Date of Award
Master of Science (MS)
Department of Chemistry
Eirin C. Sullivan
Typical lighting systems such as incandescent and fluorescent bulbs are common in homes but are rather inefficient compared to the newer light emitting diodes (LEDs). LED-based lamps can be constructed to generate white light by combining a red, green, and blue LED, or by using an LED light source (typically with a low wavelength) with a complimentary phosphor coating to produce white light. The latter, known as phosphor-conversion (PC) LEDs, is the primary focus of this research, looking specifically at rare earth-free options for these phosphor coatings.
Anti-perovskites are a potential lattice type for this type of conversion, in particular the A3MO4F (A= Sr, Ba, Ca; M= Al, Ga) tetragonal structure. Photoluminescence has been observed in the Sr3AlO4F system upon doping with various lanthanides, but rare earth metals are expensive, scarce due to increased use in new technologies, and their mining process introduces toxins into the environment. Focusing on doping without rare earth metals will prove beneficial as people are becoming more conscientious of their carbon footprint and new dopants will lower the cost for the consumer.
Isovalent and aliovalent doping on the Sr3AlO4F lattice has been demonstrated on the A site (Sr), and this proven technique has introduced many rare earth trivalent cation ions as successful dopants. Doping on the M site (Al) is less studied but various non-rare earth (RE) cations such as Ga3+, Si4+, and In3+ have been incorporated on this site, making this site the primary focus of this thesis. The specific cations investigated are P5+, Y3+, and Hf4+ to expand the range of isovalent dopants and determine if aliovalent doping can be achieved on this site. High temperature synthesis was used to synthesize the novel products Sr2.5-xBa0.5Al1-xPxO4F, Sr3-xAl1-xYxO4F, andSr_(2.5-x/2) Ba_0.5 Al_(1-x) Hf_x O_4 F. The structures of these oxyfluorides were analyzed via powder X-ray diffraction (PXRD) and neutron powder diffraction (NPD), and their photoluminescent properties were analyzed through spectrofluorimetry before and after being treated under reducing conditions.
Keil, Sean Thomas, "Solid State Synthesis and Characterization of the Rare Earth-Free Anti-perovskites Sr2.5-Xba0.5 Al1-Xp Xo4 F ( 0 ≤ X ≤ 0.15 ), Sr3al1-Xy Xo 4 F ( 0 ≤ X ≤ 1 ), and Sr2.5-x/2ba0.5 Al1-Xhfxo4 F ( 0 ≤ X ≤ 0.1 ) as Potential Phosphor Materials" (2016). Theses and Dissertations. 510.