Temperature dependence of quadrupole interaction of99Ru in Zn

The quadrupole interaction (QI) of⁹⁹Ru as a dilute impurity in Zn, Cd and Sn lattices was studied by using time differential perturbed angular correlation technique. The electric field gradients calculated from the measured quadrupole interaction frequencies at room temperature are 5.14 × 10¹⁷ volts/cm² for⁹⁹RuZn, 4.58 × 10¹⁷ volts/cm² for⁹⁹RuCd and 2.87 × 10⁹⁹ volts/cm² for⁹⁹RuSn. The temperature dependence of the QI studied in the case⁹⁹RuZn is similar to that of¹¹⁷InZn.     

Magnetization,AC susceptibility and microwave absorption in Tb and Gd70Tb30

Measurements of magnetization, ac susceptibility and microwave absorption at 9.5 and 35 GHz, have been carried out with single crystals of Tb and Gd₇₀Tb₃₀. The critical temperatures for Tb were in agreement with previous published results. The Curie Temperature for Gd₇₀Tb₃₀ was measured to be (275 ± 2) K. Anisotropy constants have been derived from the microwave measurements. The value of K₂ at 0 K is estimated to 8.8 × 10⁸ erg cm^-3 (Tb) and 1.3 × 10⁸ erg cm^-3 (Gd₇₀Tb₃₀). At 77 K, the value of K₆ is estimated to be 6 × 10⁴ erg cm^-3 (Gd₇₀Tb₃₀.     

Electric field gradients at Os nuclei in the hexagonal transition metals Os and Re

The electric field gradient eq at Os nuclei in Os and Re single crystals has been determined by Mössbauer transmission experiments with the 137 keV resonance in ¹⁸⁶Os as -4.5 (3) × 10¹⁷ V/cm² and - 3.8 (3) × 10¹⁷ V/cm², respectively.     

The electric field gradient at 57Fe in zinc and comparisons with the conduction-electron charge-shift model

The magnitude of the electric field gradient at ⁵⁷Fe probe nuclei in Zn is measured using Mössbauer effect and the value is 2.34 × 10¹⁷ V/cm². The electric field gradients at Fe probe nuclei in Ti, Zn, Zr, Cd and Hf hosts are compared with the predictions of the conduction-electron charge-shift model.     

Quadrupole interaction of tantalum impurities in bismuth metal

The time differential perturbed angular correlation technique has been used in the measurement of the electric quadrupole interaction of Ta impuritiy in bismuth metal. The interaction frequencies at 293, 400 and 500 K have been observed to be 288±1.5, 266.9±3 and 244.5±4.3 MHz respectively. The electric field gradient at 293 K is 4.75±0.3 × 10¹⁷ V/cm² with the temperature coefficientB=2.2±0.2 × 10⁻⁵ (K)^−3/2.     

The electric field gradient at tantalum in yttrium

A uniform, axially symmetric electric field gradient at ¹⁸¹Ta in hcp Y of |eq| = (5.9 ± 0.3) × 10¹⁷V/cm² at 300 K, increasing by 11% upon cooling to 4.2 K, was found using the time differential perturbed angular correlation technique.     

Static electric quadrupole interaction of Ta- and Hf-ions in barium and lead titanate

