共查询到20条相似文献,搜索用时 15 毫秒
1.
Multi-color long lasting phosphorescent (LLP) phenomenon in β-Zn3(PO4)2:Mn2+,Zr4+ was systematically investigated. It is found that the red (λEm=616 nm) LLP performance of Mn2+ such as brightness and duration is largely improved, and that the blue (λEm=475 nm) LLP of Zr4+ with lower intensity appears when Zr4+ ions are co-doped into the matrix. The fluorescence, phosphorescence and thermoluminescence (TL) spectra show that Mn2+ ion is solely expected as a luminescent center, while Zr4+ ion not only acts as a luminescent center, but also induces an electron trap (TrapZr) associated with a TL peak at 344 K. The trap depth for TrapZr is 0.25 eV, while that for the intrinsic trap is 0.38 eV, associated with a dominant peak at 385 K for Zn3(PO4)2:Mn2+. The Zr4+-induced trap with suitable depth is responsible for the improvement of the red LLP of Mn2+ ion and the appearance of the blue LLP of Zr4+ ion. The LLP mechanism is also investigated. 相似文献
2.
Zheng Wen-Chen Wu Shao-Yi Zhao Bei-JunZhu Shi-Fu 《Journal of Physics and Chemistry of Solids》2002,63(5):895-897
The substitutional sites of Co2+ ions in Co2+-doped CuG1−xAlxSe2 (including CuGaSe2 where x=0 and CuAlSe2 where x=1) semiconductors are studied by analyzing the composition x dependence of optical spectral parameters reported in the previous literature for these materials. From the studies, we suggest that Co2+ occupy I-group cation site rather than III-group cation site. The suggestion is discussed. 相似文献
3.
M. Kranj?ec I.P. Studenyak V.S. Dyordyay 《Journal of Physics and Chemistry of Solids》2004,65(5):1015-1020
Temperature behaviour of optical absorption edge in Cu6PS5I1−xBrx mixed crystals is studied in the interval 77-325 K. It is shown that the absorption edge has Urbach shape in the 215-325 K temperature interval. The influence of temperature and compositional disorder on the Urbach absorption edge parameters is presented. The mechanism of the Urbach bundle formation and the effect of I→Br anionic substitution on the exciton-phonon interaction parameters is elucidated. 相似文献
4.
N.V. Joshi Jorge Luengo Silvana Alvarez J. Martin 《Journal of Physics and Chemistry of Solids》2005,66(11):2011-2014
[ ]Cd1−x Mnx Ga2S4 is a semimagnetic semiconductor and it has revealed an exceptional property namely ‘optical activity‘. Therefore, a spectroscopic investigation of chiral absorption bands has been carried out with the view to examine the role of d*-d states of manganese atoms. It has been found that inner transitions of Mn++ dominate the spectral region with a special feature, indicating that these transitions show the presence of a substantial contribution from the magnetic dipole moment which rotates the electric vector of the incident polarized radiation. The origin is associated to the lack of a symmetry center caused by the ordered vacancies in this defect compound. 相似文献
5.
A series of SmCoAsO1−xFx (with x=0, 0.05, 0.1, and 0.2) samples have been prepared by solid state reactions. X-ray powder diffraction proved that all samples can be indexed as a tetragonal ZrCuSiAs-type structure. A clear shrinkage of the lattice constants a and c with increasing F content indicated that F has been doped into the lattice. The magnetic and transport properties of the samples have been investigated. Parent SmCoAsO compound exhibited complicated magnetism including antiferromagnetism, ferromagnetism, and ferrimagnetism. For the fluorine doped samples, the antiferromagnetic Néel temperatures were almost independent of the F content and metamagnetic transitions were observed below antiferromagnetic Néel temperatures. With increasing F content, high temperature (below 142 K) ferrimagnetic state gradually changed to ferromagnetic state. In the resistivity result, metallic conduction in the region of 2-300 K and Fermi liquid behavior at low temperatures were shown in all samples. Transport properties at applied magnetic fields showed anomalies at low temperatures. 相似文献
6.
