Patterned Solid State Growth of BaTiO3 Crystals
Open Access
- Author:
- Ugorek, Michael S
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- January 28, 2009
- Committee Members:
- Gary Lynn Messing, Dissertation Advisor/Co-Advisor
Gary Lynn Messing, Committee Chair/Co-Chair
Susan E Trolier Mckinstry, Committee Member
Clive A Randall, Committee Member
Thomas R Shrout, Committee Member - Keywords:
- Barium Titanate
single crystal growth
patterning - Abstract:
- An understanding of microstructure evolution in ceramic materials, including single crystal development and abnormal / enhanced grain growth should enable more controlled final ceramic element structures. In this study, two different approaches were used to control single crystal development in a patterned array. These two methods are: 1) patterned solid state growth in BaTiO3 ceramics, and 2) metal – mediated single crystal growth in BaTiO3. With the patterned solid state growth technique, optical photolithography was used to pattern dopants as well as [001] and [110] BaTiO3 single crystal template arrays with a 1000 micron line pattern array with 1000 micron spacings. These patterns were subsequently used to control the matrix grain growth evolution and single crystal development in BaTiO3. It was shown that the growth kinetics can be controlled by a small initial grain size, atmosphere conditions, and the introduction of a dopant at selective areas / interfaces. By using a PO2 of 1x10-5 atm during high temperature heat treatment, the matrix coarsening has been limited (to roughly 2 times the initial grain size), while retaining single crystal boundary motion up to 0.5 mm during growth for dwell times up to 9 h at 1300oC. The longitudinal and lateral growth rates were optimized at 10 – 15 micron/h at 1300oC in a PO2 of 1x10-5 atm for single crystal growth with limited matrix coarsening. Using these conditions, a patterned microstructure in BaTiO3 was obtained. With the metal – mediated single crystal growth technique, a novel approach for fabricating 2-2 single crystal / polymer composites with a kerf < 5 microns was demonstrated. Surface templated grain growth was used to propagate a single crystal interface into a polycrystalline BaTiO3 or Ba(Zr0.05Ti0.95)O3 matrix with lamellar nickel layers. The grain growth evolution and texture development were studied using both [001] and [110] BaTiO3 single crystals templates. By using a PO2 of 1x10-11 atm during high temperature heat treatment, matrix coarsening was limited while enabling single crystal boundary motion up to 0.35 mm during growth between 1250oC and 1300oC with growth rates ~ 3-4 micron/h for both single crystal orientations. By removing the inner electrodes, 2-2 single crystal (or ceramic) composites were prepared. The piezoelectric and dielectric properties of the composites of the two compositions were measured. The d33 and d31 of the composites were similar to the polycrystalline ceramic of the same composition.