非晶态Li+导体分相和晶化过程中的相界效应

非晶态Li⁺导体B₂O₃-0.7Li₂O-0.7LiCl-0.1Al₂O₃在等温处理过程中,其电导率先随时间升高,出现峰值后下降,随后出现两个平台。这是由于材料的分相和晶化所致。本文据相界效应观点,认为不同相之间界面附近有一高电导率层,它对电导率的贡献补偿和超过了由于分相和晶化的体效应所引起的电导率下降。由此,对这种材料的电导率随时间变化曲线给出了解释。 关键词：     

等温热处理过程中一种非晶态Li+导体电导行为的研究

本文在玻璃转变温度以下,采用交流伏安法连续自动观测了非晶态Li⁺导体B₂O₃-0.7Li₂O-0.7LiCl-0.1Al₂O₃在等温热处理条件下的电导行为。结果表明:材料的电导率先随时间升高,出现峰值后单调下降,并含有两个平台部分。与此相配合的DSC与XRD研究证实:形成电导率峰值的基本原因是由于发生了非晶态相分离,而电导率曲线下降部分的平台则是由于非晶态的晶化。最后,从相界 关键词：     

非晶态离子导体Li2B2O4晶化前期的离子导电性

本文研究了非晶态离子导体Li₂B₂O₄的离子电导率与温度的关系,特别着重于晶化前期的离子迁移特性。当温度低于T_K(≈310℃)时,离子电导率遵从Arrhenius关系。当高于晶化温度(≈411℃)时,以晶态中的离子迁移为主。在T_kc时,电导率偏离热激活机制呈反常增高。我们把这一过程称为晶化前期过程。可以用自由体积模型进行描述。晶化前期又可分为两部分:当温度低于、T_p(≈380℃)时,由于自由体积的重新分布,导致了电导率的增高;当T>T_p时,出现了少量微晶,但晶化量小于5%,由于非晶母体与微晶之间的界面效应使得离子导电性显著增强。可以通过室温淬火,把晶化前期非晶态的状态保持到室温,从而有可能制备出离子电导率高于纯非晶态的材料。 关键词：     

流体静高压下的锂离子导电性

本文改进实验方法,在0.0001—1.23GPa流体静高压下测量了整片非晶锂离子导体B₂O₃-0.7Li₂O-0.7LiCl-xAl₂O₃(x=0.05;0.15)及其粉末压片的离子电导率及激活体积。发现粉末压片电导率峰值是由非晶微粒间的接触电导及非晶微粒体电导两者叠加;对整片非晶电导率的压力效应用离子迁移通道的物理图象给出初步的微观解释。此外,还观测到氧化铝组分减少使电导率的压力转变点明显降低;测量出不同温度热处理以及300℃等温热处理4—20h后离子电导率-压力曲线的变化规律,仍可归因于非晶态相分离及两种非晶相的先后晶化。 关键词：     

非晶态离子导体Li2B2O4的核磁共振研究

本文报道了非晶态离子导体Li₂B₂O₄的⁷Li核磁共振研究。测量了⁷Li核磁共振谱与温度的关系。实验中发现,Li₂B₂O₄的晶态、非晶态和部分晶化样品的⁷Li核磁共振谱有很大的不同,且在部分晶化样品的⁷Li核磁共振谱上有附加的小峰,它与LiCl(Al₂O₃)的⁷Li核磁共振谱上附加的小峰相类似。我们也对非晶态离子导体B₂O₃-0.7Li₂O-0.7LiCl进行了⁷Li核磁共振研究,其结果与上面的类似。研究结果表明,它们都起因于非晶母体与微晶的界面效应。 关键词：     

非晶态Li~ 导体分相和晶化过程中的相界效应

非晶态Li~ 导体B_2O_3-0.7Li_2O-0.7LiCl-0.1Al_2O_3在等温处理过程中,其电导率先随时间升高,出现峰值后下降,随后出现两个平台。这是由于材料的分相和晶化所致。本文据相界效应观点,认为不同相之间界面附近有一高电导率层,它对电导率的贡献补偿和超过了由于分相和晶化的体效应所引起的电导率下降。由此,对这种材料的电导率随时间变化曲线给出了解释。     

