共查询到20条相似文献,搜索用时 15 毫秒
1.
Akira Doi 《Journal of Physics and Chemistry of Solids》2005,66(6):1091-1100
Comparison was made between crystals of thallium chloride and silver chloride on their biasing effects with dc/ac voltage. Previous reports say that, although their electrical conductivities are similar, the dominant charge carriers in the former are the Cl− ions while the Ag+ ions in the latter. The present dc/ac study demonstrates the following: for thallium chloride, although Cl− conduction may be dominant under low bias field, Tl+ conduction supercedes Cl− conduction when the bias field is enhanced. For silver chloride, Ag+ conduction is overwhelming within wide temperature range, to cause easy dielectric breakdown on dc biasing. Concerning the extrinsic conductivity seen at temperatures below 60 °C (thallium chloride) or below 150 °C (silver chloride), it is ascribed to grain-boundary related electron conduction, not to grain-boundary related Tl+ or Ag+ conduction as reported earlier. 相似文献
2.
A.N. Papathanassiou 《Journal of Physics and Chemistry of Solids》2005,66(10):1849-1850
A power law used to describe the AC conductivity from 299 to 393 K of the mixed crystal (NH4)3H(SO4)1.42(SeO4)0.58 led to fractional exponent values ranging from 1.08 to 0.91, depending on structural changes induced on temperature variation [B. Louati, M. Gargouri, K. Guidara and T. Mhiri, J. Phys. Chem. Solids 66 (2005) 762]. In the present note, we suggest that the fractional law exhibits features of lattice relaxation. Despite the structural changes, the parameters of the power law are mutually interconnected to yield a temperature independent phenomenon. Such behavior is probably of general validity and characterizes the universal fractional dispersion of the AC conductivity, as it was also observed in glasses of different composition. 相似文献
3.
H.O. Rodrigues G.F.M. Pires Junior J.S. Almeida A.C. Ferreira M.A.S. Silva 《Journal of Physics and Chemistry of Solids》2010,71(9):1329-2539
In this paper we studied the effects of Bi2O3 and PbO addition on BiFeO3 (BFO) ceramic matrix. The structural, dielectric and magnetic properties of fifteen BFO samples were discussed in view of possible applications in RF and microwave devices. The present work also reports the preparation of the samples. Polyvinyl alcohol (PVA) and tetraethyl orthosilicate (TEOS) were also added as a binder in the fabrication procedure. The samples have been studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and magnetic hysteresis measurements. Further, a study based on impedance spectroscopy also has been done. Dielectric permittivity (ε′) and dielectric loss (tan δ) were measured at room temperature in the frequency range 100 Hz-10 MHz, as well as a.c. conductivity. The -Im[Z(f)] versus Re[Z(f)] plot has been obtained. The samples were investigated in view of possible applications like miniaturized filters, diplexers and dielectric resonator antennas (DRA). In the RF and MW frequency region, the application of magneto-dielectric and multiferroic perovskite composite materials is desirable for the miniaturization of components. 相似文献
4.
Pooja Varshney Sarita Afaq Ahmad Saba Beg 《Journal of Physics and Chemistry of Solids》2006,67(11):2305-2309
Electrical conductivity of ZrO2 doped with Pb3O4 has been measured at different temperatures for different molar ratios (x=0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06). The conductivity increases due to migration of vacancies, created by doping. The conductivity increases with increase in temperature till 180 °C and thereby decreases due to collapse of the fluorite framework. A second rise in conductivity at higher temperatures beyond 500-618 °C is due to phase transition of ZrO2. DTA and X-ray powder diffraction were carried out for confirming doping effect and transition in ZrO2.The addition of Pb3O4 to ZrO2 shifted the phase transition of ZrO2 due to the interaction between Pb3O4 and ZrO2. 相似文献
5.
It was discovered that the well-known higher boride YB66, one of the first reported phonon glass electron crystals (PGEC), could be obtained in a much more metal-rich composition than previously thought possible. Using the floating zone growth method, YB48 single crystals with YB66 crystal structure could be obtained, and their thermoelectric properties measured. This expansion of the homogeneity range of the well-known YB66 compound is surprising and a new Y atomic site was discovered. YB48 exhibits much higher power factors than YB66 which increase rapidly with increasing temperature. The obtained dimensionless figure of merit of this compound at 990 K is approximately 30 times higher than that of previously reported YB66 samples, and higher than any other pristine higher boride. This discovery reveals YB48 as a promising high temperature thermoelectric material. 相似文献
6.
