共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
In this paper, we present the photoluminescence properties of Pr3+-, Sm3+- and Dy3+-doped germanate glasses and glass ceramics. From the X-ray diffraction measurement, the host glass structure was determined. These glasses have shown strong absorption bands in the near-infrared (NIR) region. Compared to Pr3+-, Sm3+- and Dy3+-doped glasses, their respective glass ceramics have shown stronger emissions due to the Ba2TiGe2O8 crystalline phase. For Pr3+-doped glass and glass ceramic, emission bands centered at 530 nm (3P0→3H5), 614 nm (3P0→3H6), 647 nm (3P0→3F2) and 686 nm (3P0→3F3) have been observed with 485 nm (3H4→3P0) excitation wavelength. Of them, 647 nm (3P0→3F2) has shown bright red emission. Emission bands of 4G5/2→6H5/2 (565 nm), 4G5/2→6H7/2 (602 nm) and 4G5/2→6H9/2 (648 nm) for the Sm3+:glass and glass ceramic, with excitation at 6H5/2→4F7/2 (405 nm) have been recorded. Of them, 4G5/2→6H7/2 (602 nm) has shown a bright orange emission. With regard to the Dy3+:glass and glass ceramic, a bright fluorescent yellow emission at 577 nm (4F9/2→6H13/2) has been observed, apart from 4F9/2→6H11/2 (667 nm) emission transition with an excitation at 454 nm (6H15/2→4I15/2) wavelength. The stimulated emission cross-sections of all the emission bands of Pr3+, Sm3+ and Dy3+:glasses and glass ceramics have been computed based on their measured full-width at half-maxima (FWHM, Δλ) and lifetimes (τm). 相似文献
3.
Eu3+ ion doped chlorophosphate glass ceramics containing nanocrystals were successfully prepared, and their spectroscopic characterizations were done using absorption, excitation and emission spectra. For the crystallized samples, X-ray diffraction (XRD) and transmission electron microscopy (TEM) experiments evidenced the formation of CaCl2 nanocrystals. The absorption and emission spectra investigations indicate that a considerable amount of Eu3+ ions was trapped in CaCl2 nanocrystals, and therefore an efficient up- and down-frequency conversion was observed. The comparative spectroscopic studies of Eu3+ doped samples suggest that the investigated glass ceramics systems are potentially applicable as frequency-conversion photonics devices. 相似文献
4.
A systematic investigation on fluorescence spectroscopy of trivalent thulium doped in oxyfluoride glass ceramics containing LaF3 nanocrystals has been carried out in a spectral range from 400 to 900 nm under the direct excitation of 1D2 level at a low temperature. Specific optical transitions related to the fluorescence emissions are studied based on experimental measurements in frequency and time domain. Fluorescence emissions from the ions in crystal phase are distinguished from what in glass phase and their spectroscopic properties are explored. The dynamical process shows that the temporal decay of fluorescence emission consists of two parts: a rapid decay from the ions in glass phase and a slower decay from the ions in crystal phase. 相似文献
5.
Optical absorption, Electron Paramagnetic Resonance (EPR) studies are carried out on lead zinc phosphate glass systems doped with Cr3+ and VO2+. From optical absorption investigations the crystal-field parameters Dq, B and C are evaluated. EPR measurements on Cr3+ systems indicate that Cr3+ ions are located at sites with low symmetry. EPR spectra of vanadyl doped system revealed the characteristic nature of vanadyl ion. Spin-Hamiltonian and hyperfine values are evaluated for both the systems. Optical absorption spectra of vanadyl doped system revealed three bands that are characteristic of VO(II) ion in tetragonally distorted octahedral site. By correlating both EPR and optical data, the dipolar coupling constant (P) and Fermi-constant coupling parameter (κ) and molecular orbital coefficients β?2, eπ?2 are evaluated. Electron Paramagnetic Resonance and optical absorption studies showed that the chemical bonds of Cr3+ ions and VO2+ ions with the ligands have more covalent nature. From these studies it is also observed that lead spinals are playing major key role in sustaining the covalent nature of bonding. 相似文献
6.
