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1.
Glasses with the compositions of xLi2O-(70 − x)Nb2O5-30P2O5, x = 30-60, and their glass-ceramics are synthesized using a conventional melt-quenching method and heat treatments in an electric furnace, and Li+ ion conductivities of glasses and glass-ceramics are examined to clarify whether the glasses and glass-ceramics prepared have a potential as Li+ conductive electrolytes or not. The electrical conductivity (σ) of the glasses increases monotonously with increasing Li2O content, and the glass of 60Li2O-10Nb2O5-30P2O5 shows the value of σ = 2.35 × 10−6 S/cm at room temperature and the activation energy (Ea) of 0.48 eV for Li+ ion mobility in the temperature range of 25-200 °C. It is found that two kinds of the crystalline phases of Li3PO4 and NbPO5 are formed in the crystallization of the glasses and the crystallization results in the decrease in Li+ ion conductivity in all samples, indicating that any high Li+ ion conducting crystalline phases have not been formed in the present glasses. 60Li2O-10Nb2O5-30P2O5 glass shows a bulk nanocrystallization (Li3PO4 nanocrystals with a diameter of ∼70 nm) and the glass-ceramic obtained by a heat treatment at 544 °C for 3 h in air exhibits the values of σ = 1.23 × 10−7 S/cm at room temperature and Ea = 0.49 eV.  相似文献   

2.
Chemical preparation, crystal structure, calorimetric, and spectroscopic investigations are given for a new organic-cation dihydrogenomonophosphate, (4-C2H5C6H4NH3)H2PO4 in the solid state. This compound crystallizes in the orthorhombic space group Pbca with the following unit cell parameters: a=8.286(3) Å, b=9.660(2) Å, c=24.876(4) Å, Z=8, V=1991.2(7) Å3, and DX=1.442 g cm−3. Crystal structure was solved with a final R=0.054 for 3305 independent reflections. The atomic arrangement coaled described as H2PO4 layers between which are located the 4-ethylanilinium cations.  相似文献   

3.
The luminescent properties of Ca2Gd8(1−x)(SiO4)6O2:xDy3+ (1% ≤ x ≤ 5%) powder crystals with oxyapatite structure were investigated under vacuum ultraviolet excitation. In the excitation spectrum, the peaks at 166 nm and 191 nm of the vacuum ultraviolet region can be assigned to the O2− → Gd3+, and O2− → Dy3+ charge transfer band respectively, which is consistent with the theoretical calculated value using Jφrgensen's empirical formula. While the peaks at 183 nm and 289 nm are attributed to the f-d spin-allowed transitions and the f-d spin-forbidden transitions of Dy3+ in the host lattice with Dorenbos's expression. According to the emission spectra, all the samples exhibited excellent white emission under 172 nm excitation and the best calculated chromaticity coordinate was 0.335, 0.338, which indicates that the Ca2Gd8(SiO4)6O2:Dy3+ phosphor could be considered as a potential candidate for Hg-free lamps application.  相似文献   

4.
In this paper, a series of pure Ni1 − xZnxFe2O4 (0 ≤ x ≤ 1) spinel ferrites have been synthesized successfully using a novel route through calcination of tailored hydrotalcite-like layered double hydroxide molecular precursors of the type [(Ni + Zn)1 − x − yFey2+Fex3+(OH)2]x+(SO42−)x/2·mH2O at 900 °C for 2 h, in which the molar ratio of (Ni2+ + Zn2+)/(Fe2+ + Fe3+) was adjusted to the same value as that in single spinel ferrite itself. The physico-chemical characteristics of the LDHs and their resulting calcined products were investigated by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Mössbauer spectroscopy. The results indicate that calcination of the as-synthesized LDH precursor affords a pure single Ni1 − xZnxFe2O4 (0 ≤ x ≤ 1) spinel ferrite phase. Moreover, formation of pure ferrites starting from LDHs precursors requires a much lower temperature and shorter time, leading to a lower chance of side-reactions occurring, because all metal cations on the brucite-like layers of LDHs can be uniformly distributed at an atomic level.  相似文献   