非晶锂离子导体B2O3-0.7Li2O—0.7LiCl-xAl2O3晶化过程的正电子湮没一维角关联辐射研究

本文用中国第一台正电子湮没辐射一维角关联实验装置,测量了非晶锂离子导体B₂O-0.7Li₂O-0.7LiCl-xAl₂O₃(x=0.15;0.10;0.05)晶化过程中各条正电子湮没辐射的一维角关联曲线,并对归一化的电子动量分布进行了线形参数的计算,从其S参数同样能推测出该离子导体在晶化过程中缺陷浓度的变化。非晶离子导体B₂O₃-0.7Li₂O-0.7LiCl-xAl₂O₃的实验结果表明,Al₂O₃组分不同,对非晶态样品在室温下一维角关联曲线的S参数亦无较大影响。完全晶化后,一维角关联曲线的S参数均有很大下降。在晶化过程最初期,无论Al₂O₃含量多少,S参数都明显略增;到晶化温度附近,仅对Al₂O₃含量较多的非晶,S参数反常增高。这些结果验证和补充了测正电子平均寿命得出的结论。由此初步证实了界面层有大量缺陷的物理图象。 关键词：     

AgI(α-Fe2O3)复合离子导体相转变温度相互影响的研究

通过测量AgI(α-Fe₂O₃)复合离子导体的直流和交流电导率,发现α-Fe₂O₃的Morin转变温度随着AgI含量的增加而降低,电导率测量的结果与磁化率测量和M?ssbauer谱测量结果定性的符合。α-Fe₂O₃也使AgI的α→β相转变温度显著下降。结果表明复合离子导体二相材料各自存在的相转变温度彼此产生影响。 关键词：     

非晶离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3晶化过程的正电子湮没寿命谱和扫描电子显微镜研究

传统的粉末压片样品严重影响了正电子湮没寿命谱及电子显微镜测量的准确性和重复性。本文克服了以上困难,制出大片非晶离子导体样品,得到了晶化过程正电子湮没寿命谱及扫描电子显微镜研究的新结果。非晶离子导体B₂O₃-0.7Li₂O-0.7LiCl-xAl₂O₃的实验结果发现:Al₂O₃组分不同对非晶态样品在室温下的正电子平均寿命无较大影响。完全晶化后,正电子平均寿 关键词：     

Li2O-P205O-V2O5系统非晶材料电学性质与磁共振研究

本文对Li₂O-P₂O₅-V₂O₅系统非晶态中的几组试样进行了电导率、核磁共振及顺磁共振测试。实验分析表明非晶态的log(σΤ)-1/Τ曲线都是由两个直线段构成。电导率在转变温度以后的“晶化前期”异常增大,这归因于该阶段非晶态结构有序化程度增加所致,利用ESR实验结果对非晶态进行钒离子价态分析表明,该系统非晶态中钒离子仅以V⁴⁺和V⁵⁺状态存在。固定P< 关键词：     

PrBa2Cu3O6+x(x=1,0.3)中Pr价态随氧含量的变化

报道了陶瓷和c轴取向薄膜 PrBa₂Cu₃O_6+x(x=1,0.3)材料的红外反射光谱，通过比较区分出该材料的沿着c轴振动和沿着a-b平面振动的声子模，PrBa₂Cu₃O_6+x和RBa₂Cu₃O_6+x(x=1-0,R=Y和稀土元素)有类似的晶体结构，分析和比较它们的声子谱，其中尤其是Pr和Y,Pr和其它稀土元素 关键词：     

PrBa2Cu3O7-δ的制备和电子结构

采用固相反应法制备了正交单相PrBa₂Cu₃O_7-δ样品.运用标准直流四引线法测量了该样品的电阻,发现它随温度的变化呈半导体行为.通过XPS测量表明,样品中明显合有Pr⁴⁺.最后从能带结构讨论了PtBa₂Cu₃0_7-δ不超导的原因. 关键词：     