The glasses with composition (50−X)PbO–XSrO-25TiO2-25B2O3 (where X=0, 5, 10 and 15 mol%) were prepared using conventional quenching technique. The Tg, Tc, density and CTE of the glass samples were measured. The Tg observed to increase with increasing concentration of SrO, while the Tc first decreased and then increased. The glass samples were converted to glass ceramics by following two stage heat treatment schedule. The glass ceramic samples were characterized by XRD, SEM and dielectric measurements. The XRD results revealed the formation of ferroelectric lead titanate as a major crystalline phase in glass ceramics. Additional phases observed include Sr2B2O5 and PbB2O4. The room temperature (RT) dielectric constant of glass and glass ceramics are in the range of 100–120 which is promising for capacitor application. 相似文献
7.
Lead-Cadmium fluorosilicate stable glasses were prepared and the vitreous domain region determined in the composition diagram. Characteristic temperatures were obtained from thermal analysis and the structural studies performed illustrate clearly the role played by lead atoms in the glasses crystallization behavior and the glass-forming ability of cadmium atoms. The occurrence of either a cubic lead fluoride or a lead-cadmium fluoride solid solution in crystallizing samples was found to be dependent on Er3+ doping. The optically active ions were found to concentrate in the crystalline phase and in fact play the role of nucleating agent as suggested from X-ray diffraction and EXAFS measurements. 相似文献
8.
Guoping Dong 《Optics Communications》2007,274(2):466-470
Transparent glass ceramics were prepared by heat treating of the as-prepared 80GeS2 · 10Ga2S3 · 10CdI2 glass at 370 °C (Tg + 15 °C) for 72 h (labeled as GGCd10-370). The existence of α-CdGa2S4 crystal in GGCd10-370 glass ceramics has been testified by XRD and Raman spectroscopy. Using the typical Maker fringe technique, SHG was observed in the original transparent GGCd10-370 glass ceramics successfully, which is mainly ascribed to the α-CdGa2S4 nonlinear optical microcrystal. And the SH intensity is almost 0.8 times larger than that of the standard quartz reference. It can be also deduced that the thickness of crystalline layer is a little larger than the coherent length, lc ≈ 2.7 μm. 相似文献
9.
I. V. Silkin Yu. M. Koroteev S. V. Eremeev G. Bihlmayer E. V. Chulkov 《JETP Letters》2011,94(3):217-221
The electronic structure of ternary compounds Pb2Sb2Te5, Pb2Bi2Te5, and Pb2Bi2Se5, which have a layered structure that consists of nine-layer atomic blocks separated by van der Waals gaps, has been theoretically
studied. It has been shown that all studied compounds are three-dimensional topological insulators. The possibility of the
existence of a two-dimensional topological insulator has been found in ultrathin (0001) Pb2Sb2Te5 and Pb2Bi2Te5 films. Oscillations of the ℤ2 topological invariant with an increase in the film thickness have been observed in the latter compound. 相似文献
10.
Neodymium doped bismuth layer structure ferroelectrics (BLSFs) ceramics CaBi4−xNdxTi4O15 (x=0, 0.25, 0.50, 0.75) were prepared by solid-state reaction method. X-ray diffraction pattern showed that single phase was formed when x=0-0.75. The refined lattice parameters showed that a (b) axes decrease at x=0.25 and increase with more Nd3+ dopant. The effects of Nd3+ doping on the dielectric and ferroelectric properties of CaBi4Ti4O15 ceramics are studied. Nd3+ dopant decreased the Curie temperature linearly, and the dielectric loss, tan δ, as well. The remnant polarization of Nd3+ doped CaBi4Ti4O15 ceramics was increased by 80% at x=0.25, while more Nd3+ dopant decreased the remnant polarization. CaBi3.75Nd0.25Ti4O15 ceramics had the largest piezoelectric constant d33. The structure and properties of CaBi4−xNdxTi4O15 ceramics showed that Nd3+ may occupy different crystal locations when Nd3+ content x is less than 0.25 and more than 0.50. 相似文献
11.
12.
Highly efficient transparent Zn2SiO4:Mn2+ film phosphors on quartz substrates were deposited by the thermal diffusion of sputtered ZnO:Mn film. They show a textured structure with some preferred orientations. Our film phosphor shows, for the best photoluminescence (PL) brightness, a green PL brightness of about 20% of a commercial Zn2SiO4:Mn2+ powder phosphor screen. The film shows a high transmittance of more than 10% at the red-color region. The excellence in PL brightness and transmittance can be explained in terms of the textured crystal growth with a continuous gradient of Zn2SiO4: Mn2+ crystals. 相似文献
13.
