Pure, single phase stoichiometric Pb(Fe<sub>0.5</sub>Nb<sub>0.5</sub>)O₃ (PFN) powders were successfully formed by molten salt synthesis using mixture of NaCl and KCI salts. Lower temperatures and shorter times (0.5 hour at 800°C) were needed for single phase PFN formation from molten salts relative to those required for solid-state methods (4 hours at 1000°C). A systematic study indicating the effects of process parameters, such as temperature, time, and amount of flux with respect to starting oxides, on the PFN formation mechanism and its resulting powder characteristics is reported. The particle size increased with increasing synthesis temperature, the rate of increase is greatest above 900°C which is close to the melting point of lead oxide. PFN powders formed by molten salt synthesis were cuboidal, and were free from agglomerates.
The sinterability, microstructure, and dielectric properties of these powders have been studied for the pure form and with the presence of lead oxide or lithium carbonate. The dielectric properties were sensitive to as-sintered density, the type of additive and the amount of additive. For pure PFN, the highest valve of dielectric constant is 12,270 at 1MHz, which is sintered at 1100°C for 13 hours. Ceramics sintered with lead oxide additive exhibited inferior dielectric properties although lead oxide served as a sintering aid to increase the as-sintered density. The dielectric properties of PFN with lithium carbonate sintered at 1000°C were attractive: the dielectric constant was increased to 14,000 at 1MHz and the D.C. conductivity was reduced. This reduction in the D.C. conductivity was interpreted in terms of the substitution of lithium for iron. / Master of Science
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/41931 |
| Date | 07 April 2009 |
| Creators | Chiu, Chienchia |
| Contributors | Materials Engineering, Desu, Seshu B., Spencer, Chester W., Reynolds, William T. Jr. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | vi, 110 leaves, BTD, application/pdf, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
| Relation | OCLC# 23603927, LD5655.V855_1990.C459.pdf |
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