The static electric quadrupole interaction of¹⁸¹Ta and¹⁷⁸Hf in polycrystalline barium and lead titanate at the site of titanium has been measured using time differential PAC and the Mössbauer effect. The electric field gradients (EFG) at room temperature at the¹⁸¹Ta nucleus are ¦V _zz¦=(3.6±0.2)·10¹⁷V/cm² in BaTiO₃ and ¦V _zz¦=(14.6±0.6)·10¹⁷ V/cm² in PbTiO₃. The temperature dependence of the quadrupole interaction has been studied giving the following EFG values: ¦V _zz¦=(2.4±0.2)·10¹⁷ V/cm² in the monoclinic and ¦V _zz¦=(1.1±0.3)·10¹⁷ V/cm² in the rhomboedral phase of BaTiO₃, and ¦V _zz¦=(15.7±0.6)·10¹⁷ V/cm² for¹⁸¹Ta/PbTiO ₃ at 77 °K. The EFG of¹⁷⁸Hf in PbTiO₃ has been derived from a Mössbauer effect experiment to beV _zz=+(10.7±0.5)·10¹⁷ V/cm². The results are compared with EFG's calculated in a point charge model and with experimental EFG's measured at⁴⁴Sc and⁵⁷Fe in the same titanates by other authors. Contributions of covalent bonds to the effective EFG's in perovskit crystals are discussed.     

Sign of the electric field gradient at111Cd in Zr and Sb

The Β-γ TDPAC technique was applied to¹¹¹Ag implanted in Zr and Sb metal single crystals in order to determine sign and magnitude of the quadrupole interaction at the site of¹¹¹Cd in these metals. An analysis of the data taken at 293K yielded Ν_Q=+15.4(6) MHz for¹¹¹Cd in Zr and Ν_Q=?107.5(20) MHz for¹¹¹Cd in Sb. From these values electric field gradients of +7.3(8)×10¹⁶ V/cm² and ?5.56(62)×10¹⁷ V/cm² for Cd in Zr and Sb are derived respectively.     

Energy transfer and photoextinction from Ln to Tb and Eu in aqueous chloride solutions

Energy transfer and photoextinction from Ln³⁺ to Tb³⁺ and Eu³⁺ in aqueous chloride solutions were studied by absorption, emission and excitation spectra. The energy gaps below the luminescent terms of Gd³⁺, Tb³⁺ and Eu³⁺ are spanned by 10, 5 and 4 quanta, respectively, of the highest energy vibration in aqueous solution, and luminescence is observed in each case. This is not so for other Ln³⁺ where nonradiative deactivation dominates over luminescence. It was verified that only Gd³⁺ could transfer energy to Tb³⁺ and Eu³⁺ ions in aqueous or acid solutions. The ions Pr³⁺, Nd³⁺, Sm³⁺, Dy³⁺, Ho³⁺ and Er³⁺ exhibited strong competitive absorption at certain wavelengths, resulting in the photoextinction of Tb³⁺ and Eu³⁺ emission.     

The low temperature quadrupole orientation of103Ru in ruthenium

The quadrupole frequencyv _Q =e ² qQ/h of¹⁰³Ru (Z=44,N=59) in a ruthenium single crystal has been measured using the technique of low temperature quadrupole orientation to bev _Q (¹⁰³RuRu)=−14.7(5) MHz. Temperatures below 2 mK were reached in this experiment using a PrNi₅ demagnetization stage attached to a³He−⁴He dilution refrigerator. Using the measured magnitude of the RuRu electric field gradient (EFG) at low temperatures |eq(RuRu)|=1.02(3)×10¹⁷ V.cm⁻² [1] and adopting the sign ofeq(RuRu) to be negative from systematics, this result yields a value for the ground-state electric quadrupole moment of¹⁰³Ru ofQ(¹⁰³Ru)=+0.59(2) b. This moment may be interpreted using the weak coupling model of de-Shalit [2]. A Korringa constant for¹⁰³RuRu ofC _K=39(6) Ks was measured in this experiment. Taking advantage of a small iridium contamination of the ruthenium single crystal, the quadrupole moment of the¹⁹²Ir ground state was determined to beQ(¹⁹²Ir)=+2.12(25) b. The sign of the IrRu electric field gradient was found to be negative as a result of this work.     

The electric field gradient and its temperature dependence for ruthenium in scandium and yttrium

The electric field gradients (EFG) for ruthenium in scandium and yttrium metal were determined by TDPAC measurements to be 19(4) × 10¹⁷ V/cm² and 5.5(12) × 10¹⁷ V/cm² respectively at room temperature. The EFG for Ru in Sc was found to vary considerably in the temperature range from 14 to 700 K, whereas for Ru in Y only an extremely small temperature dependence of the EFG was observed.     