Pb2, which occurs in lead vapor, was studied by the technique of laser-induced fluorescence using single-mode Ar-laser excitation. The fluorescence observed could be classified into the F-X system. Ten progressions involving vibrational quantum numbers v′ = 0?9 and v″ = 0?22 were analyzed. Including collision-induced lines, rotational quantum numbers from J = 25 to J = 300 were observed. The vibrational constants and the numbering of the states had to be reassigned. For the first time rotational constants were determined for the Pb2 molecule. The internuclear distances of 208Pb2 in the F and X state are and , respectively. Using the constants derived RKR potentials and Franck-Condon factors were calculated, which confirmed the vibrational assignments and constants. 相似文献
14.
Yb:Sc2O3 transparent ceramics are fabricated by a conventional ceramic process and sintering in H2 atmosphere. The room-temperature spectroscopic properties are investigated, and the Raman spectrum shows an obvious vibration characteristic band centred at 415 cm-1. There are three broad absorption bands around 891, 937, and 971 nm, respectively. The strongest emission peak is centred at 1.04 μm with a broad bandwidth (11 nm) and an emission cross-section of 1.8×10^-20 cm^2. The gain coefficient implies a possible laser ability in a range from 990 nm to 1425 nm. The energy-level structure shows that Yb:Sc2O3 ceramics have large Stark splitting at the ground state level due to their strong crystal field. All the results show that Yb:Sc2O3 transparent ceramics are a promising material for short pulse lasers. 相似文献
15.
采用Gaussian 98程序,运用B3LYP方法,对Pd和Pb原子采用收缩价基组LANL2DZ,对Pb2和PdPb2分子的微观结构进行了理论计算. 由于Pb2分子离解后一个Pb原子处于基态,另一个Pb原子处于激发态,采用最小二乘法拟合Pb2分子的势能函数,选用的函数形式为Murrell-Sorbie势能函数加上开关函数. 使用多体展式理论导出了势函数中的参数进而给出PdPb2分子基态势函数的解析表达式,其势能面准确地复现了PdPb2分子的两个稳定构型(C2V和C∞v)及其能量关系.
关键词:
2')" href="#">Pb2
2')" href="#">PdPb2
势能函数 相似文献
16.
A new stable, mobile zigzag-shaped domain wall configuration has been discovered in the Gd2(MoO4)3 and Pb3(PO4)2 structures. Previous work on these materials had not predicted this type of domain wall. The zigzag walls have mobilities 30–40 times that of planar walls in the same material. This increased mobility can be explained as a geometrical effect. 相似文献
17.
Botao Wu Shifeng Zhou Jinjun Ren Yanbo Qiao Danping Chen Congshan Zhu Jianrong Qiu 《Journal of Physics and Chemistry of Solids》2008,69(4):891-894
Transparent Ni2+-doped MgO–Al2O3–SiO2 glass ceramics without and with Ga2O3 were synthetized. The precipitation of spinel nanocrystals, which was identified as solid solutions in the glass ceramics, could be favored by Ga2O3 addition and their sizes were about 7.6 nm in diameter. The luminescent intensity of the Ni2+-doped glass ceramics was largely enhanced by Ga2O3 addition which could mainly be caused by increasing of Ni2+ in the octahedral sites and the reduction of the mean frequency of phonon density of states in the spinel nanocrystals of solid solutions. The full width at half maximum (FWHM) of emissions for the glass ceramics with different Ga2O3 content was all more than 200 nm. The emission lifetime increased with the Ga2O3 content and the longest lifetime is about 250 μs. The Ni2+-doped transparent glass ceramics with Ga2O3 addition have potential application as broadband optical amplifier and laser materials. 相似文献
18.
This paper reports data obtained on the heat capacity of PbSiO3 and Pb2SiO4 within the 390–850-K temperature range. 相似文献
19.
20.
A crystal field investigation of Er3+-doped Sc2O3 transparent ceramics is presented.The established energy level diagram is analyzed with crystal-field Hamiltonian of C2 symmetry including J-mixing effect. Very satisfactory correlations were obtained between 53 calculated and experimental Stark energy levels, with an rms of 7.7 cm−1. These results are compared with those reported for other rare earth ions in the same host and with Er3+ ions in other sesquioxides. The concordance between the crystal-field strength parameters indicates the consistence of our analysis. Furthermore, based on the extended electrostatic point charge model, a theoretical trend is proposed for rare earth ions in Sc2O3 in comparison with Y2O3. Based on this trend, very satisfactory results are obtained for Yb3+ ion in Sc2O3. 相似文献