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1.
We fabricate Sm-doped Ca3Co4O9+δ(CCO)bulk materials in magnetic field during both processes of chemical synthesis and cold pressing.The structure and electrical performance of the samples are investigated.With the increasing Sm concentration,the electrical conductivity 1/ρ decreases and the Seebeck coefficientαincreases.As a result,the power factor(PF=α^2/ρ)is raised slightly.After applying magnetic field,the extent of texture,grain size and density of all the bulk materials are improved obviously,thereby an enhanced electrical conductivity can be gained.Additionally,the degeneracy of Co^4+ state in the CoO2 layer of CCO is also increased as the magnetic field is used in the preparing process,which results in an enhancedα.The Ca2.85Sm0.15Co4O9+δ prepared in magnetic field shows the largest power factor(0.20 mW·m^-1·K^-2 at 1073 K). 相似文献
2.
《Current Applied Physics》2009,9(1):268-273
Ceramic compositions of a combination between lead magnesium niobate, Pb(Mg1/3Nb2/3)O3, and lead titanate, PbTiO3, were fabricated by using Mg4Nb2O9 precursor technique. Their electrical properties with respect to temperature and frequency were examined and the effect of sintering conditions on phase formation, densification, microstructure and electrical properties of the ceramics were examined. It has been found that optimisation of sintering condition can lead to a highly dense and pyrochlore-free PMN–PT ceramics. The gradual decreasing of the physical properties of the sintered ceramics was related to the gradual decrease of density and inhomogeneous microstructure. The results also revealed that for the lower concentration of lead titanate a relaxor behavior is noticed with a high electrostrictive effect, which was almost hysteretic free. However, higher amount of lead titanate led to a normal ferroelectric behavior. 相似文献
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Raed Jaradat Mohammed S. Abu-Jafar Issam Abdelraziq Diana Dahliah Rabah Khenata 《Chinese Journal of Physics (Taipei)》2018,56(3):830-843
The calculation of the structural, mechanical and thermodynamic properties of the alkali hydrides XH (X?=?K, Rb and Cs) in rock-salt (RS), cesium chloride (CsCl), zinc-blende (ZB) and wurtzite (WZ) phases are done by using the full-potential linearized augmented plane wave (FP-LAPW) method within the frame work of the density functional theory (DFT) as implemented in the WIEN2K code. The Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) was used for the exchange-correlation potential.The elastic constants and their related properties, as well as the thermodynamic properties, were obtained by using the IRelast package. The calculated elastic constants for the alkali hydrides, with the four structures RS, CsCl, ZB and WZ, at ambient pressure are mechanically stable. The elastic constants and their related properties in the RS structure are changeable with increasing pressure. Elastic constants, bulk modulus, shear modulus (stiffness) and Debye temperatures of these compounds are decreased as going from K to Cs in the periodic table. These compounds in the RS structure are mechanically stronger at ambient conditions. 相似文献
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《Solid State Communications》1986,58(8):545-549
Binary semiconducting glasses of xV2O5·(1−x)B2O3 system with x ranging from 0.6 to 0.9 have been investigated to elucidate their electronic conduction. The values of conductivity and activation energy of these glasses are in good agreement with previous results on most V2O5-based glasses. Arguments for the small-polaron as the charge carrier in V2O5B2O3 glasses are presented. 相似文献
6.
H.Q. Liu Y. Song S.N. Zhang X.B. Zhao F.P. Wang 《Journal of Physics and Chemistry of Solids》2009,70(3-4):600-603
The Ca3?xYxCo4O9+δ (x=0, 0.15, 0.3) ceramics were prepared by combining the polyacrylamide gel method and the spark plasma sinter (SPS) technology in order to improve the thermoelectric properties of Ca3Co4O9+δ ceramics. The Seebeck coefficients and the resistivities of the Y-doped samples were obviously enhanced due to the decrease of carrier concentration, and their thermal conductivities were decreased due to the impurity scattering effect. The thermoelectric properties were improved at high temperature by Y-doping according to the power factor analysis and the thermoelectric figure of merit (ZT) data. The optimized figure of merit ZT=0.22 at 973 K was obtained for Ca2.7Y0.3Co4O9+δ. 相似文献
7.
