Synthesis and characterization of complex perovskite solid solutions.

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(Thesis) Ph.D.
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Materials based on the solid solution of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 ((1-x)PMN-xPT) show some of the best piezoelectric and ferroelectric properties. Although the ferro-/piezoelectric properties are very good, there are drawbacks to this system such as difficulty in preparing pure phase ceramics and low operating temperature range resulting from the low Curie temperatures ( < 130 °C) exhibited by the compositions that show the best piezoelectric properties (x = 0.28-0.35). The (1-x)PMN-xPT ceramics with x = 0.28 - 0.32 were prepared in pure phase using a novel chemical solution method. The ceramics display better piezoelectric properties compared to those prepared by conventional solid state method. To optimize the ceramic properties, the effect of high temperature poling was investigated, and it was found that poling at high temperature degrades the piezoelectric properties due to a electric field induced phase transition. The same solution method was used to fabricate ceramics of (1-x)PMN-xPT with x = 0.07 and 0.10 which exhibit their maximum of permittivity near room temperature. A sintering temperature of 1100 °C/4hrs was required in order to obtain high density, reduce dielectric losses and increase the dielectric permittivity in order to optimize capacitive performance. The solid solution between Pb(Mg1/3Nb2/3)O3 (PMN) and Bi(Zn1/2Ti1/2)O3 (BZT) was investigated for its structure and dielectric behaviour. The addition of BZT to PMN does not change the structure significantly and it remains cubic to the solubility limit of 0.725PMN-0.275BZT. The dielectric properties exhibit an increase in frequency and temperature dispersion with increasing BZT content, indicating an increase in relaxor behaviour. The Pb(Mg1/3Nb2/3)O3-PbTiO3 -Bi(Zn1/2Ti1/2)O3 solid solution has been prepared in order to explore its structure, dielectric, ferroelectric and piezoelectric properties as a function of composition for use in high TC piezoelectric applications. The structure and properties were mapped as a function of composition to establish the ternary phase diagrams of this system for its structure, dielectric and piezo-/ferroelectric properties.
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