| 1. |
- Abadei, S., et al.
(författare)
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DC field dependent properties of Na0.5 K0.5 NbO3/SiO2/Si structures at millimeter-wave frequencies
- 2001
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:13, s. 1900-1902
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Tidskriftsartikel (refereegranskat)abstract
- Dielectric properties of laser-ablated 0.5-μm-thick c-axis epitaxial Na0.5K0.5NbO3 films on high-resistivity (7.7 Ω cm) silicon SiO2/Si substrate are studied experimentally at frequencies up to 40 GHz. For measurements, planar 0.5-μm-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of Na0.5K0.5NbO3 films. The slot width between the electrodes is 2 or 4 μm. 13% capacitance change at 40 V dc bias and Q factor more than 15 are observed at 40 GHz, which makes the structure useful for applications in electrically tunable millimeter-wave devices
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| 2. |
- Babushkin, O., et al.
(författare)
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Diffusionless phase transition in the ZrO2-TiO2 system
- 1994
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Ingår i: Solid-solid phase transformations. - Warrendale, Pa. : Minerals, Metals & Materials Society. - 0873392787 ; , s. 743-748
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Konferensbidrag (refereegranskat)abstract
- Stable and metastable phase relationships in the ZrO2-TiO2 system were investigated using homogeneous samples with ZrO2 particles of different surface area. Phase analysis associated with the diffusionless and reversible monoclinic-tetragonal transition has been performed with high temperature X-ray diffractometry. The rate of the phase transition, depending on powder morphology, is presented. The character of the hysteresis loop associated with the martensitic phase change for pure ZrO2 and for the ZrO2-TiO2 system is discussed
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| 3. |
- Babushkin, Oleg, et al.
(författare)
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Effect of sintering atmosphere and alumna precursors on the sequence of solid state reactions i the AlN-Y2O3-Al2O3 system
- 1993
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Ingår i: Third Euro-ceramics conference. - : Faenza Editrice Iberica. - 8487683053 ; , s. 1079-1084
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Konferensbidrag (refereegranskat)abstract
- High temperature x-ray diffraction was used to investigate the evolution of phases at 1050 C in three AlN-based ceramic powder mixtures containing Al2O3 and Y2O3 additives. The overall composition was 87.5 mol% AlN, 10% Al2O3 and Y2O3 2.5%; the alumina precursors in the three mixtures were Al2O3, AlCl3 and Al(NO3)3 respectively. The effects of the tape of precursor and the heat treatment atmosphere (vacuum or nitrogen) on the phases formed and the sequence of their formation over a period of two hours, are presented and discussed.
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| 4. |
- Babushkin, O., et al.
(författare)
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High-temperature graphite furnace for X-ray powder diffraction
- 1993
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Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 4:8, s. 816-819
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Tidskriftsartikel (refereegranskat)abstract
- A modified computer-controlled high-temperature x-ray diffractometer with good stability and an upper temperature limit of more than 2300 K is described. A critical test of the system, determining the thermal expansion of Pt, Ni and AlN, showed close agreement with dilatometric and literature data. Lattice thermal expansion data of CrB2 and TiB2 up to 2100 K were also determined
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| 5. |
- Babushkin, O., et al.
(författare)
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Kinetic Aspects of the Formation of Lead Zirconium Titanate
- 1996
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 16:12, s. 1293-1998
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics of the second calcination step in the formation of PZT solid solution (with perovskite ABO3 lattice) has been investigated by using two different particle sizes of the B-site precursor (1·91 and 5·08 μm), the finer size being obtained by prolonged milling. In-situ analysis performed by high-temperature X-ray diffractometry in a non-isothermal mode (20-800°C) revealed a reduction of the calcination temperature by 100°C with a decrease in particle size of the precursor. In order to clarify the mechanism of the solid-state reaction to PZT, isothermal heat treatment of the mixtures was performed in the temperature range 540-700°C. The activation energies for the fine and the coarse powders were estimated as 150 and 210 kJ mol 1 respectively, and the reaction was found to follow the Jander model for diffusion-controlled solid-state reaction kinetics
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| 6. |
- Babushkin, O., et al.
