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Diekemper, Dominik; Schnick, Wolfgang; Schwarzer, Stefan (2019): Microwave Synthesis of a Prominent LED Phosphor for School Students: Chemistry's Contribution to Sustainable Lighting. In: Journal of Chemical Education, Vol. 96, No. 12: pp. 3018-3024
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Abstract

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.