| The solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical to electrical energy. It is usually based around an oxide conducting ceramic electrolyte that requires temperatures above 800°C to operate. There are many advantages to lowering this operation temperature such as more gas sealing options and more efficient startup. One of the key limitations is in the transport of ions across the electrolyte. The most common electrolyte material used is Yttria-Stabilized Zirconia (YSZ). The ionic conductivity can be greatly affected by grain boundaries, dislocations, and point defects.; In this study, dislocations were introduced by heavy ion irradiation. Irradiation with Xe+ or Ar+ produced a large number of point defects and dislocations via a mechanism similar to Frank partial dislocation formation. The dislocation density was on the order of 1012/cm2 and the Burgers vector was 1/2<110>. Heat treatment at temperatures from 800-1400°C changed the defect structure, eliminated point defects, and allowed dislocations to react and grow.; Thin films of YSZ were deposited on silicon substrates using pulsed laser deposition (PLD). Films deposited on a metallized substrate were polycrystalline while films deposited directly onto conductive silicon could be epitaxially grown. Ion irradiation caused the film conductivity to drop by a factor of 2-3 due to additional point defects in the film. Heat treatment removed these point defects allowing the conductivity to recover.; A novel method was developed to produce freestanding YSZ membranes without a silicon substrate by using the Focused Ion Beam (FIB). Thick, single-crystal YSZ pieces were thinned using in-situ X-Ray Energy Dispersive Spectroscopy (EDS) for end point detection. The final membranes were single crystal, less than 350nm thick, and pinhole free. IV curves and impedance measurements were made after irradiation and heat treatment. The conductivity showed similar trends to the PLD deposited thin films.; In addition to the ohmic losses from the electrolyte, ion implantation also affected the activation losses of the electrode. Single crystal electrolytes were implanted with various species. The exchange current density improved by an order of magnitude following irradiation with Na+ and Xe+ on the cathode side. |
