| 1. |
- Liu, Jing, et al.
(author)
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Dielectric, piezoelectric, and ferroelectric properties of grain-orientated Bi3.25La0.75Ti3O12 ceramics
- 2007
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 102:10, s. 104107-
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Journal article (peer-reviewed)abstract
- By dynamic forging during Spark Plasma Sintering (SPS), grain-orientated ferroelectric Bi3.25La0.75Ti3O12 (BLT) ceramics were prepared. Their ferroelectric, piezoelectric, and dielectric properties are anisotropic. The textured ceramics parallel and perpendicular to the shear flow directions have similar thermal depoling behaviors. The d(33) piezoelectric coefficient of BLT ceramics gradually reduces up to 350 degrees C; it then drops rapidly. The broadness of the dielectric constant and loss peaks and the existence of d(33) above the permittivity peak, T-m, show that the BLT ceramic has relaxor-like behavior.
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| 2. |
- Eriksson, Mirva, et al.
(author)
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Ferroelectric Domain Structures and Electrical Properties of Fine-Grained Lead-Free Sodium Potassium Niobate Ceramics
- 2011
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In: Journal of The American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 94:10, s. 3391-3396
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Journal article (peer-reviewed)abstract
- Piezoelectric ceramics of the composition Na(0.5)K(0.5)NbO(3) (NKN) with grain sizes in the range of 0.2-1 mu m were fabricated by spark plasma sintering. Ferroelectric domain size decreases with decreasing grain size and non-180 degrees ferroelectric domains walls were still visible in 200 nm sized grains. The Curie point of the ceramics was grain size independent. This suggests that the critical grain size for a single domain single grain structure for NKN is <200 nm. Optimized processing conditions enabled ceramics of high densities (>99.5% theoretical density) to be made at T >= 850 degrees C. For the dense ceramics (grain size >= 350 nm), the room temperature dielectric constant and coercive field increased with decreasing grain size. The remnant polarization was grain size independent. The material sintered at 850 degrees C is a very good candidate for lead-free piezoelectric applications because of its high piezoelectric constant (d(33) = 160 +/- 2 pC/N).
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| 3. |
- Eriksson, Mirva, et al.
(author)
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Low temperature consolidated lead-free ferroelectric niobateceramics with improved electrical properties
- 2010
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In: Journal of Materials Research. - : Elsevier. - 0884-2914 .- 2044-5326. ; 25:2, s. 240-247
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Journal article (peer-reviewed)abstract
- There is a concerted effort to develop lead-free piezoelectric ceramics. ((Na0.5K0.5)NbO3 based ceramics have good electrical properties, and are a potential replacement material for lead zirconate titanate piezoelectric ceramics. In this work a commercial powder based on (Na0.5K0.5)NbO3 with an initial particle size of 260 nm was consolidated by plasma sintering (SPS). To avoid volatilization, high mechanical pressures were used to minimize the densification temperature. It was found that under a uniaxial pressure of 100 MPa, fully densified compacts can be prepared at 850. Ceramics densified at such a low temperature demonstrate an unusually high remanent polarization (30 mC/cm2) and high d33 (146 pC/N). The improved ferroelectric properties are ascribed to the homogeneous, dense, and submicron grained microstructure achieved.
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