Formation mechanism and characteristics of lanthanum-doped BaTiO{sub 3} powders and ceramics prepared by the sol–gel process

Journal Article · Sat Aug 15 00:00:00 EDT 2015 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2015.05.022· OSTI ID:22476134

Ianculescu, Adelina Carmen ^[1]; Crisan, Maria; Raileanu, Malina ^[2]; Vasile, Bogdan Stefan; Calugaru, Mihai ^[1]; Crisan, Dorel; Dragan, Nicolae ^[2]; Curecheriu, Lavinia; Mitoseriu, Liliana ^[3]

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1. Department of Oxide Materials Science and Engineering, Politehnica University of Bucharest, 17 Gh. Polizu, 011061 Bucharest (Romania)
2. Ilie Murgulescu Institute of Physical Chemistry, Romanian Academy, 202 Splaiul Independentei, 060021 Bucharest (Romania)
3. Department of Physics, Al. I. Cuza University of Iasi, Blvd. Carol I 11, 700506 Iasi (Romania)

Pure and lanthanum-doped barium titanate nanopowders described by two different formulae, as Ba{sub 1−x}La{sub x}TiO{sub 3}, for lower La concentrations (0 ≤ x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} for higher La concentration (x = 0.025) were prepared by an alkoxide sol–gel method. Single phase compositions were obtained after annealing at 900 °C for 2 h, in air. The increase of the lanthanum content causes structural and morphological changes in the oxide powders, including the evolution of the unit cell from tetragonal toward a cubic symmetry, the particle size decrease and a higher aggregation tendency. SEM investigations of the ceramics sintered at 1300 °C for 4 h indicate significant changes of the microstructural features (strong decrease of the average grain size and increase of the intergranular porosity) with the raise of La amount. Lanthanum addition to barium titanate prepared by sol–gel induces a more significant shift of the Curie temperature toward lower values, than that one reported in literature for ceramics of similar compositions, but processed by the conventional solid state method. The compositions with smaller La amount (x ≤ 0.005) show semiconducting properties at room temperature and high relative dielectric permittivity values, while the undoped ceramics and those doped with higher La content (x = 0.025) are good dielectrics. The ceramic with x = 0.025 exhibits acceptable low losses, a very diffuse ferroelectric–paraelectric transition and Curie temperature closed to the room temperature, being thus susceptible for high tunability applications. - Highlights: • Ba{sub 1−x}La{sub x}TiO{sub 3} (x ≤ 0.005) and Ba{sub 1−x}La{sub x}Ti{sub 1−x/4}O{sub 3} (x = 0.025) were prepared by sol–gel. • Ceramics with x < 0.5 exhibit semiconductor and high dielectric properties. • Ceramic with x = 0.025 exhibits acceptable low losses and diffuse phase transition.

• OSTI ID: 22476134
• Journal Information: Materials Characterization, Vol. 106; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AGGLOMERATION
BARIUM COMPOUNDS
CERAMICS
CURIE POINT
DOPED MATERIALS
FERROELECTRIC MATERIALS
LANTHANUM ADDITIONS
NANOSTRUCTURES
OXIDES
PARTICLE SIZE
PERMITTIVITY
PHASE TRANSFORMATIONS
POROSITY
SCANNING ELECTRON MICROSCOPY
SEMICONDUCTOR MATERIALS
SOL-GEL PROCESS
SYMMETRY
TEMPERATURE RANGE 0273-0400 K
TITANATES