E.V. Zenkov 《Journal of Physics and Chemistry of Solids》2010,71(9):1295-1300
Ternary PdMnxFe1−x alloys are known to form a microinhomogeneous random mixture of PdMn and PdFe phases. The unconventional ρ(x) dependence of dc resistivity and singularities in low frequency optical conductivity spectra of alloys are described footing within the effective medium approach. The essential point of the model proposed is the anomalous role of insulating interfaces, whose proliferation at intermediate x gives rise to the observed maximum of resistivity near x?0.8. 相似文献
7.
Jing Ju Jun Tang Masanori Watahiki Hidenori Terasaki Hirotsugu Takizawa 《Journal of Physics and Chemistry of Solids》2010,71(4):491-494
Synthetic conditions such as stoichiometries, temperature and pressure are optimized to achieve a high quality oxygen deficient SmFeAsO0.6 superconductor. Both electric and magnetic measurements show a sharp superconducting transition at about 55 K. Several important physical parameters are deduced. The apparent superconducting gap observed in heat capacity with 2Δo/kBTc of 4.57 larger than that of previous fluorine replaced samples indicate that this superconductivity will not strongly conflict with the phonon-mediated BCS mechanism. The mean free length ?=18.8 nm and the coherent length ξ=2.3-3.3 nm show that the superconductivity is in the clean limit. 相似文献
8.
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
9.
T.K. Seshagiri T.K. Gundu Rao V. Natarajan S.V. Godbole 《Journal of Physics and Chemistry of Solids》2009,70(9):1261-1266
Yttrium borate doped with uranium was prepared by mixing and heating yttrium oxide obtained through oxalate precipitation route, boric acid and requisite amount of nuclear-grade uranium oxide at high temperature. Photoluminescence (PL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) studies were carried out on gamma-irradiated doped/undoped yttrium borate samples in the temperature range 300-600 K. TSL studies showed the presence of two glow peaks at 414 and 471 K. PL studies along with lifetime decay investigation suggested uranium goes in the matrix as UO22+. EPR studies showed the presence of O2−radical ion along with electron trapped in defect centres, which might have been produced for charge compensation. Apart from this, CO2− radical was also observed in the system having its origin from residual oxalate ion. Temperature dependence EPR studies of the observed radical confirmed the involvement of the CO2− and dioxide radical ion in the observed glow peaks. By correlating the TSL, PL and ESR data, probable mechanism is proposed for the observed TSL glow in the system. 相似文献
10.
A method is described which is capable of simulating disorder across a range of composition. It is used to study the disorder of iron and aluminium on the octahedral and tetrahedral cation sites in the Brownmillerite phase Ca2FexAl2−xO5. The arrangements with the lowest lattice energies are those that maximize the number of Fe3+ on octahedral sites throughout the composition range. An exchange of one Fe3+ with one Al3+, which results in a decrease in the number of iron ions on octahedral sites, increases the lattice energy by an amount that is dependent on x but is independent of the number of exchanges. The exchange of trivalent cations also results in an expansion in the b lattice direction, accompanied by a decrease in the a and c directions across the full range of composition. 相似文献
11.
We report on the enhanced electromechanical, magnetic and magnetoelectric properties of Bi1−xCaxFe1−xTixO3 solid solutions. The crystal structure of the x≈0.25 compounds are close to the rhombohedral-orthorhombic phase boundary, and the solid solutions are characterized by increased electromechanical properties due to the polarization extension near the polar-nonpolar border. The homogenous weakly ferromagnetic state is established at x>0.15 doping. The chemical doping shifts the magnetic transition close to room temperature, thus enlarging the magnetic susceptibility of the compounds. The solid solutions at the morphotropic phase boundary exhibit a nearly twofold increase in piezoelectric response, whereas the magnetoelectric coupling shows five times enhancement in comparison with the parent bismuth ferrite. 相似文献
12.