Mössbauer studies of YBa2Cu3O7−δ-type high-T c superconductors

The local magnetic, electronic, and structural properties of (RE)Ba₂Cu₃O_7?δ supercondcutors (RE=Gd, Dy, and Eu) were studied by Mössbauer spectroscopy using the resonances of¹⁵⁵Gd,¹⁶¹Dy,¹⁵¹Eu, and⁵⁷Eu. In GdBa₂Cu₃O_7?δ, different magnetic ordering behaviors of the Gd sublattice are found for the orthorhombic (superconducting) and tetragonal (non-superconducting) phases. In DyBa₂Cu₃O_7?δ, the magnetic moments of the respective CEF ground states in the orthorhombic and tetragonal phases are derived from paramagnetic hyperfine splittings at 1.4 K. In both DyBa₂Cu₃O_7?δ and EuBa₂Cu₃O_7?δ, anomalies connected with the superconducting transitions in isomer shift, recoil-free fraction, and relaxation behavior were looked for, but not found. The electric-quadrupole splittings observed for both systems are discussed in connection with the lattice EFGs derived for the Gd system. In GdBa₂ (Cu_0.995Fe_0.005)₃O_7?δ, the local properties of the various Fe sites are investigated over a wide temperature range in both the orthorhombic and tetragonal phase. The magnetic ordering of the Gd sublattice in the orthorhombic phase and of the Cu(2) sublattice in the tetragonal phase, respectively, is monitored via the magnetic splittings at the various Fe sites. Possible assignments of Cu(1) and Cu(2) sites as well as different oxygen configurations around the substituted Fe ions are discussed.     

P2O5—Li2O—LiCl-Al2O3系统非晶态离子导体与金属电极间界面阻抗的色散关系

本文研究了非晶态锂离子导体29.6P₂O₅-44.4Li₂O-26.0LiCl和36.3P₂O₅-44.4Li₂O-15.1LiCl-4.2Al₂O₃的阻抗谱,给出了测量盒系统的等效电路,得出了界面阻抗的色散关系。在一定条件下,此界面阻抗过渡到恒相角阻抗。 关键词：     

High temperature study of yttrium--barium--copper oxides near the YBa2Cu3Ox composition by 111In/Cd time differential \gamma--\gamma perturbed angular correlation spectroscopy

The local atomic order around very dilute indium impurities in c-axis-oriented YBa₂Cu₃O₇ and YBa₂Cu₃O_6.25 films at room temperature and in YBa₂Cu₃O_x bulk powders held in air or oxygen over a wide temperature range were investigated using ¹¹¹In/Cd \gamma--\gamma perturbed angular correlation (PAC) spectroscopy. The probe atoms occupy a single substitutional lattice position in YBa₂Cu₃O_x, and evidence reported here strongly supports previous claims that this is the yttrium position. In YBa₂Cu₃O_x powders, the local atomic order changes continuously with temperature. At room temperature the electric field gradient measured by PAC in bulk YBa₂Cu₃O_x powder is indistinguishable from that in the fully oxygenated YBa₂Cu₃O₇ film. Near the decomposition temperature, the bulk YBa₂Cu₃O_x powder data are semiquantitatively similar to data in the room temperature YBa₂Cu₃O_6.25 film, with quantitative differences that we attribute to temperature averaging in the former. Other sites usually found in PAC spectra of YBa₂Cu₃O_x bulk samples arise from ¹¹¹In dissolved in Y₂BaCuO₅ and Y₂Cu₂O₅ impurity phases. The latter phase apparently arises because of significant barium loss during processing; the barium deficiency is clearly demonstrated by comparison of PAC data with the alloy phase diagram above the decomposition temperature. PAC data on pure Y₂Cu₂O₅ are reported here also. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nb(Ba)加强Bi系中2223相生成作用研究

固相法合成系列名义组成为Bi_2-xNb_xSr₂Ca₂Cu₃O_y(x=0—1.0)的样品,电学和磁学测量表明,当掺入x=0.2—0.3的Nb有明显加强2223相生成的作用,配比为Bi_1.7Nb_0.3Sr₂Ca₂Cu₃O_y时最佳;当掺Ba以部分取代Sr后有明显协同Nb促进2223相生成的作用,比单掺Nb效果更为显著,其中以Bi_1.7Nb_0.3Sr_1.8Ba_0.2Ca₂Cu₃O_y为最优组成。热重分析(TGA)实验显示,掺Nb(Ba)后样品在～600°C出现吸氧增重;XPS中的O_1s峰显示掺Nb(Ba)后除～531eV的主峰外,在～529eV的肩峰更加明显;讨论了Nb(Ba)对晶体结构的可能影响。 关键词：     