5.
The (C3H12N2)0.94[Mn1.50Fe1.50III(AsO4)F6] and (C3H12N2)0.75[Co1.50Fe1.50III(AsO4)F6] compounds 1 and 2 have been synthesized using mild hydrothermal conditions. These phases are isostructural with (C3H12N2)0.75[Fe1.5IIFe1.5III(AsO4)F6]. The compounds crystallize in the orthorhombic Imam space group. The unit cell parameters calculated by using the patterns matching routine of the FULPROOF program, starting from the cell parameters of the iron(II),(III) phase, are: a = 7.727(1) Å, b = 11.047(1) Å, c = 13.412(1) Å for 1 and a = 7.560(1) Å, b = 11.012(1) Å, c = 13.206(1) Å for 2, being Z = 8 in both compounds. The crystal structure consists of a three-dimensional framework constructed from edge-sharing [MII(1)2O2F8] (M = Mn, Co) dimeric octahedra linked to [FeIII(2)O2F4] octahedra through the F(1) anions and to the [AsO4] tetrahedra by the O(1) vertex. This network gives rise two kinds of chains, which are extended in perpendicular directions. Chain 1 is extended along the a-axis and chain 2 runs along the c-axis. These chains are linked by the F(1) and O(1) atoms and establish cavities delimited by eight or six polyhedra along the [1 0 0] and [0 0 1] directions, respectively. The propanediammonium cations are located inside these cavities. The thermal study indicates that the structures collapse with the calcination of the organic dication at 255 and 285 °C for 1 and 2, respectively. The Mössbauer spectra in the paramagnetic state indicate the existence of two crystallographically independent positions for the iron(III) cations and a small proportion of this cation in the positions of the divalent Mn(II) and Co(II) ones. The IR spectrum shows the protonated bands of the H2N- groups of the propanediamine molecule and the characteristic bands of the [AsO4]3− arsenate oxoanions. In the diffuse reflectance spectra, it can be observed the bands characteristic of trivalent iron(III) cation and divalent Mn(II) and Co(II) ones in a distorted octahedral symmetry. The calculated Dq and B-Racah parameters for the cobalt(II) phase are 710 and 925 cm−1, respectively. The ESR spectra of compound 1 maintain isotropic with variation in temperature, being g = 1.99. Magnetic measurements for both compounds indicate that the main magnetic interactions are antiferromagnetic in nature. However, at low temperatures small ferromagnetic components are detected, which are probably due to a spin decompensation of the two different metallic cations. The hysteresis loops give values of the remnant magnetization and coercive field of 84.5, 255 emu/mol and 0.01, 0.225 T for phases 1 and 2, respectively.  相似文献   

6.
New red Ca10K(PO4)7:Eu3+, K+ phosphors were synthesized by solid state reaction and their photoluminescence properties as well as those by co-doping Mo6+ under near ultraviolet excitation were investigated. From the excitation spectra monitored at 611 nm, it can be seen that the strongest excitation peak is situated at 393 nm, well matching with the emission wavelength of near-ultraviolet chips for white LEDs. Upon 393 nm excitation, the brightness of Ca9K(PO4)7:0.5Eu3+, 0.5 K+ with the optimal Eu3+-doping concentration is about 2.3 times stronger than that of the commercial red Y2O3:Eu3+ phosphor. The introducing of Mo6+, which results in a possible variety for the excited energy level of the host, can enhance the brightness of Eu3+ to be maximized by about 15%. The CIE chromaticity coordinates of Ca9K(PO4)7:0.5Eu3+, 0.5 K+ are calculated to (0.654, 0.345), which are close to the (0.67, 0.33) standard of the National Television System Committee. All the above results indicate Eu3+-activated Ca10K(PO4)7 is a potential candidate for white LEDs.  相似文献   

7.
The title compound, (N4C6H21)·(Co(H2PO4)(HPO4)2), was prepared hydrothermally (473 K, 10 days, autogenous pressure), in the presence of the tris(2-aminoethyl)amine as organic template. Its structure is built up from a network of four membered-rings, formed by the vertex linkages between [CoO4] and [H2PO4] tetrahedra with [HPO4] moieties hanging from the Co center. Hydrogen bonds involving the cobalt phosphate units and the triply protonated amine molecule, contribute to the stability of the structure. The IR spectrum shows bands characteristic of the (N4C6H21)3+ cations and the (H2PO4) and (HPO4)2− phosphate anions. The UV-Visible-NIR spectrum confirms the tetrahedral coordination of Co2+ ions. The TGA analysis indicates that the dehydration of (N4C6H21)·(Co(H2PO4)(HPO4)2) occurs in one step. Magnetic measurements from 4.5 to 305 K show a weak antiferromagnetic character of this compound.  相似文献   

