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1.
The effect of partial replacement of Cl? ions by Br? ions in the mixed system of ammonium chloride and ammonium bromide during a set of thermal heating cycles is studied. The study includes electrical measurements (d.c. resistivity, dielectric constant and the spontaneous thermal current), differential thermal analysis (DTA) and dilatometric thermal analysis in the temperature range ?60 °C up to 30°C. The results show a large change in the various measured parameters sensitive to thermal agitation process and to the presence of the bromine ions in the mixed crystal system close to the morphotropic boundary x = 0.5. At this boundary the temperature region of the ordered phase extended by about 28°C. The transformation enthalpy was reduced in such case to 41.3 cal/mol. According to the different experimental data of the system NH4BrxCl1-x, a phase diagram was proposed. This phase diagram predicted that the order-disorder phase transition point changed widely according to the value of x and reached ?2°C when the mixed crystal system contained 50% of Br? ions. 相似文献
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The mechanical properties of PbWO4 (PWO) crystals grown by the vertical Bridgman method are systematically investigated using the microindentation technique. In the present work, the Vickers microhardness Hν, fracture toughness Kc, yield strength σy and friability index Bi of PbWO4 crystals are measured. The Vickers microhardness Hν on the (100) wafer is about 140 MPa, which means that PWO is a little soft'' scintillator. The anisotropy of mechanical properties is also investigated under a steady load of 0.5 kg. The (100) wafer of the crystal exhibits combined mechanical properties more excellent than those of (111) and (001) wafers, and the values of Kc, σy, and Bi are 0.538 MPa・m1/2, 51.11 kg/mm2 and 284.96 νm-1/2, respectively. 相似文献
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Sukhorukov Yu. P. Zainullina R. I. Buchkevich A. A. Bebenin N. G. 《Physics of the Solid State》2018,60(9):1844-1847
Physics of the Solid State - The reflection spectra of FeGe2 single crystal in a wide spectral region and in the temperature range from 80 to 310 K are studied. The energy of plasma oscillations,... 相似文献
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We report the growth of ternary half-Heusler MnPtSn single crystals and detailed study on its structural and physical properties.MnPtSn single crystal has a larger lattice parameter than that in polycrystal and it exhibits antiferromagnetism with transition temperature TN at about 215 K,distinctly different from the ferromagnetism of MnPtSn polycrystal.Hall resistivity measurement indicates that the dominant carriers are hole-type and the nearly temperature-independent carrier concentration reac... 相似文献
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Application of piezoelectric resonance enables determination of the complex coefficient s = s ' m is " by means of measurements of the complex admittance. The coefficients s ' and s " can be calculated from the parameters characterising behaviour of the dumped harmonic oscillator in the vicinity of piezoelectric resonance. This method has been used in the determination of phase transition points in a Li 2 B 4 O 7 single crystal. In respect of the temperature dependence of the elastic coefficient $ s_{11}^E $ several anomalies in the range of 20-180°C have been found. In the vicinity of the critical temperatures the imaginary part $ s''^E_{11} $ reveals a more distinct anomaly than the real part $ s'^E_{11} $ . 相似文献
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ZnO单晶材料以其优良的综合性能在光电子器件方面掀起了研究热潮,因此对ZnO单晶的研究具有重要的理论和实践意义。采用激光辐照的方式,对ZnO单晶进行了光致发光(photoluminescence, PL)光谱实验,分析研究了ZnO单晶在不同温度(低温)和不同激光能量强度照射下其光致发光特性。研究结果表明,ZnO单晶内存在少量杂质及表面氧缺陷,这些结构对其发光特性有一定的影响;在低温条件下,ZnO单晶具有良好的发光特性,且随着温度的提高,发光光谱峰的位置会向长波长方向移动,但强度会减小;当激光光源的强度增大,ZnO单晶的PL发射光谱的强度也会随之增大,且峰的位置和相对强度不变。结合拉曼(Raman)光谱实验,从分子及原子振动、转动类型验证了纤锌矿ZnO单晶的六方晶系结构;配合X射线衍射(X-ray diffraction, XRD)技术,得出ZnO单晶良好的结晶特性以及晶轴取向。 相似文献
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The EPR spectra of Cu2+ in Sodium hydrogen oxalate monohydrate, NaHC2O4.H2O(SHOMH hereafter) single crystal was studied at room temperature. The angular variation of EPR spectra showed that the Cu2+ ion in SHOMH single crystal substitutes with Na+ monovalent cation together with a monovalent vacancy to compensate oxygen in the crystal. Since the crystal symmetry is triclinic, only one site is observed in the EPR spectra in three perpendicular axis. The spin Hamiltonian parameters were obtained, and the ground state wave function of Cu2+ ion in the lattice was constructed. 相似文献
