Thesis completed in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Ceramic Engineering at the Inamori School of Engineering, New York State College of Ceramics at Alfred University
The aim of this work is to fabricate a p-type CuAlO2 conducting oxide via electrospinning process and to develop a new photoluminescence (PL) functionality by introducing trivalent dopants. The proposed trivalent doping method is also inspired by the poor enhancement in electrical properties observed with divalent ion doping, as well as the results of simulations that predict a possible enhancement in electrical properties through substitutional trivalent doping.
This work starts with preparing solution-based precursors, followed by electrohydrodynamic processing and post-calcination. Two regimes exist in electrohydrodynamic processing: electrospraying and electrospinning, with the transition between the two dictated by polymer concentration in the starting solution, with higher polymer contents corresponding to the electrospinning regime. The effects of deposition and heat-treatment conditions on the microstructural evolution and phase transformation were investigated. Meanwhile, a mathematical model based on Newton's second law was constructed to model and simulate jet behavior during electrospinning. The simulation results indicate that a stabilized jet can only travel for a relatively short distance before whipping occurs, with this distance dependent on solutions viscosity. The volume charge density of the jet follows a log-linear relationship with terminal fiber diameter, which demonstrates that an equilibrium between surface tension and electrostatic force is established during the electrospinning process.
The photoluminsecence properties introduced by lanthanide ion doping and the effects of trivalent dopants on the electrical properties are investigated. An optical-oriented probing method is proposed to examine the effects of trivalent substitutions on Cu-O hybridizations. The CuAlO2 in the form of nanofibers also exhibits strong quantum size effect as evidenced from the energy shift in near-band-edge emission. Tuned photoluminescence behavior was achieved in Eu3+ doped CuAlO2 through the doping of various trivalent and aliovalent ions into the AlO6 octahedra.