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Title: The electrical and structural properties of lanthanum-doped lead zirconate titanate
Author: Waring, Miles Alexander Thomas
ISNI:       0000 0001 3563 4175
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2006
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The literature shows there is confusion regarding the factors that control the electrical properties and observed lattice response of PLZT. This study aims to characterise the electrical properties and study the lattice response of PLZT to help resolve these issues. Powders with varying compositions were produced by the mixed oxide process. A range of specimen grain sizes was produced by varying the temperature and hold time during pressure-less sintering. Lanthanum affects the grain growth and diffusion rate, changing the grain size, density and reducing the axial ratio. Strain and polarisation hysteresis, d33 , and permittivity with temperature were all measured. Lanthanum increases the d33 value and reduces the Curie temperature and coercive field strength. However, the results show that grain size and axial ratio also alter these properties. The lattice response was determined using neutron diffraction. Specific planes' lattice spacings, in different spatial directions, were measured by re-orientating the specimens relative to the neutron beam. The spacing of these planes was found to vary with applied field, as a result of the converse-piezoelectric effect, and clastic misfit strains resulting from domain reorientation in surrounding grains. Lattice strain in the nonpolar direction larger than that in the polar direction was observed, along with a small tensile lattice strain in the polar direction after poling. The large strain in the non-polar direction is attributed to elastic misfit strains, but an additional voltageinduced strain was found in that direction, potentially a result of the elastic misfit strain distorting the lattice and allowing the polarisation to align with the field. The tensile poling strain result is explained by a change in the crystal structure, or by considering elastic misfit strains between neighbouring domains. This study has discussed the factors affecting the macroscopic piezoelectric properties, and contributed to the understanding of the underlying lattice response. Supplied by The British Library - 'The world's knowledge'
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available