Magnetic properties of some gadolinium—Cobalt intermetallic compounds

Crystallographic and magnetic properties of the single crystals having the compositions of GdCo₃, Gd₂Co₇, GdCo₅, Gd_2.2Co_16.6 and Gd₂Co₁₇ were studied in order to contribute to the investigation of the magnetic anisotropy in the Gd–Co system. The single crystal used were prepared by means of the Bridgman method using BN-coated alumina crucibles.The room-temperature magnetocrystalline anisotropy constants K₁ of GdCo₃, Gd₂Co₇, GdCo₅, Gd_2.2Co_16.6 and Gd₂Co₁₇ are determined as 8.1 × 10⁶, 1.3 × 10⁷, 4.1 × 10⁷, 3.0 × 10⁶ and -2.7 × 10⁶ erg/cm³, respectively. it is also found that the magnetocrystalline anisotropy of Gd–Co phases in the stable region of the Th₂Zn₁₇-type structure changes very sensitively from negative to positive as the ratio Gd/Co increases above the stoichiometric ratio of 2/17.     

Quadrupole interaction at181Ta in selenium

The nuclear quadrupole interaction of Ta-181 in selenium was measured using perturbed angular correlation technique. The electric field gradient at room temperature is 4.56(32) × 10¹⁷ V/cm². The temperature dependence of EFG follows the usual T^3/2 behaviour.     

Anomalously high photovoltages in terbium molybdate

In terbium molybdate Tb₂(MoO₄)₃ at room temperature, a laser beam of wavelength λ ₁=4880 Å induces an electric polarization that lasts for several days after the irradiation is turned off. The photoinduced polarization has the same sign as the spontaneous polarization. At a laser power of 0.5 W and an exposure time of 4.5 h, the photoinduced polarization exceeds the spontaneous polarization by an order of magnitude. The corresponding electric field is 2.5×10⁶ V/cm. Under the influence of radiation with λ ₁=4880 Å, terbium molybdate luminesces in the green part of the spectrum near λ ₂≈5425 Å. The luminescence quantum yield is 20%.     

Über Elektronendriftbeweglichkeit und Stoßionisierung in KBr-Kristallen bei hohen elektrischen Feldstärken

A swarm of electrons passing a KBr-crystal has been investigated by fast oscilloscopic techniques at high electric fields (3×10⁴ to 4×10⁵ V/cm). From the temporal current shape we determined the electron drift mobilityμ=15±2 cm²/Vsec, the electron life timeτ=2±0.3 × 10^?7 sec and the multiplication factor. From this measurement the ionization coefficientα for electrons was calculated as a function of the applied electric field.     

A novel high-voltage light punch-through carrier stored trench bipolar transistor with buried p-layer

A novel high-voltage light punch-through(LPT) carrier stored trench bipolar transistor(CSTBT) with buried p-layer(BP) is proposed in this paper.Since the negative charges in the BP layer modulate the bulk electric field distribution,the electric field peaks both at the junction of the p base/n-type carrier stored(N-CS) layer and the corners of the trench gates are reduced,and new electric field peaks appear at the junction of the BP layer/N drift region.As a result,the overall electric field in the N drift region is enhanced and the proposed structure improves the breakdown voltage(BV) significantly compared with the LPT CSTBT.Furthermore,the proposed structure breaks the limitation of the doping concentration of the N-CS layer(NN CS) to the BV,and hence a higher NN CS can be used for the proposed LPT BP-CSTBT structure and a lower on-state voltage drop(Vce(sat)) can be obtained with almost constant BV.The results show that with a BP layer doping concentration of NBP = 7 × 1015 cm-3,a thickness of LBP = 2.5 μm,and a width of WBP = 5 μm,the BV of the proposed LPT BP-CSTBT increases from 1859 V to 1862 V,with NN CS increasing from 5 × 1015 cm-3 to 2.5 × 1016 cm-3.However,with the same N-drift region thickness of 150 μm and NN CS,the BV of the CSTBT decreases from 1598 V to 247 V.Meanwhile,the Vce(sat) of the proposed LPT BP-CSTBT structure decreases from 1.78 V to 1.45 V with NN CS increasing from 5 × 1015 cm-3 to 2.5 × 1016 cm-3.     