F.C. Ragel P. de V. du Plessis A.M. Strydom 《Journal of Physics and Chemistry of Solids》2010,71(12):1694-1701
The solid solution (Ce1−xLax)PtGa has been studied through X-ray diffraction, magnetization (σ(B)), magnetic susceptibility (χ(T)), electrical resistivity (ρ(T)), magnetoresistivity (MR) and heat capacity (CP(T)) measurements. The Néel temperature (TN=3.3 K) for CePtGa is lowered upon La substitution as observed from χ(T) and ρ(T) measurements. The Kondo temperature TK as calculated from MR measurements is comparable to TN and also decreases with La substitution. The volume dependence of TK is in accordance with the compressible Kondo lattice model and a Doniach diagram of the results is presented. CP(T) measurements are presented for CePtGa, Ce0.2La0.8PtGa and LaPtGa and the results are discussed in terms of the electronic and magnetic properties. Other features of interest are anomalies in ρ(T) and CP(T) due to crystalline electric field effects and metamagnetism as observed in σ(B) studies for samples with 0≤x≤ 0.3. 相似文献
13.
Phonon dynamics was investigated on Y Mn1−xFexO3(0≤x≤0.20) hexagonal manganite polycrystals. Phonon modes were properly assigned using results obtained on Y MnO3 single crystal, by mixing the ab plane and the c axis optical responses. Upon increasing the Fe content, most of the phonon mode frequencies do not vary drastically. However, some modes involving Y and O atom displacements along the c axis are affected by doping. Indeed, a redshift of their transverse optical frequency was interpreted as an elongation of Y-O distance along the c-axis, resulting in a change in yttrium coordination. 相似文献
14.
Ran Pang Chengyu Li Lili Shi Qiang Su 《Journal of Physics and Chemistry of Solids》2009,70(2):303-306
By introducing the Y3+ into Sr2P2O7:Eu2+, we successfully prepared a kind of new phosphor with blue long-lasting phosphorescence by the high-temperature solid-state reaction method. In this paper, the properties of Sr2P2O7:Eu2+,Y3+ were investigated utilizing XRD, photoluminescence, luminescence decay, long-lasting phosphorescence and thermoluminescence (TL) spectra. The phosphor emitted blue light that was related to the 4f65d1-8S7/2 transition of Eu2+. The bright blue phosphorescence could be observed by naked eyes even 8 h after the excitation source was removed. Two TL peaks at 317 and 378 K related to two types of defects appeared in the TL spectrum. By analyzing the TL curve the depths of traps were calculated to be 0.61 and 0.66 eV. Also, the mechanism of LLP was discussed in this report. 相似文献
15.
E.A MahmoudM.M El-Samanoudy A.S Abd Rabo 《Journal of Physics and Chemistry of Solids》2002,63(11):2003-2010
Optical absorption at room temperature and electrical conductivity at temperatures between 283 and 333 K of vacuum evaporated GexFexSe100−2x (0≤x≤15) amorphous thin films have been studied as a function of composition and film thickness. It was found that the optical absorption is due to indirect transition and the energy gap increases with increasing both Ge and Fe content; on the other hand, the width of the band tail exhibits the opposite behavior. The optical band gap Eopt was found to be almost thickness independent. The electrical conductivity show two types of conduction, at higher temperature the conduction is due to extended states, while the conduction at low temperature is due to variable range hopping in the localized states near Fermi level. Increasing Ge and Fe contents were found to decrease the localized state density N(EF), electrical conductivity and increase the activation energy for conduction, which is nearly thickness independent. Variation of the atomic densities ρ, molar volume V, glass transition temperature Tg cohesive energy C.E and number of constraints NCo with average coordination number Z was investigated. The relationship between the optical gap and chemical composition is discussed in terms of the cohesive energy C.E, average heat of atomization and coordination numbers. 相似文献
16.
P. Przybylski A.P. PikulD. Kaczorowski P. Wiśniewski 《Journal of Physics and Chemistry of Solids》2014
Physical properties of polycrystalline samples of CeCuxGa4−x (x = 0.2–1.4), crystallizing in the tetragonal BaAl4-type structure (space group I 4/mmm), were studied by means of X-ray powder diffraction, magnetization, specific heat, electrical resistivity and magnetoresistivity measurements in wide temperature and magnetic fields ranges. The unit-cell volume of the system was found to decrease with increasing x (in total by about 4%) but the magnetic moments of Ce3+ ions remain localized in the whole x-range studied. The alloys exhibit ferromagnetic order at low temperatures, which manifests itself as distinct and relatively sharp anomalies in all the temperature characteristics measured. The ordering temperature decreases with increasing the Cu content from 5.5(1) K for x = 0.2 down to 1.35(5) K for x = 1.4, and the electrical transport properties of the system show some features characteristic of Kondo lattices. 相似文献
17.