Comparative studies of the NMR of thulium in Tm123 and Tm124 compounds: Evidence for structural and electronic phase separation

The nuclear magnetic relaxation of ¹⁶⁹Tm in TmBa₂Cu₃O_6+x (x=0.1–1.0, Δ x=0.1) and TmBa₂Cu₄O₈ is studied at temperatures below 5 K. In all the samples, the Tm spin-lattice relaxation proceeds via intrinsic paramagnetic centers (PCs) like Cu²⁺ or copper-oxygen spin-polarized clusters. The experimental data for TmBa₂Cu₃O_6+x support the idea of the structural (chemical) micro-phase separation in oxygen-deficient 123 compounds. Apparently, the samples with x⩾0.4 contain hole-poor nonsuperconducting regions, enriched with PCs, and hole-rich (PC-poor) superconducting regions. The volume fraction f _n of the PC-rich phase reaches a maximum value of 0.85 at x=0.4 and decreases monotonically with increasing x (f _n=0.5, 0.3, and 0.25 at x=0.5, 0.6, and 0.7, respectively). The Tm spin-lattice relaxation in the underdoped TmBa₂Cu₄O₈ compound indicates that this sample, in contrast to oxygen-deficient TmBa₂Cu₃O_6+x , has a homogeneous composition. However, the Tm spin-spin relaxation measurements reveal two sorts of the Tm nuclear spins in Tm124, having different NMR spectra and different relaxation times T ₂. The latter result is evidence of electronic phase separation in CuO₂ phases. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 5, 365–370 (10 September 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Spectroscopic studies of the high-Tc superconducting cuprate perovskites

We present XRD, ESR, IR, DR(UV, VIS) as well as resistivity and magnetic susceptibility data of single phase superconducting perovskites YBa₂Cu₃O_x and EuBa₂Cu₃O_x. A rich phonon structure for both oxide compounds has been observed with a peak at: 72, 108, 135, 148, 172, 570 and 620 cm^-1. The edge of the low energy side was observed at 55 cm^-1. The estimated carrier density for YBa₂Cu₃O_x is (1–2) × 10²¹ cm^-3. A weak ESR signal has also been observed for superconducting phases which is associated with the lattice defects.We also report ESR and optical measurements of constitutent materials as well as not superconducting phases Y₂Cu₂O₅ and BaCuO₂.     

Depth profiles of metal ions implanted in dielectrics at low energies

The depth profiles of Cu⁺, Ag⁺, and Au⁺ ions implanted into amorphous dielectric SiO₂, Al₂O₃, and soda-lime silicate glass (SLSG) are simulated by the DYNA program. The algorithm follows projectile-ion-substrate-atom pair collisions giving rise to a dynamic variation in the phase composition in the surface layer of the irradiated material and takes into account surface sputtering. Ion implantation up to doses of ≤10¹⁶ ion/cm² at low ion energies of 30, 60, and 100 keV is considered. The measured dynamic variation of the depth profiles of implanted ions as a function of the dose is compared with the standard statistical distribution calculated by the TRIM algorithm.     

Magnetic-field-induced transition from metastable spin glass to possible antiferromagnetic-ferromagnetic phase separation in Cd0.5Cu0.5Cr2O4

Using ac susceptibility, dc magnetization and heat-capacity measurements, we have investigated the magnetic properties of Cd_0.5Cu_0.5Cr₂O₄. Cd_0.5Cu_0.5Cr₂O₄ has an extraordinary magnetic phase including a metastable spin-glass (SG) phase at zero field, a possible phase separation scenario of AFM/FM above ∼0.5 T field, and at intermediate fields, an apparent pseudo reentrant spin-glass (RSG) plateau is observed. These phenomena are closely correlated with the pinning effect of the Cu²⁺ sublattice on the frustrated lattice.