CHCl3电子吸附速率常数的离子迁移谱

利用电晕放电离子迁移谱, 使用高纯氮气作为载气和迁移气体, 研究了电场强度在200～500 V/cm变化时CHCl₃的解离电子吸附速率常数, 得到样品所对应的电子吸附速率常数为1.26×10^-8～8.24×10^-9 cm³/(molecules s)．利用该装置测量了固定电场下,样品的电子吸附速率常数与样品浓度之间的关系．此外利用所获得的离子迁移谱图得到了不同电场强度下Cl^-与CHCl₃之间的离子分子反应速率常数.     

Sn离子注入PbTe的热电性能和结构

对碲化铅(PbTe)在室温下进行了Sn离子注入(200keV,6×10¹⁶和1×10¹⁷ion/cm²).应用电学和热学测量、X射线衍射技术(XRD)和X射线光电子能谱(XPS)研究了Sn离子注入PbTe的热电性能和注入层结构. 关键词：     

Electric field gradients at 181Ta probe in ZrNi: Results from perturbed angular correlation and first-principles calculations

Results of temperature dependent perturbed angular correlation (PAC) measurements in the equiatomic ZrNi alloy have been reported for the first time using ¹⁸¹Hf probe. At room temperature, values of quadrupole frequency and asymmetry parameter for the major component (~80%) are found to be ω_Q=26.8(4) Mrad/s, and η=0.413(7). The resulting electric field gradient comes out to be V_zz=2.99 ×10¹⁷ V/cm² and this corresponds to the probe nuclei occupying the regular substitutional Zr sites. In ZrNi system, no magnetic interaction is observed down to 77 K indicating absence of any magnetism in this material. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies on an inactive but similarly prepared sample confirm the dominant presence of the orthorhombic ZrNi phase in the sample. A complementary density functional theory (DFT) calculation results in V_zz=−2.35×10¹⁷ V/cm², η=0.46 at the ¹⁸¹Ta probe impurity site and zero magnetic moment on each atomic site, in close agreement with the experimental results. Furthermore, it is found that electric field gradient for the regular component follows a T^3/2 temperature dependence between 77 and 353 K, beyond which it varies linearly with temperature.     

Analysis of the charge transfer mechanisms responsible for the current-voltage characteristics of Ca<Subscript>4</Subscript>Ga<Subscript>2</Subscript>S<Subscript>7</Subscript>: Eu<Superscript>3+</Superscript> single crystals

The current-voltage characteristics of Ca₄Ga₂S₇: Eu³⁺ single crystals are measured for the first time, and the processes affecting these characteristics are analyzed theoretically. It is demonstrated that Ca₄Ga₂S₇: Eu³⁺ single crystals are high-resistance semiconductors with a resistivity of ～10⁹ Ω cm and a relative permittivity of 10.55. The electrical properties of the studied materials are governed by traps with activation energies of 0.13 and 0.19 eV and a density ranging from 9.5×10¹⁴ to 2.7×10¹⁵ cm^?3. The one-carrier injection is observed in weak electric fields. In electric fields with a strength of more than 4×10³ V/cm, traps undergo thermal field ionization according to the Pool-Frenkel mechanism. At low temperatures and strong fields (160 K and 5×10⁴ V/cm), the electric current is most likely due to hopping conduction by charge carriers over local levels in the band gap in the vicinity of the Fermi level.