Effect of residual phosphorus left by phosphate ester on BaTiO{sub 3} ceramics

Journal Article · Sat Feb 01 04:00:00 EST 1997 · Materials Research Bulletin

DOI:https://doi.org/10.1016/S0025-5408(96)00179-1· OSTI ID:455243

Caballero, A C ^[1]; Fernandez, J F; Moure, C; Duran, P ^[2]

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1. Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Materials Science and Engineering
2. CSIC, Madrid (Spain). Electroceramics Dept.

Phosphate ester used as a dispersant for BaTiO{sub 3} tape-casting slips leaves a certain amount of residual phosphorus which modifies the sintering behavior microstructure, and electrical properties of the sintered ceramic. Dilatometric measurements together with SEM and TEM study of the microstructure revealed that residual phosphorus located at the surfaces of the BaTiO{sub 3} particles inhibits grain growth during the first sintering stage. High density materials with homogeneous fine-grained microstructure were sintered below 1,300 C. Higher sintering temperatures led to grain growth and Ba{sub 3}(PO{sub 4}){sub 2} second phase was formed. For the samples with a homogeneous fine-grained microstructure, permittivity values as high as 4,000 were measured, while dielectric losses were around one order of magnitude lower than those for the phosphorus-free material. On the other hand, when second phase was observed, a marked increase of the dielectric losses was detected. Based on the microstructure characteristics of the samples and the analysis of the grain boundary conductivity by complex impedance spectroscopy, it is proposed that changes in the local concentration of P{sup 5+} at the grain boundaries are responsible for the change of the grain boundary conductivity. The charge compensation mechanism would change from cation vacancy to Ti{sup 3+} formation depending on the local P{sup 5+} concentration at the grain boundaries.

• OSTI ID: 455243
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 2 Vol. 32; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
BARIUM PHOSPHATES
ELECTRICAL PROPERTIES
EXPERIMENTAL DATA
GRAIN BOUNDARIES
GRAIN GROWTH
IMPURITIES
MICROSTRUCTURE
PERMITTIVITY
PHOSPHORUS
SINTERING
TITANIUM OXIDES