Search results for "Axial pressure"
showing 10 items of 12 documents
Simultaneous Synthesis and Consolidation of Nanostructured MoSi2
2002
A new process combining electric field activation and the imposition of pressure from mechanically activated powder mixtures is demonstrated as a means to simultaneously synthesize and densify nano-MoSi2 in one step. Nanophase reactants (Mo + 2Si) produced by mechanical activation are reacted by field activation with the simultaneous application of a uniaxial pressure. Mo + 2Si powders were comilled in a specially designed planetary mill to obtain nanometric reactants but to avoid formation of any product phases. These were then subjected to high alternating currents (1600 A) and pressures of 106 MPa. Under these conditions, a reaction is initiated and completed within a short period of tim…
Processing, basic characterization and standard dielectric measurements on PLZT x/65/35 (2≤x≤13) ceramics
2016
ABSTRACTThe influence of external stress (0-800bar) on the dielectric properties of PLZT x/65/35 (2≤x≤13) ceramics was investigated. Applying uniaxial pressure leads to a change in the peak intensity of the electric permittivity (ϵ), of its frequency dispersion as well as in the dielectric hysteresis. The peak intensity of ϵ becomes broader and shifts to lower temperatures for PLZT x/65/35 with x = 2, 4, 6, 7, 9.75, 10, 11 and 13, with increasing pressure, on heating. It was concluded that applying uniaxial pressure induces an increase of Tm, and thus has similar effects as the increase of the Ti ion concentration in the PZT system. Results based on nanoregion switching processes under comb…
Uniaxial Pressure Effect on Dielectric Properties of 0.7Na0. 5Bi0.5TiO3‐0.3SrTiO3Ceramics
2014
The 0.7Na0.5Bi0.5TiO3-0.3SrTiO3 ceramics were prepared by a solid-state mixed-oxide technique at 1180°C. X-ray diffraction and Raman spectroscopy studies revealed that the obtained samples possess perovskite structure. The behaviour of the electric permittivity (ɛ) and polarization of these ceramics as a function of uniaxial pressure (0 – 1000 bar) were investigated. Applying pressure shifts and decrease of maximum value of ɛ, a diffuseness of the permittivity characteristics, decrease of the thermal hysteresis and change of the polarization. We discuss our results based on elastic changes in inter-ionic distances in the crystal structure and nanoregions switching processes by pressure. The…
Influence of Axial Pressure on the Electrical Properties of Li0.06Na0.94NbO3 Ceramic
2011
Lead-free ceramic Li0.06Na0.94NbO3 was synthesized using a conventional solid-state processing. The single-phase perovskite structure was identified by X-ray powder diffraction technique. The values of lattice parameters of Li0.06Na0.94NbO3 are lower than those for pure NaNbO3. The EDS analysis shows the fairly homogeneous distribution of all elements throughout the grains. An axial pressure significantly influences electric properties. With increasing pressure the peak intensity in the ϵ(T) curve decreases, the peak becomes diffused and shifts to a lower temperature. The value of tanδ increases with increasing axial pressure and its local maximum shifts towards lower temperatures.
Influence of Electromechanical Fields on Dielectric Properties of PLZT−x/65/35 Ceramics (x = 6 and 7)
2011
High density and transparent PLZT−x/65/35 (x = 6 and 7) ceramics with the average grain size of 5–7 μm was obtained by two−stage hot−pressing technology. The measurements of temperature/frequency dependence of the permittivities of these ceramics under uniaxial pressure (0–100 MPa) applied parallel to the ac electric field have been carried out. It was found that uniaxial pressure significantly influences dielectric properties of these ceramics. With the increase of pressure the maximum intensity in ϵ(T) curve decreases, becomes more diffuse and shifts towards higher temperature, dielectric dispersion decreases and classical ferroelectric seems to change to relaxor one. It was concluded, th…
Performance of Thin-Film Lithium Energy Cells under Uniaxial Pressure
2008
The objective of this study was two-fold. The first objective was to determine if the all-solid-state thin-film lithium energy cells could withstand the minimal 550 kPa uniaxial pressure required for composite manufacturing, which both specimens successfully did. The second objective was to determine the upper boundary uniaxial pressure limit of operation for the all-solid-state thin-film lithium energy cells. The two all-solid- state thin-film lithium energy cells tested in the present study under uniaxial pressure performed well even when subjected to uniaxial pressures up to about 2.0 MPa. However, pressures higher than this value led to their degradation. The observed degradation was du…
Uniaxial Pressure Effects on the Dielectric Properties of the PLZT-x/65/35 (x = 9.75 and 10) Ceramics
2012
The influence of uniaxial pressure (0-1000 bars) applied parallel to the ac electric field on the dielectric properties of PLZT-x/65/35 ceramics (x = 9.75 and 10) was investigated. The results show that the applied stress has a significant influence on the dielectric properties of PLZT ceramics. Applying uniaxial pressure leads to the reduction of the electric permittivity (ϵ) peak and the frequency dispersion. Moreover, the peak of ϵ becomes diffuse and shifts to a higher temperature with increasing pressure. The results show that applying uniaxial pressure induces similar effects as the increase in Ti−ion concentration in the PZT system. We interpreted our results based on the domain swit…
Effect of Electromechanical Loading on the Dielectric Properties of PLZT−x/65/35 Ceramics (x = 8 and 8.5)
2011
The influence of uniaxial pressure (0-800 bars) applied parallel to the ac electric field on the dielectric properties of La−modified lead–zirconate−titanate ceramics with the Zr/Ti ratio of 65/35 was investigated. Applying uniaxial pressure leads to the reduction of the peak intensity of the electric permittivity (ϵ), of the frequency dispersion as well as of the dielectric hysteresis. The peak intensity of ϵ becomes diffuse and shifts with increasing the pressure. Our results show that applying uniaxial pressure induces similar effects as increasing the Ti−ion concentration in PZT system. We interpreted our results based on domain switching processes under the action of combined electrome…
PLZTx/65/35 ceramics (x = 2 and 4) under electromechanical and temperature loading
2010
The effect of uniaxial pressure (0–1000 bars) applied parallel to the ac electric field on dielectric properties of La-modified lead–zirconate–titanate, Pb(Ti,Zr)O3 (PZT), ceramics with Zr/Ti ratio of 65/35 was investigated. The experimental results revealed that applying uniaxial pressure leads to a reduction of the peak intensity of the electric permittivity (e), of the frequency dispersion as well as of the dielectric hysteresis. Moreover, with increasing pressure, the peak intensity of e becomes diffuse and shifts to a higher temperature. It was concluded that applying uniaxial pressure induces similar effects as increasing the Ti–ion concentration in PZT system. The obtained results we…
The structural and dielectric properties of the Na0.96Li0.04NbO3ceramics
2007
Ceramic samples Na0.96Li0.04NbO3 were obtained using ceramic technology. The phase and structural analysis, the microstructure, EDS and EPMA, dielectric and hysteresis loops measurements have been performed. The dielectric and hysteresis loops measurements of Na0.96Li0.04NbO3 have been carried out. The dielectric measurements were performed both without and under axial pressure up to 120 MPa. It was shown that Na0.96Li0.04NbO3 ceramics have orthorhombic symmetry at room temperature and undergo a first order phase transition at a temperature of about 570 K. The axial pressure shifts the phase transition temperature and decreases the hysteresis in field-polarisation and field-strain dependenc…