8.
Chemical preparation, crystal structure and NMR spectroscopy of a new organic cation 5-chloro(2,4-dimethoxy)anilinium monophosphate H2PO4 are given. This new compound crystallizes in the monoclinic system, with the space group P21/c and the following parameters: a = 5.524(2) Å, b = 9.303(2) Å, c = 23.388(2) Å, β = 90.66(4), V = 1201.8(2) Å3, Z = 4 and Dx = 1.573 g cm−3. Crystal structure has been determined and refined to R = 0.031 and Rw = 0.080 using 1702 independent reflections. Structure can be described as an infinite (H2PO4)nn corrugated chains in the a-direction. The organic groups (5-Cl-2,4-(OCH3)2C6H2NH3)+ are anchored between adjacent polyanions through multiple hydrogen bonds. This compound is also investigated by IR, thermal, and solid-state, 13C, 31P MAS NMR spectroscopies.  相似文献   

9.
NaBi1−xYbx(WO4)2 fibres single crystals were successfully grown by micro-pulling down technology (MPD). The Yb3+-doped NaBi(WO4)2 fibres single crystals have been pulled using MPD technique with controlled diameter and stationary stable growth conditions corresponding to flat crystallization interface with meniscus length equal to the fibre radii and pulling rate range [6-48 mm h−1]. We have determined the monophased field of NaBi1−xYbx(WO4)2 for x ≤ 0.3. The lattices parameters decrease as a function of Yb3+ substitution in Bi3+ sites. The melt behaviour has been study by DTA/TG analysis. We have found that the stoichiometric compounds NaBi(WO4)2 melt congruently at 935 °C. The fibre diameters varied from 0.5 to 1 mm depending on the capillary die diameter, pulling rate and the molten zone temperature. Complementary Yb3+ spectroscopic characterization in the NaBi(WO4)2 lattice has been done by IR emission measurements under laser pumping at room temperature.  相似文献   

10.
The glass formation regions in the system SeO2-Ag2O-B2O3 have been determined using the melt quenching method of evacuated silica ampoules. The structural units forming the amorphous network have been established by IR spectroscopy. The presence of SeO3 (ν = 820 cm−1; 760-750 cm−1), BO3 (ν = 1340, 1270 cm−1) and BO4 (ν = 1050 cm−1) units has been confirmed. Crystallization of Ag2SeO3 only has been observed in a wide concentrate region near the glass formation boundary. A model explaining the unsatisfactory glass formation ability in the system investigated has been developed. It has been suggested that Ag+ ions are predominantly located near the selenite units, which stimulates the formation of isolated SeO3 groups. The transformation of BO3 into BO4 units is hindered by the absence of free Ag+ ions near the borate units.  相似文献   

11.
The present investigation aims to demonstrate the potentiality of Tb3+ and Ce3+ co-doped Ca4Y6(SiO4)6O phosphors. By incorporation of Ce3+ into Ca4Y6(SiO4)6O: Tb3+, the excitation band was extended from short-ultraviolet to near-ultraviolet region. The energy transfer from Ce3+ to Tb3+ in Ca4Y6(SiO4)6O host was investigated and demonstrated to be a resonant type via a dipole–dipole mechanism with the critical distance of 10.2 Å. When excited by 352 nm, Ca4Y6(SiO4)6O: Ce3+, Tb3+ exhibited a brighter and broader violet-blue emission (421 nm) from the Ce3+ and an intense green emission (542 nm) from the Tb3+. Combining the two emissions whose intensities were adjusted by changing the doping levels of the co-activator, an optimized white light with chromaticity coordinates of (0.278, 0.353) is generated in Ca4Y6(SiO4)6O: 2% Ce3+, 8% Tb3+, and this phosphor could be potentially used in near-ultraviolet light-emitting diodes.  相似文献   

