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Barium strontium titanate (BST) has been targeted as one potential ferroelectric glass–ceramic for high-energy density dielectric materials. Previous testing has shown that the dielectric constant of these materials was as high as 1000 and the dielectric breakdown strength up to 800 kV/cm. This did not, however, result in exceptional energy density (∼0.90 J/cc). In order to increase overall energy density refining agents can be added to the melt, but the nucleation and growth of the ceramic particles can also play a role. Therefore, in this study the crystallization kinetics were studied to more fully understand how BST phase forms so that the optimal energy density could be obtained. It was determined that the activation energy of the crystallization of BST 70/30 glass–ceramic is approximately 430 kJ/mol which is close to the dissociation energy of Si–O bonds. The Avrami parameter was found to be ∼3 meaning that three-dimensional growth is dominant and the mechanism of growth was interface controlled. [ABSTRACT FROM AUTHOR]

The influence of excess PbO on Pb(Mg1/3Nb2/3)O3–35mol% PbTiO3 {001} single crystal growth by seeded polycrystal conversion (SPC) was studied in the range of 0–10 vol% PbO. As in previous studies, additions of PbO increased the boundary mobility significantly, thus facilitating single crystal growth via SPC. Unlike previous studies, single crystals were grown into pore-free matrices, resulting in different crystal growth kinetics (signifying interface reaction controlled as opposed to diffusion controlled). Porosity was shown to decrease single crystal growth rates by a factor of 2. Additionally, it was found that single crystal and matrix grain growth rates are optimized at 1.5 vol% PbO, as opposed to previous work, which showed that 3 vol% PbO was fastest. Increasing PbO content beyond 1.5 vol% results in growth that is independent of liquid fraction for all annealing times. In addition, the matrix grains were faceted and the growth best-fit parabolic kinetics so interface reaction control was deemed the most likely growth mechanism. [ABSTRACT FROM AUTHOR]

The influence of additions of excess PbO to Pb(Mg⅓Nb[sub 2/3])O[sub 3]35 mol% PbTiO[sub 3] (PMN-35PT) on {111} single-crystal growth by seeded polycrystal conversion was studied in the range of 0-5 vol% PbO. PbO volatilization and hence weight loss during annealing was controlled effectively by a doublecrucible type of arrangement. PbO additions increased boundary mobility significantly in PMN-35PT, thus facilitating single-crystal growth by seeded polycrystal conversion (SPC). This is attributed to the formation of a boundary wetting PbO-based liquid phase. The growth process occurs very rapidly initially, after which it slows down. This is presumably due to both a decrease in the driving force for boundary migration because of an increase in matrix grain size, and a transition to lower mobility facets. It is also shown that for a given annealing time, the size of the grown crystal scales with the lateral dimensions of the seed crystal. [ABSTRACT FROM AUTHOR]