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| - In Situ Measurement of Cation Order and DomainGrowth in an Electroceramic
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| - In-situ synchrotron X-ray diffraction is used to study the cation ordering on the octahedral sites of the microwave dielectric ceramic Ba3ZnTa2O9 (BZT). The ordering process involves a complex interplay between domain growth, evolution of the extent of order within a domain and the interconversion of two distinct BZT phases.
- In situ methods are ideally suited for the study of the development of property-criticalstructural features during materials processing. As an example of their potential in the areaof complex oxide electroceramics, here, we apply in situ synchrotron powder diffraction toinvestigate the ordering processes responsible for optimizing the microwave dielectricproperties of the commercial electroceramic barium zinc tantalate. The collection ofsynchrotron diffraction data with high resolution and high intensity during processing hasallowed the growth of cation site order within a domain and the size of the ordered domainsto be separated during the multistage thermal treatment processing used by industry.Domain growth does not commence until the extent of order within a domain is maximized.Analysis of the superstructure intensities with the Avrami equation shows that nucleationis not important in this process. Domain growth then occurs by the curvature-driven Allen−Cahn mechanism. The complex nature of the ordering is confirmed by the coexistence oftwo phases whose temporal evolution divides into two stages according to the two stages ofordering and domain growth mentioned above. The implications of these observations forindustrial processing procedures aimed at reducing the processing time are discussed.
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