Secondary ion emission from bismuth under bombardment with Bi m ? and Au m ? cluster ions

The mass spectra of secondary cluster ions Bi _n ⁺ (n = 1–9) from bismuth sputtered by (6–21) keV Au _m ⁻ (m = 1–9) and Bi _m ⁻ (m = 1–5) cluster ions have been investigated. New features of manifestation of dense nonlinear cascades and thermal spikes have been revealed. It is concluded that the thermal spike regime makes a significant contribution to the mechanism of formation of small cluster ions, containing up to seven atoms for a bismuth target.     

Emission of quasi-thermal ions from a solid bombarded by cluster ions

Comparative studies of the emission of quasi-thermal atomic and cluster ions from V, Nb, Ta, Au, and In targets bombarded by cluster ions Au _m ⁻(m = 1–9), as well as from Si and Bi targets bombarded by cluster ions Au _m ⁻(m = 1–9) and Bi _m ⁻(m = 1–5), with energy E ₀ ranging from 6 to 21 keV are carried out. In the case of bombardment by heavy cluster ions, the fraction of the quasi-thermal component in the energy spectra of sputtered atomic ions reaches 50 (for V, In, and Au), 70 (Nb), or more than 90% (Ta). In addition, quasi-thermal ions play a considerable part in the emission of small cluster ions Au₂⁺, In₂⁺, In₃⁺, and Bi _n ⁺(n = 2–7). The results of the generalizing investigation favor the presence of thermal spike conditions at cluster bombardment and their appreciable contribution to the emission of atomic and small cluster ions.     

Polarized Raman and IR spectra of non‐centrosymmetric PbB4O7 single crystal

Polarized Raman and IR spectra of a PbB₄O₇ single crystal were measured. The obtained spectra are discussed within the factor group approach for the orthorhombic P2₁nm(C_2v⁷) space group with Z = 2 assuming that the crystal structure is built up of the (B₄O₇)_∞²⁻ framework and Pb²⁺ ions. It has been shown that vibrations of borate and Pb²⁺ units are observed above 240 and below 160 cm⁻¹, respectively. The results obtained for the spontaneous Raman scattering have also been used in the discussion of the stimulated Raman spectra of the material studied—a new Raman‐laser crystal. The obtained results revealed that mainly translational motions of Pb²⁺ ions participate efficiently in the SRS effect. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman and IR spectra of noncentrosymmetric Bi0.21La0.91Sc2.88(BO3)4 single crystal with the huntite‐type structure

Single crystals of optical nonlinear borate, Bi_0.21La_0.91Sc_2.88(BO₃)₄, were grown and polarized Raman and IR spectra were recorded for this material at room temperature. The spectra have been discussed on the factor group approach for the trigonal R32 (D₃⁷) space group with Z = 3. The assignment of the observed bands to the respective internal and lattice modes is proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

Multiferroic properties of solben gel derived Bi5Fe1-xCoxTi3O15 thin films

Co-doped Bi₅FeTi₃O₁₅ thin films (BFCT-x, Bi₅Fe_1-xCo_xTi₃O₁₅) were prepared using a sol—gel technique. XRD patterns confirm their single phase Aurivillius structure, and the corresponding powder Rietveld analysis indicates the change of space group around x=0.12. The magnetic hysteresis loops are obtained and ferromagnetism is therefore confirmed in BFCT-x thin films. The remanent magnetization (M_r) first increases and reaches the maximum value of 0.42 emu/cm³ at x=0.12 due to the possible Fe³⁺—O—Co³⁺ ferromagnetic coupling. When x = 0.25, the M_r increases again because of the dominant Fe³⁺—O—Co³⁺ ferromagnetic coupling. The remanent polarization (2P_r) of BFCT-0.25 was measured to be as high as 62 μC/cm², a 75% increase when compared with the non-doped BFCT-0 films. The 2P_r remains almost unchanged after being subjected to 5.2 × 10⁹ read/write cycles. Greatly enhanced ferroelectric properties are considered to be associated with decreased leakage current density.     

High-temperature superconductivity in bismuth-copper oxides of the type Bi m M n Cu p O x (M=Mg,Ca, Sr,Ba, Bi)

Several oxides of the Bi _m M _n Cu _p O _x family (m=2, 3;n=2, 3, 4;p=1, 2, 3 and M=alkaline earth or Bi), possessing structures similar to the Aurivillius family of oxides, show highT _c superconductivity. Contribution No. 514 from the Solid State and Structural Chemistry Unit.     