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Russian Physics Journal - The paper deals with the grown tin telluride (SnTe) single crystals сontaining extrinsic stacking faults (SFs) and their alloyed ohmic contacts of the... 相似文献
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I. N. Gracheva A. A. Rodionov N. I. Silkin R. V. Yusupov V. B. Dudnikova E. V. Zharikov V. F. Tarasov 《Applied magnetic resonance》2013,44(5):561-570
Vanadium-doped forsterite crystal has been studied with X-band electron paramagnetic resonance (EPR) spectroscopy. The sample was grown by the Czochralski technique in an argon atmosphere with 2 vol% of hydrogen. The EPR spectrum of the sample at T = 15 K is predominantly represented by the V4+ ion signals that possess a characteristic eight-line hyperfine structure and are observed close to g = 2. The observation of the two magnetically nonequivalent centers in the angular dependence in the (ab) crystal plane and one center in the (ac) and (bc) planes, combined with the published optical spectroscopy data, unambiguously show that the V4+ ions are located at the silicon lattice site. Principal values of the hyperfine A and g-tensor and magnetic axes orientations of the V4+ centers have been determined. The orientation disorder of the V4+ centers has been found around the crystalline c axis but not in the (ab) crystal plane. The angular variation of the hyperfine component linewidth is described best with a disorder range of ±3.0°. 相似文献
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提高PbWO4晶体光学性能的研究 总被引:3,自引:2,他引:1
钨酸铅(PbWO4)晶体在生长过程中由于缺氧产生了氧空位缺陷和Fe^2+杂质缺陷,使晶体着色,光学性能下降,在晶体生长过程中掺进Sb2O3,能消除氧空位,将Fe^2+氧化为无色的Fe^3+,较大幅度地提高PbWO4晶体的光学性能和闪烁性能。 相似文献
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Technical Physics - The spectral distribution of photoconductivity and the temperature dependence of photocurrent in MnGaInS4 single crystals have been investigated. Photoconductivity spectra... 相似文献
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Raman Spectroscopy and Magnetic Properties of Mn-Doped ZnO Bulk Single Crystal 总被引:1,自引:0,他引:1 下载免费PDF全文
Mn doped ZnO bulk single crystals are grown by the modified Bridgman method. The as-grown crystals are red in eolour. The additional Raman mode observed at 524cm^-1 is attributed to the Mn ions incorporating into ZnO crystal. The crystal exhibited paramagnetie under lower applied field below 2280 Oe. Then diamagnetism is observed in the crystal when the magnetic field rises up and becomes dominant under applied field above 5270 Oe. The magnetic susceptibility dependence on the temperature follows a Curie law indicating a typical paramagnetie characteristic under an applied field of 2kOe. No ferromagnetic ordering is observed in the as-grown Mn-doped ZnO crystal. 相似文献
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Y. Noda S. Shimono M. Baba J. Yamauchi Y. Uchida N. Ikuma R. Tamura 《Applied magnetic resonance》2008,33(1-2):85-93
Electron paramagnetic resonance study of the single crystals of two PROXYLs, trans-2,5-bis(4-methylphenyl)-2,5-dimethylpyrrolidine-1-oxy [(±)-1] and trans-2-(4-methylphenyl)-2,5-dimethyl-5-phenylpyrrolidine-1-oxy [(±)-2] was conducted. The obtained spectra were always fitted well by a single Lorentzian. The principal g-values (g
x
, g
y
, g
z
) of (±)-1 and (±)-2 were determined as (2.00990, 2.00639, 2.00266) and (2.01106, 2.00742, 2.00389), respectively. The profiles of half width
at half maximum (HWHM) depending on two polar angles, θ and ϕ, were measured in all directions. The angular profiles of the
exchange interaction (|J
0|) were attempted to be estimated by dividing the experimental HWHM by the calculated total second moment (M
2
tot) with the crystallographic data. For (±)-1, |J
0| along the c-axis was estimated to be much larger than that along the a- or b-axis. This suggests that (±)-1 is a one-dimensional magnet along the c-axis.
Authors' address: Yohei Noda, Electron Spin Chemistry Laboratory, Department of Chemistry, Graduate School of Science, Kyoto
University, 606-8502 Kyoto, Japan 相似文献
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在488nFn波长光的激发下,研究了用坩埚下降法生长的掺杂Eu^3 离子的下部与上部LiNbO3晶体从77到600K的变温发射光谱特征。实验结果表明,对于生长后期的上部晶体,随着温度的升高,其发光强度总体增强;然而对于生长初期的下部晶体,随着温度的升高,其发光强度首先增强,到540K时达最大值,然后随着温度的升高,其发光强度反而下降。用热激活效应、声子辅助吸收效应与热猝灭效应解释了晶体上部与下部的发光特征。 相似文献
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采用分子动力学方法模拟含孔洞的单晶铝单轴拉伸过程,研究晶向、孔洞体积分数、空位体积分数等对孔洞生长的影响.结果表明:对于不同的晶向,决定孔洞生长变形的微观机制不同.[010]晶向单轴拉伸情况下,形变机制主要是{111}面位错引起的堆垛层错;[111]晶向单轴拉伸情况下,形变机制主要是位错的移动、堆积与发射.此外,孔洞及空位的体积分数对[010]、[111]晶向的孔洞生长过程也有着明显的影响.总的来说,随着孔洞或者空位体积分数的增加,材料的杨氏模量变小,屈服强度、屈服应变下降. 相似文献
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该文表达了一个研究Yb3+掺杂PbMoO4晶体的光谱和电子顺磁共振谱(EPR)的理论方法. 采用晶体场理论,推导了有关光谱和电子顺磁共振谱的公式. 基于这些理论公式,构建了4f13电子组态在D2d晶体对称下包括Zeeman磁相互作用的14阶能量矩阵. 通过对角化这一能量矩阵,研究了Yb3+掺杂PbMoO4晶体的光谱和电子顺磁共振谱. 所得的理论结果与实验值很好符合. 而且,相关的晶体场参量也在研究中确定. 相似文献