Investigations on surface composition and microstructure of sintered barium titanate |
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Authors: | Sanjiv Kumar V S Raju T R N Kutty |
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Affiliation: | (1) National Centre for Compositional Characterization of Materials, Bhabha Atomic Research Centre, ECIL Post, Hyderabad, 500062, India;(2) Materials Research Centre, Indian Institute of Science, Bangalore , 560012, India |
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Abstract: | The paper describes studies on surface atomic composition, microstructure and microarea elemental distribution in sintered
undoped as well as donor or acceptor doped polycrystalline barium titanate ceramics. The specimens examined are derived from
barium titanate powders synthesized by two different wet chemical procedures namely oxalate precursor route and gel-to-crystallite
conversion. The compositional analysis is carried out by backscattering spectrometry (BS) involving 3.05 MeV 16O(α,α)16O resonant scattering while investigations on microstructure and microarea elemental distribution are performed using scanning
electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The specimens prepared by either method
are monophasic; however, their surface atomic composition, microstructural features as well as electrical characteristics
are significantly different. The specimens obtained by oxalate precursor route generally have Ti rich surfaces and exhibit
coarse to fine grained microstructure depending on the nature and extent of doping. The Mn-doped specimens exhibit appreciable
O deficiency. The specimens prepared by gel to crystallite conversion, in contrast, usually have Ba enriched surfaces and
exhibit fine-grained microstructure. EDS measurements show the segregation of acceptors such as Mn, Cu and Zn in the grain
boundaries of oxalate precursor derived ceramics. Further, the relative atomic ratio of Ti to Ba at the sites of segregations
is higher compared to other locations. |
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