12.
A new lithium iron(III) phosphate, Li9Fe7(PO4)10, has been synthesized and is currently under electrochemical evaluation as an anode material for rechargeable lithium-ion battery applications. The sample was prepared via the ion exchange reaction of Cs5K4Fe7(PO4)101 in the 1 M LiNO3 solution under hydrothermal conditions at 200 °C. The fully Li+-exchanged sample Li9Fe7(PO4)102 cannot yet be synthesized by conventional high-temperature, solid-state methods. The parent compound 1 is a member of the Cs9−xKxFe7(PO4)10 series that was previously isolated from a high-temperature (750 °C) reaction employing the eutectic CsCl/KCl molten salt. The polycrystalline solid 1 was first prepared in a stoichiometric reaction via conventional solid-state method then followed by ion exchange giving rise to 2. Both compounds adopt three-dimensional structures that consist of orthogonally interconnected channels where electropositive ions reside. It has been demonstrated that the Cs9−xKxFe7(PO4)10 series possesses versatile ion exchange capabilities with all the monovalent alkali metal and silver cations due to its facile pathways for ion transport. 1 and 2 were subject to electrochemical analysis and preliminary results suggest that the latter can be considered as an anode material. Electrochemical results indicate that Li9Fe7(PO4)10 is reduced below 1 V (vs. Li) to most likely form a Fe(0)/Li3PO4 composite material, which can subsequently be cycled reversibly at relatively low potential. An initial capacity of 250 mAh/g was measured, which is equivalent to the insertion of thirteen Li atoms per Li9+xFe7(PO4)10 (x = 13) during the charge/discharge process (Fe2+ + 2e → Fe0). Furthermore, 2 shows a lower reduction potential (0.9 V), by approximately 200 mV, and much better electrochemical reversibility than iron(III) phosphate, FePO4, highlighting the value of improving the ionic conductivity of the sample.  相似文献   

13.
Thin films of CaWO4 and SrWO4 were prepared on glass substrates by spray pyrolysis. The effects of preparation conditions and monovalent, bivalent and trivalent cation doping on cathodoluminescence (CL) properties of the films were studied. Polycrystalline CaWO4 and SrWO4 films formed a scheelite structure after being annealed above 300°C. They exhibited analogous cathodoluminescence consisting of a blue emission band at 447 nm and a blue-green emission band at 487 nm. The blue and blue-green emission intensities increased with substrate and annealing temperature. Annealing atmosphere and doping with Ag+, Pb2+ and La3+ did not influence the characteristics of the blue and blue-green emissions, whereas Eu3+ did. The results indicated both the blue and blue-green emissions originated from the WO42− molecular complex. The luminance and efficiency for CaWO4 film were 150 cd/m2 and 0.7 lm/W at 5 kV and 57 μA/cm2.  相似文献   

14.
In this work, X-ray diffraction, Raman spectroscopy and differential scanning calorimetry techniques were used to understand the crystallization process on 20Li2O-80TeO2 glass. X-ray diffraction results reveal the presence of three distinct alpha γ-TeO2, α-TeO2 and α-Li2Te2O5 crystalline phases in the glass matrix. The Raman spectroscopy band structure of this glass is similar to the one observed in glassy TeO2. Raman results clearly reveal the metastable character of the γ-TeO2 phase in the 20Li2O-80TeO2 glass, whose associated vibration modes disappear completely at temperatures higher than 315 °C. On the other hand, the Raman modes associated to α-TeO2 and α-Li2Te2O5 phases persists up to temperatures close to the final stages of the crystallization in the studied glass (around 420 °C). From DSC measurements, the activation energies 296 ± 3 and 298 ± 1 kJ mol−1 were associated to γ-TeO2 and α-TeO2 phases crystallization, indicating that these phases crystallizes at temperatures very close in the studied glass.  相似文献   

15.
(C2H10N2)[Mn2.09Co0.91(HPO3)4] has been synthesized using mild hydrothermal conditions under autogeneous pressure. The compound crystallizes in the triclinic P-1 space group. The unit-cell parameters are a = 5.4061(8), b = 5.4150(7), c = 14.136(2) Å, α = 80.84(1), β = 85.41(1), γ = 60.00(1) and Z = 1. The compound shows a layered structure constructed from M3O12 trimer units linked thorough the (HPO3)2− phosphite oxoanions with the ethylenediammonium cations located between the sheets compensating the anionic charge of the inorganic framework. The IR and Raman spectra confirm the presence of the ethylenediammonium cation and phosphite anion. The diffuse reflectance spectrum is in accordance with the presence of Co(II) and Mn(II) high spin cations in slightly distorted octahedral symmetry. The calculated Dq and Racah parameters for the Co(II) cations are Dq = 710, B = 870 and C = 4100 cm−1. The magnetic measurements indicate the existence of antiferromagnetic interactions as the major interactions. Hysteresis observed at low temperature indicates a weak ferromagnetic component, due to a non-cancellation of spins, with coercitive field of 900 G and magnetization of 700 emu/mol.  相似文献   