Junjun Zhang Linlin Li Wenwen Zi Na Guo Lianchun Zou Shucai Gan Guijuan Ji 《Journal of Physics and Chemistry of Solids》2014
Tetragonal CaMoO4 and CaMoO4:Eu3+ with various novel three-dimensional (3D) hierarchical architectures were successfully synthesized via a facile, efficient sonochemistry process in the absence of any surfactant or template. XRD, EDS, FE-SEM, and photoluminescence (PL) were employed to characterize the as-obtained products. It was found that morphology modulation could be easily realized by changing pH value of the precursor. The pH value of the precursor not only affected the substructures of the hierarchical structures, but also determined the size distributions of the final products. The formation mechanism for different hierarchical architectures was proposed on the basis of time-dependent experiments. The luminescence spectra showed that CaMoO4:Eu3+ phosphors can be effectively excited by the near ultraviolet (UV) (396 nm) and blue (466 nm) light, and exhibited strong red emission around 615 nm, which was attributed to the Eu3+5D0→7F2 transition. Compared with Y2O3:Eu3+ phosphor, CaMoO4:Eu3+ is much more stable, efficient and suitable, therefore, this phosphors could be a promising red component for possible applications in the field of LEDs. 相似文献
18.
Sung-Ho Han Falah S. Hasoon Allen M. Hermann 《Journal of Physics and Chemistry of Solids》2005,66(11):1895-1898
Spectroscopic ellipsometry measurements of CuInSe2 (CIS) and CuIn1−xGaxSe2 (CIGS) over a range of Cu compositions reveal that there are important differences in electronic and optical properties between α-phase CIS/CIGS and Cu-poor CIS/CIGS. We find a reduction in the imaginary part of the dielectric function ?2 in the spectral region, 1-3 eV. This reduction can be explained in terms of the Cu-3d density of states. An increase in band gap is found for Cu-poor CIS and CIGS due to the reduction in repulsive interaction between Cu-3d and Se-4p states. We also characterize the dielectric functions of polycrystalline thin-film α-phase CuIn1−xGaxSe2 (x=0.18 and 0.36) to determine their optical properties and compare them with similar compositions of bulk polycrystalline CuIn1−xGaxSe2. The experimental results have important implications for understanding the functioning of polycrystalline optoelectronic devices. 相似文献
19.
Xue Yu 《Journal of Physics and Chemistry of Solids》2009,70(8):1146-1149
Nanoscaled Zn2SiO4:Mn2+ green phosphor with regular and uniform morphology was synthesized by hydrothermal method at a low temperature of 140 °C. The structure and morphology of the phosphor was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of the hydrothermal temperature and the time on the crystallite structure and the vacuum ultraviolet (VUV) photoluminescence (PL) properties were evaluated. The as-synthesized nanoscaled Zn2SiO4:Mn2+ phosphor exhibited intensive broad emission around 523 nm, which was attributed to the 4T1→6A1 transition of Mn2+. The PL intensity increased along with the increasing hydrothermal temperature and time. The heat-treated phosphors exhibited higher PL intensity than the corresponding samples prepared using the conventional solid-state reaction. 相似文献
20.
Yoshiyuki Yoshida Kotaro Iwata Naofumi Aso 《Journal of Physics and Chemistry of Solids》2011,72(5):559-561
We have measured magnetization curves and powder neutron diffraction of double-layered Ruddlesden-Popper type ruthenate Sr3−xCaxRu2O7 (x=1.5, 2.0 and 3.0). The field dependence of the magnetization revealed that the transition field of metamagnetic transition along the b-axis shifted to lower fields and that the transition became broad with increasing Sr content. The slope of the magnetization curve also increased with increasing Sr content below the metamagnetic transition. These results indicate that an itinerant component is partly introduced by the Sr substitution. From the magnetic reflection, on cooling below TN, an additional reflection was observed at (0 0 1) for each x, and the amplitude increased with decreasing temperature. The observed diffraction patterns are very similar to those of Ca3Ru2O7. We conclude that the magnetic structure of the antiferromagnetic ordered phase is basically the same structure with that of Ca3Ru2O7. 相似文献