| 1. |
- Frantti, J, et al.
(author)
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Raman scattering study of the Pb(HfxTi1-x)O-3 ceramics
- 2005
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In: Journal of Electroceramics. - 1573-8663 .- 1385-3449. ; 13, s. 299-303
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Journal article (peer-reviewed)abstract
- Raman spectroscopy was used to study the long wavelength vibrations of tetragonal perovskite (space group P4mm) Pb(HfxTi1-x)O-3 (PHT) (0.10 less than or equal to x less than or equal to 0.50) samples at room temperature and at approximate to 20 K. For x less than or equal to 0.40, Raman spectra collected from the PHT samples were very similar to the previous spectra collected from the PZT samples with the same value of x, except the mode at around 190 cm(-1) whose frequency was decreasing with increasing x in PHT ceramics. Correspondingly, the latter feature was taken as a sign of the 'mass effect' (Hf versus Zr) while the similarity of the remaining parts of the Raman spectra was assumed to be due to the almost identical ionic radii difference between Ti4+ and Zr4+ and between Ti4+ and Hf4+ ionic radii. The behaviour of the mode at around 280 cm(-1) revealed that a phase transition occurred once x was changing from 0.40 to 0.50.
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| 2. |
- Hoffmann, Stefan, et al.
(author)
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Melt synthesis of Al2TiO5 containing composites and reinvestigation of the phase diagram Al2O3-TiO2 by powder X-ray diffraction
- 2006
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In: Journal of Electroceramics. - 1573-8663 .- 1385-3449. ; 16:4, s. 327-330
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Conference paper (peer-reviewed)abstract
- Recently the fabrication of ceramics starting from the appropriate melts of the educts has attracted increasing attention due to the easy shaping of work pieces and other advantages compared to powder sintering methods. We focused our interest on aluminum titanate (beta-Al2TiO5) based ceramics which are interesting for high temperature applications due to the low thermal expansion coefficient. For this purpose we have investigated the titania-rich side of the Al2O3-TiO2 system (up to 50 mol% titania) under rapid cooling conditions with respect to the phase formation. By powder X-ray diffraction we could prove the solely formation of the known phases rutile and beta-Al2TiO5 in agreement with the equilibrium phase diagram. Furthermore, powder pattern fitting has revealed the formation of solid solutions for both compounds.
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| 3. |
- Hu, Qi, et al.
(author)
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Preparation and dielectric properties of La doped NBCCTO ceramics
- 2022
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In: Journal of Electroceramics. - : Springer Nature. - 1385-3449 .- 1573-8663. ; 48:3, s. 117-126
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Journal article (peer-reviewed)abstract
- CaCu3Ti4O12 ceramics have great dielectric constant, excellent temperature stability and good frequency stability. However, due to high dielectric loss, its practical application in engineering is hindered. In this paper, Na0.25Bi0.25LaxCa0.5-3x/2Cu3Ti4O12 (NBLCCTO) ceramics were prepared by solid phase synthesis. The effects of sintering temperature and La content on dielectric properties of NBLCCTO ceramics were studied. The results show when the sintering temperature is 1030celcius and La content is 0.05, NBLCCTO ceramics show better dielectric properties. Its dielectric constant has epsilon(r) = 22,231 at 1 kHz and its dielectric loss is 0.0546 at 10 kHz. Appropriate doping of La can lead to grain refinement and enlarge specific surface area of grain boundary, thus increasing resistivity and reducing dielectric loss. Therefore, NBLCCTO ceramics have lower dielectric loss than Na0.25Bi0.25Ca0.5Cu3Ti4O12 (NBCCTO).
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| 4. |
- Klein, Andreas, et al.
(author)
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The Fermi energy as common parameter to describe charge compensation mechanisms: A path to Fermi level engineering of oxide electroceramics
- 2023
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In: Journal of Electroceramics. - 1573-8663 .- 1385-3449. ; 51
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Journal article (peer-reviewed)abstract
- Chemical substitution, which can be iso- or heterovalent, is the primary strategy to tailor material properties. There are various ways how a material can react to substitution. Isovalent substitution changes the density of states while heterovalent substitution, i.e. doping, can induce electronic compensation, ionic compensation, valence changes of cations or anions, or result in the segregation or neutralization of the dopant. While all these can, in principle, occur simultaneously, it is often desirable to select a certain mechanism in order to determine material properties. Being able to predict and control the individual compensation mechanism should therefore be a key target of materials science. This contribution outlines the perspective that this could be achieved by taking the Fermi energy as a common descriptor for the different compensation mechanisms. This generalization becomes possible since the formation enthalpies of the defects involved in the various compensation mechanisms do all depend on the Fermi energy. In order to control material properties, it is then necessary to adjust the formation enthalpies and charge transition levels of the involved defects. Understanding how these depend on material composition will open up a new path for the design of materials by Fermi level engineering.