M. Potoczek 《Journal of Physics and Chemistry of Solids》2006,67(12):2528-2535
Electrical conductivity of molybdenum disulphide was studied in a helium-sulphur gas mixture as a function of temperature (1073-1273 K). It was found that over the whole temperature and sulphur pressure range (10-6600 Pa) studied, the material exhibits p-type conductivity. Based on literature intrinsic electronic disorder data as well as measured electrical conductivity results a defect model has been proposed. This model involves electron holes and doubly ionized interstitial sulphur ions as majority point defects as well as electrons and acceptor-type foreign ions as minority defects. 相似文献
7.
The Ce6−xYxMoO15−δ solid solution with fluorite-related structure have been characterized by differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffraction (XRD), IR, Raman, scanning electric microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) methods. The electric conductivity of samples is investigated by Ac impedance spectroscopy. An essentially pure oxide-ion conductivity of the oxygen-deficiency was observed in pure argon, oxygen and air. The highest oxygen-ion conductivity was found in Ce5.5Y0.5MoO15−δ ranging from 5.9×10−5 (S cm−1) at 300 °C to 1.3×10−2 (S cm−1) at 650 °C, respectively. The oxide-ion conductivities remained stable over 80 h-long test at 800 °C. These properties suggested that significant oxide-ionic conductivity exists in these materials at moderately elevated temperatures. 相似文献
8.
Electrical impedance measurements of Na3H(SO4)2 were performed as a function of both temperature and frequency. The electrical conductivity and dielectric relaxation have been evaluated. The temperature dependence of electrical conductivity reveals that the sample crystals transformed to the fast ionic state in the high temperature phase. The dynamical disordering of hydrogen and sodium atoms and the orientation of SO4 tetrahedra results in fast ionic conductivity. In addition to the proton conduction, the possibility of a Na+ contribution to the conductivity in the high temperature phase is proposed. The frequency dependence of AC conductivity is proportional to ωs. The value of the exponent, s, lies between 0.85 and 0.46 in the room temperature phase, whereas it remains almost constant, 0.6, in the high-temperature phase. The dielectric dispersion is examined using the modulus formalism. An Arrhenius-type behavior is observed when the crystal undergoes the structural phase transition. 相似文献
9.
Zhifeng Wang Nansheng Xu Weizhong Ding Fushen Li 《Journal of Physics and Chemistry of Solids》2011,72(1):50-55
Perovskite compounds in the system of SrCo1−xFexO3−δ (x=0.2, 0.4 and 0.6) were synthesized by solid state reaction. SrCo1−xFexO3−δ shows the p-type small polaron conduction behavior. Electrical conductivity and oxygen vacancy content decrease with increase in Fe content. The incorporation of Fe increases the structural stability of SrCo1−xFexO3−δ at low temperatures, while decreasing the structural stability at high temperatures. Oxygen partial pressure has a strong influence on electrical conductivity. At low oxygen partial pressure, SrCo0.8Fe0.2O3−δ will transform from cubic to orthorhombic structure. This structure can remain in 5%H2/Ar only for a short time and then dissociates into Sr3Fe2O6.64 and Co due to the reduction of B-site elements. 相似文献
10.
W.S. Shih L.W. Ji W. Water K.T. Lam W.C. Chu 《Journal of Physics and Chemistry of Solids》2010,71(12):1760-1762
This study demonstrates that nanocrystalline TiO2 thin films were deposited on ITO/glass substrate by radio-frequency magnetron sputtering. Field-emission scanning electron microscope (FE-SEM) and atomic force microscopic (AFM) images showed the morphology of TiO2 channel layer with grain size and root-mean-square (RMS) roughness of 15 and 5.39 nm, respectively. TiO2 thin-film transistors (TFTs) with sputter-SiO2 gate dielectric layer were also fabricated. It was found that the devices exhibited enhancement mode characteristics with the threshold voltage of 7.5 V. With 8-μm gate length, it was also found that the Ion/off ratio and off-state current were around 1.45×102 and 10 nA, respectively. 相似文献
11.
