cold-white light generation. This experiment aims to demonstrate chemistry’s contribution to sustainable development in a comprehensible way. On the basis of such phosphor-converted LEDs, the interdependence of and cooperation between different scientific disciplines are outlined. The critical question of the related raw materials, in this case especially rare earth elements (REEs), their lifetime, and their possible recycling, represents another important issue for sustainable development and systems thinking and is shown in this example from everyday life.
Full citation: Diekemper, D., Schnick, W., & Schwarzer, S. (2019). Microwave Synthesis of a Prominent LED Phosphor for School Students: Chemistry’s Contribution to Sustainable Lighting. Journal of Chemical Education, 96(12), 3018–3024. https://doi.org/10.1021/acs.jchemed.9b00464
Full citation: Diekemper, D., Schnick, W., & Schwarzer, S. (2019). Microwave Synthesis of a Prominent LED Phosphor for School Students: Chemistry’s Contribution to Sustainable Lighting. Journal of Chemical Education, 96(12), 3018–3024. https://doi.org/10.1021/acs.jchemed.9b00464
Safety Precautions, Hazards, and Risk Assessment
Safety goggles should be worn all the time during the experimental procedure. UV light excitation is harmful to the retina, so anti-UV coated goggles should be worn for safety reasons.
Wear protective gloves while handling REE-nitrates.
Because of the development of large amounts of gases such as N2, CO2, and H2O, the laboratory microwave oven must be placed in a fume cupboard during synthesis, even though the gases are exhausted separately. It is advisible to control the microwave by a main switch in order to enable an emergency shutdown. The microwave oven used for this experiment cannot be used for further food preparation.
High-temperature protective gloves and crucible tongs should be used due to the high temperature of the porcelain crucible.
Leftover product remaining in the crucible is dissolved in water and should be transferred into a container designated for metal salts.
Wear protective gloves while handling REE-nitrates.
Because of the development of large amounts of gases such as N2, CO2, and H2O, the laboratory microwave oven must be placed in a fume cupboard during synthesis, even though the gases are exhausted separately. It is advisible to control the microwave by a main switch in order to enable an emergency shutdown. The microwave oven used for this experiment cannot be used for further food preparation.
High-temperature protective gloves and crucible tongs should be used due to the high temperature of the porcelain crucible.
Leftover product remaining in the crucible is dissolved in water and should be transferred into a container designated for metal salts.
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