16.
Tantalum hydrogen phosphate, β-TaH(PO4)2, has a three-dimensional structure that is stable to remarkably high temperature (∼600 °C) presumably due to the presence of strong hydrogen bonds. Impedance measurements indicate a low conductivity, 2.0 × 10−6 S/cm at 200 °C in 5% H2. In further studies aimed at enhancing the conductivity by aliovalent doping, we have investigated systematically the synthesis of compounds in the TaH(PO4)2-W2P2O11 system at 380 °C. As a result, a new phase, Ta2(WO2)0.87H0.26(PO4)4, was identified and subsequently the molybdenum analog Ta2(MoO2)(PO4)4 was also prepared. The structures were determined by single crystal X-ray diffraction techniques. The structures of Ta2(WO2)0.87H0.26(PO4)4 and Ta2(MoO2)(PO4)4 can be formally derived from the structure of β-TaH(PO4)2 by the replacement of two P-OH protons with an MO22+ (M = Mo and W) group together with a change in the orientation of some phosphate tetrahedra.  相似文献   

17.
Crystal structure and ionic conductivity of ruthenium diphosphates, ARu2(P2O7)2 A=Li, Na, and Ag, were investigated. The structure of the Ag compound was determined by single crystal X-ray diffraction techniques. It crystallized in the triclinic space group P−1 with a=4.759(2) Å, b=6.843(2) Å, c=8.063(1) Å, α=90.44(2)°, β=92.80(2)°, γ=104.88(2)°, V=253.4(1) Å3. The host structure of it was composed of RuO6 and P2O7 groups and formed tunnels running along the a-axis, in which Ag+ ions were situated. The ionic conductivities have been measured on pellets of the polycrystalline powders. The Li and Ag compounds showed the conductivities of 1.0×10−4 and 3.5×10−5 S cm−1 at 150 °C, respectively. Magnetic susceptibility measurement of the Ag compound showed that it did not obey the Curie-Weiss law and the effective magnetic moment decreased as temperature decreased due to the large spin-orbital coupling effect of Ru4+ ions.  相似文献   

18.
The organically templated (C4H12N2)[FeIIFeIII(HPO3)2F3] compound has been synthesized under mild solvothermal conditions. The crystal structure has been determined from X-ray single-crystal diffraction data. The compound crystallizes in the P21/n monoclinic space group, with the unit-cell parameters a = 12.935(1), b = 6.4476(7), c = 15.693(2) Å, β = 105.630(9)° and Z = 4. The crystal structure consists of [FeIIFeIII(HPO3)2F3]2− chains formed by a central chain built of [Fe(2)O4F2] edge-sharing octahedra, and two side chains formed by alternating [Fe(1)O3F3] octahedra and [HP(1)O3] tetrahedra. The piperazinium cations are placed between the chains linked by ionic and hydrogen interactions. The IR and Raman spectra show the existence of two phosphite crystallographically independent. From the diffuse reflectance spectrum the Dq parameter for the iron(II) cations has been calculated (Dq = 820 cm−1). The Mössbauer spectrum in the paramagnetic state shows the simultaneous presence of Fe2+ and Fe3+. The magnetic measurements indicate the existence of antiferromagnetic interactions.  相似文献   

19.
Glass systems of the composition xLi2O-20ZnO-(80 − x)B2O3 where (x = 5, 10, 15, 20, 25 and 30 mol%) have been prepared by melt quenching technique. Elastic properties, 11B MAS-NMR and IR spectroscopic studies have been employed to study the structure of Li2O-ZnO-B2O3 glasses. Elastic properties have been investigated using sound velocity measurements at 10 MHz. Elastic moduli reveal trends in their compositional dependence. The bulk modulus and shear modulus increases monotonically with increase of BO4 units, which increase the dimensionality of the network. 11B MAS-NMR and IR spectra show characteristic features of borate network and compositional dependent trends as a function of Li2O/ZnO concentration. The results are discussed in view of borate network and the dual structural role of Zn2+ ions. The results indicate that the Zn2+ are likely to occupy network-forming positions in this glass system.  相似文献   

20.
A series of inorganic phosphate crystals have been hydrothermally synthesized, which have high chemical stability and can keep their crystal structure after acid/base treatments. Its cation-exchange properties have been investigated and the results show that it is an excellent ion exchanger with high exchange capacities for H+, Li+ and Pb2+ ions (12.74, 6.98 and 3.92 mequiv./g, respectively). Selective extractions of Li+ and Pb2+ from the synthetic mixtures containing (Li+, Sr+, K+, Mg2+, Ca2+ and Ba2+) and (Pb2+, Ca2+, Ba2+, Co2+, Ni2+, Zn2+ and Mg2+) have been observed. The reasons of the high exchange selection of NATP for Li+ and Pb2+ ions have been discussed.  相似文献   

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