Shota Miura Hikaru Sasaki Ken-ichi Takagi Takuya Fujima 《Journal of Physics and Chemistry of Solids》2014
Thermoelectric properties of AlMgB14-based materials prepared by spark plasma sintering were investigated. Al, Mg, and B powders were used as raw material powders. The raw powders were mixed using a V-shaped mixer, and then the mixture was sintered at 1673 K or 1773 K. The mixture ratio of raw powders was varied around stoichiometric ratio of AlMgB14. X-ray diffraction patterns of samples showed that all samples consist of AlMgB14 and MgAl2O4. The Seebeck coefficient of the samples exhibited significant change depending on the varying mixture ratio and sintering temperature. One sample exhibited a large negative value for the Seebeck coefficient (approximately −500 μV/K) in the temperature range from 573 K to 1073 K, while others showed positive value (250–450 μV/K). Thus n-type AlMgB14-based material has been realized by varying raw material ratio and sintering temperature. 相似文献
12.
Hiroyuki Kitagawa Machiko Wakatsuki Hiroyuki Noguchi Kazuhiro Hasezaki 《Journal of Physics and Chemistry of Solids》2005,66(10):1635-1639
Temperature dependences of the Hall coefficient, Hall mobility and thermoelectric properties of Ni-doped CoSb3 have been characterized over the temperature range from 20 to 773 K. Ni-doped CoSb3 is an n-type semiconductor and the conduction type changes from n-type to p-type at around 450 K. The temperature for the transition from n-type to p-type increased with increasing Ni content x. The Seebeck coefficient reaches a maximum value near the transition temperature. The electrical resistivity indicates that Co1−xNixSb3 is a typical semiconductor when x≤0.03 and a degenerate semiconductor when x>0.03. Thermal conductivity analyses show that the lattice component is predominant at lower temperatures and carrier and bipolar components become large at temperatures higher than the transition temperature. The thermoelectric figure of merit reaches a maximum value close to the transition temperature and the largest value, 4.67×10−4 K−1 at 600 K, was obtained for x=0.05. 相似文献
13.
Yutaka Nagai Nakahara Kouji Yoneyama Yoshifumi Kawano Katsuyasu Tanaka Katsumi Nakata Ryouhei 《Journal of Physics and Chemistry of Solids》2004,65(11):1861-1870
The characteristics of high-temperature ionic thermocurrent (HT ITC) in CaF2 doped with different sodium concentrations were studied by the Teflon-insulated electrode ITC method. It was shown that, with increasing sodium concentration, the HT ITC band moved toward a Na+-FV dipole band with a peak at 162 K. The results of analyses of the HT ITC spectra using an equivalent electric circuit proved that the activation energy of space charge migration related to HT ITC was also strongly dependent on the doped sodium concentrations if varied from 0.94 to 0.46 eV with increasing sodium concentration in our ITC study. In addition, the broadening of the Na+-FV dipole band was observed in 3 nominal mole% NaF-doped CaF2, which was accompanied by a considerable decrease of the activation energy from 0.46 to 0.29 eV without showing marked temperature shifts of the peak ITC bands. 相似文献
14.
Hui Zhang Mei-Bo Tang Zhen-Yong Man Hao-Hong Chen Xin-Xin Yang 《Journal of Physics and Chemistry of Solids》2009,70(2):312-1257
Structural, magnetic, heat capacity, electrical and thermal transport properties are reported on polycrystalline Ba8Ni6Ge40. Ba8Ni6Ge40 crystallizes in a cubic type I clathrate structure with unit cell a=10.5179 (4) Å. It is diamagnetic with susceptibility χdia=−1.71×10-6 emu/g Oe. An Einstein temperature 75 K and a Debye temperature 307 K are estimated from heat capacity data. It exhibits n-type conducting behavior below 300 K. It shows high Seebeck coefficients (−111×10-6 V/K), low thermal conductivity (2.25 W/K m), and low electrical resistivity (8.8 mΩ cm) at 300 K. 相似文献
15.
16.