(författare)
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Morphological effect of Al2O3 additives on sinterability of wear-resistant AlN ceramics
- 1990
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Ingår i: Structural ceramics processing, microstructure and properties. - Roskilde : Risø National Laboratory. - 8755016626 ; , s. 175-180
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Konferensbidrag (refereegranskat)abstract
- In the present study on AlN-based ceramic materials, an attempt was made to show the morphological influence of the precursors on the phase relationships during sintering as well as the microstructural development of the material. An investigation has been done of the phase transformations during pressureless sintering of wear-resistant ceramics based on the AlN-Al2O3-Y2O3 system in the AlN-rich field as well as a study of the effect of different precursors, such as Al2O3, AlCl3 and Al(NO3)3, on the sequence of phase transitions in the low temperature field (800-1400°C). The peculiarities of phase transitions in dynamic and isothermal schedules have also been discussed.
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| 7. |
- Babushkin, O., et al.
(författare)
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PZT phase formation monitored by high-temperature X-ray diffractometry
- 1997
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Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 17:6, s. 813-818
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Tidskriftsartikel (refereegranskat)abstract
- The crystallisation kinetics of amorphous sol-gel PZT thin films were investigated using high-temperature X-ray diffraction. Crystallisation for different isotherms was monitored as a function of time. Phase transformation data were obtained from integrated X-ray peak intensities which were calibrated based on image analysis of the surface microstructure of the samples at the end of the isothermal treatments. An activation energy of 310 kJ/mol was obtained without assuming a specific kinetic model. From the transformation data, a TTT diagram was constructed for the ranges studied.
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| 8. |
- Babushkin, Oleg, et al.
(författare)
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Reaction sequence in the formation of perovskite Pb(Zro0.48Ti0.52)O3-Pb(Nb2/3Ni1/3)O3 solid solution : Dynamic heat-treatment
- 1998
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Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 18:7, s. 737-744
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Tidskriftsartikel (refereegranskat)abstract
- The sequence of the solid state reactions in the PbOZrO 2-TiO2-Nb2O5-NiO system has been investigated. The oxide mixing route utilised in sample preparation was selected in order to determine the basic reaction path in the formation of the PZTPNN perovskite phase. It has been established that the main intermediate phases formed prior to PZTPNN are PbTiO3 and pyrochlore Pb-Nb-based phases. The sequence in the pyrochlore formation was from tetragonal Pb3Nb2O8 (500 °C) to rhombohedral Pb2Nb2O7 (600-750 °C) and finally to cubic Pb3Nb4O13 (650-850 °C). The formation of the perovskite phase proceeded from mutual solubility of PbTiO3 and pyrochlore Pb3Nb4O13 phases, accompanied by dissolving of residuals (PbZrO3 and NiO) in the perovskite solid solution formed
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| 9. |
- Babushkin, Oleg, et al.
(författare)
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Thermal expansion of hot isostatically pressed hydroxyapatite
- 1994
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Ingår i: Journal of Materials Chemistry. - 0959-9428 .- 1364-5501. ; 4:3, s. 413-415
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Tidskriftsartikel (refereegranskat)abstract
- A dense and transparent hydroxyapatite produced by hot isostatic pressing was investigated with respect to its stability and thermal expansion behaviour in the range 20–1150 °C. The evaluation was made by high-temperature X-ray diffraction in a reconstructed test chamber with a BN sample holder and Pt as an internal (in situ) reference. No degradation of the hydroxyapatite was detected in the range investigated. The lattice parameters, a and c, were determined as a function of temperature. The linear thermal expansion coefficient, determined by dilatometry, was 17.1 × 10–6°C–1, which agreed well with the value 17.3 × 10–6°C–1 obtained by X-ray diffraction.
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| 10. |
- Bartek, A., et al.
(författare)
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Fabrication of silicon nitride/oxynitride by reaction bonding and post sintering
- 1992
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Ingår i: 4th International Symposium on Ceramic Materials and Components for Engines. - London : Elsevier. - 1851667768 ; , s. 625-632
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Konferensbidrag (refereegranskat)abstract
- Reaction bonding and post sintering of silicon nitride/oxynitride was investigated as a route to fabricate a material with good oxidation resistance and good high temperature strength. Silicon powders, mixed with 0, 2, 4, 8 and 16 wt% silica, were CIPed at 150 MPa and nitrided using the nitrogen demand principle. Four different nitriding gas compositions were used, consisting of different amounts of hydrogen, argon and helium mixed with nitrogen. Post sintering at atmospheric pressure and by HIP at 160 MPa were investigated to densify the materials. Samples were characterised by XRD, SEM and Hg-porosimetry in both the nitrided and sintered state
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