High pressure FAST of nanocrystalline barium titanate

Journal Article · Wed Jun 01 00:00:00 EDT 2016 · Ceramics International

DOI:https://doi.org/10.1016/j.ceramint.2016.05.193· OSTI ID:1341402

Fraga, Martin B. ^[1]; Delplanque, Jean -Pierre ^[1]; Yang, Nancy ^[2]; Lavernia, Enrique J. ^[3]; Monson, Todd C. ^[4]

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1. Univ. of California, Davis, CA (United States)
2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
3. Univ. of California, Irvine, CA (United States)
4. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Here, this work studies the microstructural evolution of nanocrystalline (<1 µm) barium titanate (BaTiO₃), and presents high pressure in field-assisted sintering (FAST) as a robust methodology to obtain >100 nm BaTiO₃ compacts. Using FAST, two commercial ~50 nm powders were consolidated into compacts of varying densities and grain sizes. Microstructural inhomogeneities were investigated for each case, and an interpretation is developed using a modified Monte Carlo Potts (MCP) simulation. Two recurrent microstructural inhomogeneities are highlighted, heterogeneous grain growth and low-density regions, both ubiqutously present in all samples to varying degrees. In the worst cases, HGG presents an area coverage of 52%. Because HGG is sporadic but homogenous throughout a sample, the catalyst (e.g., the local segregation of species) must be, correspondingly, distributed in a homogenous manner. MCP demonstrates that in such a case, a large distance between nucleating abnormal grains is required—otherwise abnormal grains prematurely impinge on each other, and their size is not distinguishable from that of normal grains. Compacts sintered with a pressure of 300 MPa and temperatures of 900 °C, were 99.5% dense and had a grain size of 90±24 nm. These are unprecedented results for commercial BaTiO₃ powders or any starting powder of 50 nm particle size—other authors have used 16 nm lab-produced powder to obtain similar results.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
• Sponsoring Organization: AFRL; USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000; AC04–94AL85000
• OSTI ID: 1341402
• Alternate ID(s): OSTI ID: 1325373
• Report Number(s): SAND-2016-12477J; PII: S0272884216308136
• Journal Information: Ceramics International, Vol. 42, Issue 12; ISSN 0272-8842
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
barium titanate
sintering
grain size
Spark plasma sintering