M.E. Aydin 《Journal of Physics and Chemistry of Solids》2007,68(9):1770-1773
Electrical transport properties of Ag metal-fluorescein sodium salt (FSS) organic layer-silicon junction have been investigated. The current-voltage (I-V) characteristics of the diode show rectifying behavior consistent with a potential barrier formed at the interface. The diode indicates a non-ideal I-V behavior with an ideality factor higher than unity. The ideality factor of the Ag/FSS/p-Si diode decreases with increasing temperature and the barrier height increases with increasing temperature. The barrier height (φb=0.98 eV) obtained from the capacitance-voltage (C-V) curve is higher than barrier height (φb=0.72 eV) derived from the I-V measurements. The barrier height of the Ag/FSS/p-Si Schottky diode at the room temperature is significantly larger than that of the Ag/p-Si Schottky diode. It is evaluated that the FSS organic layer controls electrical charge transport properties of Ag/p-Si diode by excluding effects of the SiO2 residual oxides on the hybrid diode. 相似文献
17.
Hai-Qin Huang Feng-Juan Liu Jian Sun Jian-Wei Zhao Zuo-Fu Hu Zhen-Jun Li Xi-Qing Zhang 《Journal of Physics and Chemistry of Solids》2011,72(12):1393-1396
We report on the electrical properties of bottom-gate ZnO thin film transistors (TFTs) with different active layer thicknesses. The ZnO active layer films with thickness varied from 20 to 100 nm were deposited by radio frequency (rf) magnetron sputtering on SiO2/p-Si substrate and annealed at a high temperature of 950 °C. The transistor with 40 nm thick ZnO exhibited the best performance, with a field effect mobility of 27.5 cm2/V s, a threshold voltage of −2.4 V and an on/off ratio of 7×103. 相似文献
18.
A.N Papathanassiou J GrammatikakisS Sakkopoulos E VitoratosE Dalas 《Journal of Physics and Chemistry of Solids》2002,63(9):1771-1778
The charge trapping centers in fresh and thermally aged conductive polyaniline-polypyrrole copolymers (starting from pure polyaniline and ending in pure polypyrrole by steps of 10 wt%) were studied by thermally stimulated depolarization current (TSDC) spectroscopy and dc conductivity measurements. One low temperature (115-135 K) relaxation mechanism appears in polyaniline-rich copolymers and disappears after thermal anneal. It is attributed to polaron trapping in the vicinity of chlorine anion dopants. Another relaxation mechanism operates close to room temperature and is related to conformational relaxation, which corresponds to the influence of the annihilation of the conformons on the conduction mechanism. The relaxation is sensitive to thermal aging as a result of the thermal annealing on the conductivity. The temperature derivative of the dc conductivity supports the latter assertion. The activation energy values were obtained as a function of composition for both fresh and heated samples. The TSDC spectroscopy is a sensitive tool which is an alternative to the standard conductivity studies for the characterization of polypyrrole-polyaniline conductive copolymers and the study of the thermal degradation. 相似文献
19.
Ryo EndohNobuhiro Matsumoto Junji AwakaShuji Ebisu Shoichi Nagata 《Journal of Physics and Chemistry of Solids》2002,63(4):669-674
A normal thiospinel CuIr2S4 exhibits a temperature-induced metal-insulator (M-I) transition around 230 K with structural transformation, showing hysteresis on heating and cooling. On the other hand, CuCr2S4 has the same normal spinel structure without the structural transformation. CuCr2S4 has been found to be metallic and ferromagnetic with the Curie temperature Tc~377 K. In order to see the effect of substituting Cr for Ir on the M-I transition, we have carried out a systematic experimental study of electrical and magnetic properties of Cu(Ir1−xCrx)2S4. The M-I transition temperature shifts to lower temperature with increasing Cr-concentration x and this transition is not detected above x~0.05. The ferromagnetic transition temperature decreases as x is decreased and the transition does not occur below x~0.20. 相似文献
20.
Electrical and thermal properties of binary systems consisted of stearine and expanded graphite (EG) of different bulk densities (0.003 and 0.4 g/cm3), stearine and fine-crystalline graphite (CG) were examined. Heat capacity measurements display that phonon spectrum of graphite does not change after chemical and heat treatment in the temperature range from 300 to 700 K. It was shown that the value of samples’ percolation threshold depends on aspect ratio of using the electroconducting filler: EG as electroconducting filler is 20 times more effective than common crystal graphite. 相似文献