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| 5. |
- Liu, J. -M., et al.
(author)
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Ferroelectric and magnetoelectric behaviors of multiferroic BiFeO3 and piezoelectric-magnetostrictive composites
- 2008
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In: Journal of Electroceramics. - : Springer Verlag (Germany). - 1385-3449 .- 1573-8663. ; 21:1-4, s. 78-84
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Journal article (peer-reviewed)abstract
- In this paper we overview our recent work on ferroelectric and magnetoelectric coupling behaviors of multiferroic doped BiFeO3 (BFO) and piezoelectric-magnetostrictive composites. Using rapid liquid sintering method we prepare single-phase BFO ceramics of excellent ferroelectric property. The BFO thin films on Pt-coated silicon wafers by pulsed laser deposition show large remnant polarization but serious ferroelectric switching fatigue. A series of piezoelectric-magnetostrictive composite structures in bulk and thin film forms are prepared and giant magnetoelectric coupling effect of them is observed. The experimentally measured results are confirmed by numerical modeling based on piezoelectric and magnetostrictive constitution equations.
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| 6. |
- Tamraoui, Y., et al.
(author)
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On the structural phase transitions and optical properties of Sr2Sr1-xCaxTeO6 (0 <= x <= 1) ceramics
- 2021
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In: Journal of Electroceramics. - : Springer Nature. - 1385-3449 .- 1573-8663. ; 46, s. 1-13
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Journal article (peer-reviewed)abstract
- A series of double-perovskite oxides Sr2Sr1-xCaxTeO6 (0 <= x <= 1) samples have been prepared in order to study the effect of composition on phase formation and the related optical properties. The objective of this work is to study the possibility of calcium insertion with different percentages since calcium in known to enhance the electrical properties. In this work a well detailed structure and phase transitions investigation of the compounds were conducted and probed by X-ray diffraction and Raman spectroscopy techniques at room temperature. Both Rietveld refinements and Raman studies revealed that two phase transitions took place as the calcium amount x increases; a first from a triclinic to a hexagonal in the range 0.1 < x < 0.25 and a second from the hexagonal to a monoclinic structure in the range 0.5 < x < 0.6. The optical absorption alpha(lambda) was also determined as a function of calcium content in the series samples using UV-vis analysis. It was revealed that a remarkable change occured in the cut-off wavelength, confirming the sequence of phase transitions C1 -> R (3) over bar m -> P2(1)/n. The optical band gap measurements showed that the triclinic Sr3TeO6 and the monoclinic Sr2CaTeO6 phases have band gap values of 2.75 and 2.81 eV, respectively. When the calcium increased to x = 0.25 (Sr2.75Ca0.25TeO6)(,) remarkable decrease of the band gap value was observed, with Eg = 2.627 eV.
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| 7. |
- Tazawa, Masato, et al.
(author)
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Optical constants of vacuum evaporated SiO film and an application
- 2006
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In: Journal of Electroceramics. - : Springer Science and Business Media LLC. - 1385-3449 .- 1573-8663. ; 16:4, s. 511-515
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Journal article (peer-reviewed)abstract
- Silicon monoxide films were deposited on silver films on glass substrates and studied by infrared ellipsometry to determine the optical properties in the infrared wavelength range from 1.3 to 40 micrometers. The thicknesses of silicon monoxide and aluminum films were designed to 1 micrometer and 200 nanometers, respectively. The ellipsometric measurements were carried out by using a spectro-ellipsometer attached with an FT-IR. The imaginary part of the refractive index shows a high absorption region which is centered at 10 micrometers, whereas in other wavelength regions it shows rather low absorption. The resultant optical properties of silicon monoxide film are compared with published data. As an application, the spectral reflectance of spectral selective panel heating surface is calculated.
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| 8. |
- Bexell, M, et al.
(author)
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Microassembly of a piezoelectric miniature motor
- 1999
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In: JOURNAL OF ELECTROCERAMICS. - : KLUWER ACADEMIC PUBL. - 1385-3449. ; 3:1, s. 73-83
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Journal article (other academic/artistic)abstract
- An assembly method for the fabrication of a piezoelectric miniature motor is presented. The fabrication is done by placement and soldering of piezoceramic elements onto a silicon substrate. The assembly of the miniature motor demands high precision (+/-5
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