Raman and infrared spectral studies of [C(NH2)3]2MII(H2O)4(SO4)2, MII = Mn,Cd and VO

The Raman and FTIR spectra of three metal guanidinium sulfates, [C(NH₂)₃]₂M^II(H₂O)₄(SO₄)₂, (M^II = Mn, Cd and VO), are recorded. The observed spectral bands are assigned in terms of the fundamental modes of vibration of the guanidinium ions, sulfate groups and water molecules. The appearance of the sulfate tetrahedra's ν₁ and ν₂ modes in the IR spectra and the partial lifting of the ν₄ mode in the Raman spectra indicate the distortion of the SO₄²⁻ tetrahedra in the structure, so that its symmetry is lowered from T_d to C₁. The geometry of the sulfate group in guanidinium vanadyl sulfate does not deviate much from that of the average sulfate group. The distortion of the SO₄ tetrahedra is stronger in GuCds than in GuMnS. The CN₃ group in the guanidinium ion is planar (D_3h point group) in GuCdS and GuMnS, whereas it is lowered in the vanadyl compound. Furthermore, the spectral analyses show the presence of weak hydrogen bonds in the structures. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and phonon properties of nanosized Aurivillius phase of Bi2MoO6

Nanosized crystallites Bi₂MoO₆ of a platelet shape were synthesized by a mild hydrothermal crystallization process. The effect of particle size on the structure and properties of Bi₂MoO₆ was studied by X‐ray diffraction, transmission electron microscopy, as well as Raman and infrared (IR) spectroscopies. Moreover, temperature‐dependent Raman spectra were collected for bulk and nanocrystalline Bi₂MoO₆. These studies showed that the thickness of the smallest crystallites is about 8–11 nm. Raman and IR studies have revealed that the damping and the intensity of Raman and IR bands are significantly modified with decreasing particle size and temperature. Moreover, some bands experience significant shifts both towards lower and higher wavenumbers. The obtained results indicate that, similar to the isostructural Bi₂WO₆, the orthorhombic distortion decreases with decreasing particle size. However, the structure of nanocrystalline Bi₂MoO₆ remains orthorhombic and noncentrosymmetric, and the structural changes are not the same as those observed in Bi₂WO₆. Copyright © 2010 John Wiley & Sons, Ltd.     

Polarised IR and Raman spectra of non‐centrosymmetric Na3Li(MoO4)2· 6H2O crystal—a new Raman laser material

Polarised IR and Raman spectra of Na₃Li(MoO₄)₂· 6H₂O single crystal were measured. Discussion of the results is based on the factor group approach for the trigonal R 3c(C_3v⁶) space group with Z = 2. The assignment of the observed bands was performed on the basis of their polarisation behaviour and literature data. The obtained results for the spontaneous Raman scattering were used in the analysis of the stimulated Raman spectra of the material studied—a new Raman laser crystal. The promoting modes of the stimulated effect were identified. Copyright © 2009 John Wiley & Sons, Ltd.     

Sr位Nd掺杂对SrBi$lt;sub$gt;2$lt;/sub$gt;Nb$lt;sub$gt;2$lt;/sub$gt;O$lt;sub$gt;9$lt;/sub$gt;性能的影响及机理研究

采用传统固相法制备了（Sr_1-3x/2A_x/2Nd_x）Bi₂Nb₂O₉（x=0,0.05,0.1和0.2）陶瓷,并系统研究了Nd离子取代Sr离子对SrBi₂Nb₂O₉性能的影响及其作用机理.研究结果表明：Sr_1-3x/2A_x/2Nd_xBi₂Nb₂O₉的介电常数和介电损耗随温度变化的行为具有明显的离子松弛极化特征.Nd³⁺对Sr²⁺的部分取代,导致Sr_1-3x/2A_x/2Nd_xBi₂Nb₂O₉剩余极化强度P_r稍有下降,但其压电系数d₃₃却有所增加,根据铁电热力学理论,这是Nd³⁺对Sr²⁺取代导致材料介电常数增大所致.Sr_1-3x/2A_x/2Nd_xBi₂Nb₂O₉的居里温度（T_C）没有随Nd含量的增加而变化,拉曼光谱技术分析表明这是其NbO₆八面体畸变程度没有发生变化所致.Nd³⁺取代Sr²⁺提高了材料的介电常数ε_r、压电系数d₃₃、机电耦合系数K_p,同时降低了机械品质因数Q_m,但是谐振频率温度系数C值没有改变. 关键词： 压电陶瓷 介电性能 压电性能 拉曼光谱     

Temperature‐dependent Raman scattering in ferroelectric Bi4−xNdxTi3O12(x = 0, 0.5, 0.85) single crystals

The temperature‐dependent Raman spectra of ferroelectric Bi_4−xNd_xTi₃O₁₂(x = 0, 0.5, 0.85) single crystals were recorded from 100 to 800 K. It was found that there is a critical Nd content x₀ between 0.5 and 0.85. The Nd³⁺ ions prefer to replace Bi³⁺ ions in pseudo‐perovskite layers when x < x₀, while they might begin to incorporate into (Bi₂O₂)²⁺ layers when x ≥ x₀. Nd substitution leads to a decrease in the ferroelectric–paraelectric transition temperature (T_c). A monoclinic distortion of orthorhombic structure occurs in Bi₄Ti₃O₁₂ crystals at temperatures below 200 K. Copyright © 2009 John Wiley & Sons, Ltd.     

