变价元素铋掺杂钨酸铅晶体辐照损伤的研究

采用剂量为4Mrad的γ射线辐照Bridgman法生长的未掺杂和掺铋钨酸铅晶体,研究了辐照前后晶体的透射光谱、X射线激发发射光谱(XSL)的变化.利用正电子湮没寿命谱(PAT)和X光电子能谱(XPS)的实验手段,对钨酸铅晶体辐照前后的微观缺陷进行了研究,并对其抗辐照损伤性能及微观机理进行了初步探讨.研究表明,铋掺杂使得晶体中的正电子捕获中心和低价氧浓度下降;辐照后,未掺杂晶体中正电子捕获中心浓度下降,低价氧浓度上升,掺铋晶体则出现了与之完全相反的情况,正电子捕获中心浓度上升,低价氧浓度下降.提出掺铋钨酸铅晶体中铋的掺杂辐照前主要以Bi³⁺占据VPb的形式存在,辐照使变价元素铋发生Bi³⁺→Bi⁵⁺的变价行为,Bi⁵⁺可以替代W⁶⁺格位并使得晶体内部分(WO₄)^2－根团形成(BiO₃+V_o)^－.     

Ti+(CO2)2Ar和Ti+(CO2)n(n=3-7)络合物离子的红外光解离光谱 (cited: 1)

利用脉冲激光溅射-超声分子束载带方法制备了气相Ti⁺(CO₂)₂Ar和Ti⁺(CO₂)_n(n=3-7)络合物离子．采用红外光解离光谱研究了这些选定的质量离子的振动光谱． 对于每一种络合物离子, 在CO伸缩振动频率范围都观察到了振动峰,表明这些离子具有插入的OTi⁺CO(CO₂)_n-1结构． 对于n≦5的OTi⁺CO(CO₂)_n-1离子,其CO振动和CO₂的反对称伸缩振动频率都比自由的CO和CO₂的频率要高,表明CO和CO₂配体与中心金属离子之间主要是静电相互作用．实验结果还表明TiO⁺可以直接络合五个配体(1个CO和4个CO₂分子)．对于n=2络合物体系,除了插入的OTi⁺CO(CO₂)结构以外,还观察到了具有弯曲结构的OCO-Ti⁺-OCO异构体的存在     

复合层状Bi7Ti4NbO21铁电陶瓷的结构与介电和压电性能研究

制备了Bi₇Ti₄NbO_{21，Bi4Ti3O12及Nb掺杂Bi4Ti3O12(Nb-Bi4Ti3O12)层状结构铁电陶瓷材料.结合Nb-Bi 4Ti3O12的介电温谱和 退极化实验结果，研究了Bi7Ti4NbO21的晶体结构 对其介电、压电性能的影响 .高分辨透射电镜结果表明，在Bi7Ti4NbO21中， 沿着c轴方向，(Bi2Ti3O10)^2-和(BiTiNbO7)^2-两个类钙钛矿层分别 与(Bi2O2)²⁺层叠加堆积而成.这种晶体结构决定了Bi7Ti4NbO21的 介电温谱在668℃和845℃出现介 电双峰.结合极化样品的退化实验分析，说明材料在这两个温度附近发生了铁电—铁电相变 、铁电—顺电相变，分别是(Bi2Ti3O10)^{2-< /sup>和(BiTiNbO7)2-层状 结构发生微观结构相变的结果.在退极化过程中，由于受热时钙钛矿层内空位引起的缺陷偶 极子的定向排列受到破坏，引起材料部分退极化，表现为300℃热处理后Bi7Ti 4NbO 21的压电活性降低了10%，显示了室温下材料的压电性能来源于自发极化的固有电 偶极子和缺陷偶极子的共同贡献.}}     

Resonance Raman Study of Aggregated Meso-tetra(4-pyridinium) porphyrin Diacid

研究了近激子吸收带激发下四-(4-吡啶基)卟啉二酸(H₈TPyP⁶⁺)聚集体的共振拉曼光谱．测量了H₈TPyP⁶⁺单体和聚集体的紫外可见吸收谱和共振光散射光谱．在氘代位移的基础上结合相关体系振动光谱研究,对测得的H₈TPyP⁶⁺)单体和聚集体的拉曼谱带进行了指认．聚集体的形成导致H₈TPyP⁶⁺的卟啉环CC/CN面内伸缩振动向低波数方向位移2～6 cm^-1,而卟啉环鞍形面外振动带向高波数方向位移12cm^-1．基于拉曼谱带的强度和频率变化分析了聚集引起的H₈TPyP⁶⁺分子内结构变化和分子间氢键作用     

FTIR研究快中子辐照直拉硅中的VO2

快中子辐照直拉硅(CZ-Si)经400—450℃热处理后，空位_双氧复合体(VO₂)是其 主要 的缺陷.在300—500℃热处理快中子辐照的CZ_Si后，IR光谱中有919．6cm^-1和 1006cm^-1两个吸收峰伴随VO₂(889cm^-1)出现，这两个IR吸收 峰是VO₂的一种亚稳态缺陷(O-V-O)引起的，此缺陷态是由一个VO(A中心)与次临近的一个 间隙氧原子(O_i)相互作用所形成的.在300℃延长退火时间或升高退火温度，都 会使(O -V-O)转变为稳态VO₂.辐照剂量在10¹⁹数量级，经400—450℃热处 理所形成的缺陷主要为多空位型，而VO₂被抑制.     