《Current Applied Physics》2009,9(1):249-252
Effects of compressive stress on the ferroelectric properties of ceramics in PZT–PZN system were investigated. The ceramics with a formula (1−x)Pb(Zr1/2Ti1/2)O3–xPb(Zn1/3Nb2/3)O3 or (1−x)PZT–(x)PZN (x = 0.1–0.5) were prepared by a conventional mixed-oxide method. The ferroelectric properties under the compressive stress of the PZT–PZN ceramics were observed at the stress levels up to 170 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization (Psat), the remnant polarization (Pr), and the coercive field (Ec) decreased. These results were interpreted through the non-180° ferroelastic domain switching processes. 相似文献
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Gold-197 Mössbauer spectroscopy has been used to investigate the MAu system (M=K, Kb, Cs). Of the 11 alloys RbAu and CsAu give Mössbauer spectra consistent with cubic gold environments, while (2,2,2-crypt M) Au, (M=K, Pb, Cs) all have cubic gold environments. Comparison of the isomer shifts for the crypted and uncrypted salts leads to the conclusion that in RbAu and CsAu considerable electron density is removed from the gold 5d orbitals. 相似文献
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S. N. Kallaev A. R. Bilalov R. M. Ferzilaev Z. M. Omarov K. Bormanis S. M. Sadykov 《Physics of the Solid State》2012,54(9):1829-1831
The temperature dependences of the permittivity and specific heat of a mixed (1 ? x)PbNi1/3Nb2/3O3-xPbTiO3 system (where x = 0.3, 0.4, 0.5) have been studied over a wide temperature range 290?C700 K. It has been shown that the composition with x = 0.3 undergoes a diffuse phase transition at T m ?? 315 K. A specific heat anomaly that is characteristic of the phase transition has been revealed at T ?? 315 K in all the compositions under study. 相似文献
10.
Mirzadeh M. Akhavan M. 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,43(3):305-318
We have studied the structural, electrical, and magnetic properties of the
normal and superconducting states Gd(Ba2-xLax)Cu3O7+
[Gd(BaLa)123] samples with 0.0 x 0.8 prepared by the
standard solid-state reaction. XRD characterization shows an
orthorhombic-tetragonal structural transition at x=0.2. Iodometric titration
analysis shows the oxygen content of the samples increase with the increase
of La doping. The resistivity curves show that for x0.15, there is
metallic behavior, and for x0.2, there is a gradual insulating
transition behavior in the normal state. The metal-insulator and
superconductor-insulator transitions occur between x=0.35 and x=0.4. The
superconducting transition temperature decreases with the increase of La
content as two-step curve. The normal-state resistivity is fitted for two
and three dimensional variable range hopping (2D&3D-VRH) and Coulomb gap
(CG) regimes, separately. The results show that the dominant mechanism is CG
for x0.35, and VRH for x0.4. The pinning energy U, derived from
the thermally activated flux creep (TAFC) model and Ambegaokar-Halperin (AH)
theory, shows a power-law relation as UH -. The
critical current density decreases with the increase of La doping and
magnetic field. The E-J curves show that the induced electric field
increases with the increase of magnetic field and La concentration. The
magnetization measurements indicate that the critical penetration fields and
magnetic current density decrease with La doping. 相似文献
11.
采用Rb2 CO3 ,Cs2 CO3 ,H3 BO3 和CaCl2 合成了新的硼氧酸盐复盐Rb2 Ca[B4O5(OH) 4 ]2 ·8H2 O和Cs2 Ca[B4O5(OH) 4 ]2 ·8H2 O ,通过化学分析和热分析等确定了化学物的组成。给出了两种化合物的FTIR光谱和Ra man光谱 ,分析了各种谱线的归属。 相似文献
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Eu~(3 )的发光是人们所熟悉的。主要地从~5D_0能级起源,跃迁到~7F_J簇。在Eu~(3 )的发射光谱中,一般地是~5D_0-~7F_2或~5D_0-~7F_1谱线占优势。如果Eu~(3 )离子占有一个位置,该位置的对称允许是线性晶体场项,则~5D_0-~7F_0跃迁仅仅具有可以测量的强度。本工作涉及在AMgF_3(A=K,Rb,Cs)晶格中~5D_0能级的位置。这种位置是由在这些晶格中具有适当强度的~5D_0-~7F_0发光跃迁得来的。 相似文献
14.
