The mechanism of abnormal grain growth in Sr{sub 0.6}Ba{sub 0.4}Nb{sub 2}O{sub 6} ceramics
- Materials Science Centre, University of Manchester/UMIST, Grosvenor St. Manchester, M1 7HS (United Kingdom)
Strontium barium niobate, Sr{sub 0.6}Ba{sub 0.4}Nb{sub 2}O{sub 6} (SBN40) ceramics were prepared by the mixed oxide route; specimens sintered at 1300{degree}C{endash}1450{degree}C for 2{endash}4 h had densities of {approximately}95{percent} theoretical. The use of {open_quotes}conventional{close_quote}{close_quote} conditions (1300{degree}C; {approximately}200{degree}C below the melting temperature) gave rise to a duplex structure comprising a mixture of small grains and abnormally large grains (in excess of 100 {mu}m). Transmission electron microscopy studies revealed a Nb-rich, Ba-poor phase at the grain boundaries; the low melting temperature of this phase caused localized liquid phase sintering, resulting in abnormal grain growth. Dual-stage sintering (sintering at 1250{degree}C for 4 h, followed by sintering at a temperature in the range 1350{degree}C{endash}1450{degree}C) inhibited abnormal grain growth. The use of a fast heating rate (600{degree}C/h) and dual-stage sintering (1250{degree}C and 1450{degree}C) yielded samples with good transparency and preferential orientation along the c-direction of the tetragonal unit cell. The dielectric properties depended sensitively on microstructure. Specimens with the highest densities had the highest relative permittivities (2400{endash}2750); specimens with more uniform distribution of grain sizes had sharper dielectric maxima. A mechanism for abnormal grain growth is proposed. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 459823
- Journal Information:
- Journal of Applied Physics, Vol. 81, Issue 1; Other Information: PBD: Jan 1997
- Country of Publication:
- United States
- Language:
- English
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