Polarized fluorescence spectra analysis of Yb:KGd(WO4)2

The average fluorescence wavelength of the laser crystal is the most important factor in the radiation-balanced laser (RBL). Polarized fluorescence spectra measurements of the anisotropic laser material ytterbium-doped potassium gadolinium tungstate, Yb³⁺:KGd(WO₄)₂, are carried out along principal refractive index directions m, p, g in three configurations in order to achieve the best design for RBL. The average fluorescence wavelength of g polarization is the shortest, so g should be in the face of fluorescence emission; m polarization should be normal to that face to avoid its strong absorption to fluorescence photons. Fluorescence re-absorption causes the average fluorescence wavelength of the directly measured spectra red-shifted at least 9 nm. Methods for depressing radiation trapping are suggested accordingly, which are high power pumping, low doping concentration, small dimensions and fusing with undoped KGd(WO₄)₂.     

Hyperfine interactions in some Aurivillius Bim+1Ti3Fem−3O3m+3 compounds

X-ray diffraction and Mössbauer spectroscopy were applied as complementary methods to investigate the structure and hyperfine interactions in the series of Bi_m+1Ti₃Fe_m−3O_3m+3 Aurivillius compounds with m=4, 6, 7 and 8. Samples were synthesized by the solid-state sintering method at various temperatures. As X-ray diffraction analysis proved, the compounds formed single phases at temperature above 993 K. Mössbauer studies have confirmed diffraction measurements. Compounds synthesized at 993 K contained residual hematite, however these sintered at elevated temperatures were single-phased materials. Room-temperature Mössbauer spectra of Bi_m+1Ti₃Fe_m−3O_3m+3 compounds revealed their paramagnetic properties, what is consistent with the literature data concerning the Néel temperature of these ceramics (T_N is smaller than room temperature). Detailed analysis of MS spectra allowed to state that iron ions may occupy both tetrahedral and octahedral sites in the crystallographic lattice of Aurivillius compounds.     

Raman and IR studies of TaWO5.5, ASbWO6 (A = K,Rb, Cs,Tl), and ASbWO6·H2O (A = H,NH4, Li,Na) pyrochlore oxides

Raman and infrared (IR) spectra of defect pyrochlores TaWO_5.5, NH₄SbWO₆·H₂O, HSbWO₆·H₂O, LiSbWO₆·H₂O, NaSbWO₆·H₂O, KSbWO₆, RbSbWO₆, CsSbWO₆, and TlSbWO₆ were measured. The obtained spectra are discussed using the factor group approach for the cubic Fd‐3m space group, and assignment of bands to respective motions of atoms is proposed. Our results show that the phonon properties of the pyrochlores are strongly affected by disorder, and therefore Raman and IR spectroscopies are very useful tools in studying disorder in this family of compounds. In particular, our studies have shown that in these ionic conductors disorder at sites occupied by NH , H⁺, or alkali‐metal ions decreases with increasing size and mass of these ions. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and photoluminescence properties of MZr2(PO4)3:Eu3+; Bi3+ (M=Na; K) phosphors

A series of new red phosphors, MZr₂(PO₄)₃:Eu³⁺; Bi³⁺ (M=Na; K), were synthesized using the solidstate reaction method, and their photoluminescence spectra were measured. The MZr₂(PO₄)₃:Eu³⁺; Bi³⁺ (M=Na; K) phosphors were efficiently excited by an ultraviolet (UV; 395 nm) source, and showed intense orange-red emission at 595 nm. Further investigation of the concentration-dependent emission spectra indicated that the MZr₂(PO₄)₃:Eu³⁺; Bi³⁺ (M=Na; K) phosphors exhibit the strongest luminescence intensity when y = 0.01 in NaZr_2(0:95−y)(PO₄)₃:Eu_0.10³⁺, Bi_2y ³⁺ and y = 0.09 in NaZr_2(0.95−y)(PO₄)₃:Eu_0.10³⁺, Bi_2y ³⁺, whereas the relative PL intensity decreases with increasing Bi³⁺ concentration due to concentration quenching. The addition of Bi³⁺ widens the excitation band of NaZr_2(0.95−y)(PO₄)₃:Eu_0.10³⁺, Bi_2y ³⁺ around 320 nm, which provides the useful idea of broadening the excitation band around 300–350 nm to fit the ultraviolet chip.     