We report here the synthesis of layered perovskite oxides of the composition La0.5Sr1.5Ti0.5Cr0.5O4 and LaSr2TiCrO7 by conventional solid-state reaction method. Results of XRD analysis show that the phases crystallize with tetragonal unit cell in the space group I4/mmm. Both phases behave as insulators and the linearity of log ρ versus T ?1/4 plot in the temperature range 150–350 K suggests that the electronic conduction occurs by Mott’s variable range hopping mechanism. The antiferromagnetic interactions observed for the samples arise from Cr3+–O–Cr3+ superexchange interaction. 相似文献
15.
Jiagang Wu Sha Qiao Jianguo Zhu Dingquan Xiao 《Applied Physics A: Materials Science & Processing》2012,109(2):273-277
0.852[Bi1/2(Na1?x Li x )1/2]TiO3?C0.110(Bi1/2K1/2)TiO3?C0.038Ba0.85Ca0.15Ti0.90Zr0.10O3 (BNLT?CBKT?CBCTZ-x) new ternary piezoelectric ceramics were fabricated by the conventional solid-state method, and their piezoelectric properties as a function of the Li content were mainly investigated. A?stable solid solution with a single perovskite structure has been formed, and the depolarization temperature (T d) of these ceramics was identified by using the temperature dependence of the dielectric loss. The T d value of these ceramics gradually decreases, while the T m value increases with increasing the Li content. The dielectric constant increases and the dielectric loss decreases with increasing the Li content, and an enhanced piezoelectric behavior of d 33??223 pC/N and k p??35.2?% has been demonstrated in these ceramics with x=0.06. 相似文献
16.
《Current Applied Physics》2009,9(4):802-806
The influences of Zr/Ti ratio on electrical properties of the 0.8Pb(ZrxTi1−x)O3–0.2Pb(Co1/3Nb2/3)O3 ceramics prepared by a mixed-oxide method (with x = 0.46, 0.48, 0.50, 0.52, and 0.54) have been investigated in order to identify the morphotropic phase boundary composition in this system. With XRD analysis, the crystal structure of dense specimens appeared to change gradually from tetragonal to rhombohedral with increasing Zr content. The dielectric properties measurements showed a maximum dielectric constant at x = 0.50, while the transition temperature decreased with increasing Zr content in the system. Moreover, all ceramics showed diffused phase transition behaviors with a minimum diffusivity at x = 0.50. In addition, the Polarization–Electric field (P–E) hysteresis loops of the ceramic systems also changed significantly with the Zr content. Interestingly, the loop squareness parameter reached maximum around x = 0.50. Other ferroelectric hysteresis parameters showed noticeable change at x = 0.50. These results clearly showed the significance of Zr/Ti ratio in controlling the electrical properties of the PZT–PCN ceramic systems. 相似文献
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Jingshan Hou Xin Yin Yongzheng Fang Fuqiang Huang Weizhong Jiang 《Journal of luminescence》2012,132(5):1307-1310
A series of single-composition phosphors Ca9MgM′(PO4)7:xEu2+, yMn2+ (CMM′ P:Eu2+, Mn2+; M′=Li, Na, K; 0.003≤x≤0.03; 0 ≤y≤0.1) were synthesized by solid state reactions. Upon excitation at 337 nm, phosphors Ca9MgM′ (PO4)7: Eu2+ exhibit strong blue emissions centered at 417 (Ca9MgLi(PO4)7:Eu2+), 457 (Ca9MgNa(PO4)7:Eu2+), and 453 (Ca9MgK(PO4)7:Eu2+) nm respectively, which correspond to the 4f65d1→4f7 transitions of Eu2+ ions, Through an effective resonance-type energy transfer, CMM′P:Eu2+,Mn2+ phosphors exhibit a series of colors by adjusting the concentration of Mn2+. The result indicates that CMM′P:Eu2+,Mn2+ can be potentially used as a UV excited phosphor for white light-emitting diodes (LEDs). 相似文献
20.
The ‘simple’ perovskites ACr(IV)O3 (A=Sr, Ca, Pb) have been synthesized at high pressure and temperature. Their microstructure and properties are discussed. Specific heat and susceptibility measurements indicate an antiferromagnetic ordering at low temperature in CaCrO3, which is confirmed to be of the C-type by neutron diffraction. 相似文献