A lattice dynamical investigation for the Raman and the infrared frequencies of Bi2W2O9

Studies on infrared and Raman-active phonons in the Aurivillius ferroelectric Bi₂W₂O₉ were performed theoretically. The Raman and infrared phonons were calculated by applying a short-range force constant model using normal coordinates having space group Pna2₁. Sixteen stretching, two repulsive and seventeen bending force constants were used for the calculations of the zone center phonons. The calculated Raman and infrared wavenumbers are in very good agreement with the experimental ones in the literature. Potential energy distribution for this compound has also been investigated for the contribution of each force constant towards the Raman and the infrared wavenumbers.     

Effect of Zn substitution on the electrical properties of Bi2Co0.1V0.9O5.35 synthesized by sol-gel method

Samples of Bi₂V_0.9Co_0.1-xZn_xO_5.35, 0.02 ≤ x ≤ 0.08 with layered Aurivillius structure were synthesized successfully by sol-gel citrate method. Structural and electrical characterization of compositions has been investigated by X-ray diffraction, thermogravimetric analysis–differential scanning calorimetric (TGA–DSC) analysis and AC impedance spectroscopy. The tetragonal γ phase has been observed for all investigated samples. The AC impedance response of samples has been measured in the frequency range of 20 Hz to 1 MHz. The impedance for pellets decreases as thermal energy increases. The contribution of grain to the conduction process is more than that of grain boundary. The ionic conductivity and dielectric permittivity are found to be composition-dependent and increase with increasing Zn concentration. The maximum electrical conductivity observed for the composition x = 0.08 is σ = 4.51 × 10^?4 S cm^?1 at 300 °C.     

结合除谱,差谱,二阶差谱的二氯化铜水溶液中直接接触离子对的紫外可见吸收光谱研究

The microstructure of aqueous CuCl₂ has been studied through lots of technologies for many years; however, it remains a controversial subject. In this study, a new spectroscopic method has been proposed to analyze the UV-visible spectra of thin film of CuCl₂/H₂O solutions at different concentrations. This method is the combination of ratio spectra, difference spectra and second order difference spectra. By using this method, two new bands at ~230 and ~380 nm are obviously observed. The bands are assigned as the contacted ion pairs[CuCl₃(H₂O)_n]^- or[CuCl₄(H₂O)_n]^2-, which demonstrates that ion pairs exist in the CuCl₂/H₂O solution. Such finding agrees with the recent theoretical spectra obtained by time-dependent density functional theory. Furthermore, the populations of the contacted ion pairs are discussed. This study not only offers the direct spectroscopic evidence of[CuCl₃(H₂O)_n]^- or[CuCl₄(H₂O)_n]^2- in aqueous CuCl₂, but also suggests that the spectroscopic analysis method is powerful to extract the weak bands in a strong overlapping spectrum.     

Al satellite transition spectroscopy (SATRAS) of polycrystalline aluminium borate 9Al2O3 · 2B2O3

²⁷Al NMR spectra of polycrystalline aluminium borate 9Al₂O₃ · 2B₂O₃ have been measured at 104, 130 and 156 MHz. The parameters of the quadrupole interaction and the isotropic chemical shifts have been obtained by fitting the CT/MAS pattern and consideration of the inner satellite transitions m = 3/2 ↔ 1/2 and m = −1/2 ↔ −3/2. The gain in spectral resolution concerned with the observation of the MAS lines of the inner satellites leads to complete separation of the signals of AlO₆, AlO₅ and AlO₄ polyhedra. Also signals of structural groups of one and the same coordination number can be distinguished. Experimental and theoretical lineshape calculations are compared.     

Raman scattering in A3B2C9 ferroelectric crystals

Raman spectra of some A₃B₂C₉ ferroelectric crystals (here A=Cs, Rb; B=Sb, Bi; C=Br) have been obtained, and a number of high-frequency bands have been assigned. The Rb₃Bi₂Br₉ and Rb₃Sb₂Br₉ crystals are shown to differ in structure from Cs₂Bi₂Br₉. The qualitative changes in the spectra in the 77–300 K temperature interval can be associated not only with structural phase transitions, but with the effect of the anharmonic Fermi resonance between one-and two-phonon excitations as well. Fiz. Tverd. Tela (St. Petersburg) 39, 1452–1455 (August 1997)