四氧杂卟啉二价正离子共振拉曼光谱的TDDFT计算研究

采用DFT/TDDFF计算和极化率的态求和方法研究了四氧杂卟啉二价正离子(TOP²⁺)B态(S₂态)激发的共振拉曼(RR)光谱, 计算模型同时处理了A项和B项对拉曼极化率的贡献.用PBE1PBE、B3LYP、Cam-B3LYP、B3LYP-D3四种交换-相关泛函计算得到的RR光谱总体上相似,其中PBE1PBE和B3LYP 给出的RR 强度与实验吻合得更好一些. 对于全对称振动(A_1g),其拉曼谱带相对强度的理论计算结果与实验一致;TDDFF计算表明： 相对于基态,TOP²⁺的B态沿υ2、υ6、υ7、υ8简正模式有较大的无量纲位移, 导致相应的RR带有较大的强度. 非全对称的B_1g和B_2g 模式通过B项机理增强,其强度比A_1g模式小1～2个量级,与实验结果定性符合. 与实验相比,υ10模式(B_1g)RR强度的理论值过小,而υ11模式(B_1g)的理论值偏大;这可能是由于TOP²⁺的B-态(S₂态)具有Jahn-Teller效应.     

Preparation and Characterization of Storage and Emission Functional Material of Chlorine Anion: [Ca24Al28O64]4+·(Cl-)3.80(O2-)0.10

通过碳酸钙、γ-三氧化二铝、氯化钙在氯气/氩气混合气气氛下的固态反应制备了一种氯负离子存储-发射功能材料[Ca₂₄Al₂₈O₆₄]⁴⁺·(Cl^-)_3.80(O^2-)_0.10(C12A7-Cl^-)．通过离子色谱、电子顺磁共振、拉曼光谱验证,C12A7-Cl^-材料中存储的负离子主要是氯负离子,浓度为(2.21±0.24)×10²¹ cm^-3,此外还有小部分的氧二价负离子、氧负离子、氧分子负离子．这与通过飞行时间质谱得到的结果一致：从C12A7-Cl^-材料表面发射出的负离子主要是氯负离子(大约90%),还有小部分的氧负离子和电子．材料结构和表观变化分别由X射线衍射和场发射扫描电子显微镜表征     

Nd掺杂对Bi4Ti3O12铁电薄膜的微结构和铁电性能的影响

利用溶胶-凝胶法在Pt/Ti/SiO₂/Si(100)衬底上制备了Nd掺杂Bi₄Ti₃O₁₂(Bi_4-xNd_xTi₃O₁₂, x=0.00,0.30,0.45,0.75,0.85,1.00,1.50)铁电薄膜样品.研究了Nd掺杂对Bi₄Ti₃O₁₂薄膜的微结构和铁电性能的影响.研究结果表明:Nd掺杂未改变Bi₄Ti₃O₁₂薄膜的基本晶体结构.在掺杂量x<0.45时,Nd³⁺只取代类钙钛矿层中的A位Bi³⁺.当x=0.45时,样品剩余极化强度达最大值,在270kV·cm^-1的电场下为32.7μC·cm^-2.掺杂量进一步增加时,结构无序度开始明显增大,Nd³⁺开始进入(Bi₂O₂)²⁺层,削弱其绝缘层和空间电荷库的作用,导致材料剩余极化逐渐下降.当掺杂量x达到1.50时,掺杂离子最终破坏(Bi₂O₂)²⁺层的结构,材料发生铁电-顺电相变.     

焙烧温度对SiO2负载的Co3O4纳米粒子表面氧缺陷浓度和CO氧化催化性能的影响

以传统的浸渍法,在不同焙烧温度下制备了用于CO氧化反应的Co₃O₄/SiO₂催化剂．通过激光拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、程序升温还原(TPR)和X射线吸收精细结构谱(XAFS)表征了该系列催化剂的结构．在所有的催化剂中,XRD和Raman光谱都只检测到了Co₃O₄晶相的存在．与Co₃O₄体相相比,XPS结果表明在200 oC焙烧的(Co₃O₄(200)/SiO₂)催化剂中Co₃O₄表面上存在着过量的Co²⁺．与XPS的结果一致,TPR结果表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄表面上存在氧缺陷, 并且XAFS结果也表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄具有更多的Co²⁺．提高焙烧温度使得过量的Co²⁺进一步氧化为Co³⁺,同时降低了表面氧缺陷浓度,从而得到计量比的Co₃O₄4/SiO₂催化剂．在所有的负载催化剂中Co₃O₄(200)/SiO₂催化剂表现出了最好的CO氧化催化性能,表明过量Co²⁺和表面氧缺陷的存在能够促进Co₃O₄催化CO氧化反应的活性.     

He+辐照对Ga0.94Mn0.06As薄膜铁磁性的改善

离子辐照半导体可以很好的改善半导体材料的磁学性质.用He⁺ 辐照Ga_0.94Mn_0.06As薄膜,可以较方便的调制Ga_0.94Mn_0.06As 薄膜中产生铁磁性载体的浓度.由于空穴居间而导致Ga_0.94Mn_0.06As薄膜的铁磁性, 可以通过He⁺的辐照来得到改善,其结果是Ga_0.94Mn_0.06As薄膜的矫顽力可以增加3倍多. 当He⁺辐照流强增加时, 居里温度和沿着样品面外磁化难轴方向的饱和磁场都减小了. 被辐照的Ga_0.94Mn_0.06As薄膜的电学性质和结构特征显示, He⁺辐照Ga_0.94Mn_0.06As薄膜可以有控制地改善它的铁磁性, 其结果源于He⁺辐照Ga_0.94Mn_0.06As薄膜所诱导产生电缺陷对空穴的补偿, 而不是He⁺辐照改变了Ga_0.94Mn_0.06As薄膜的结构.     

Control of Tisurface defect on TiO2 nanocrystal using various calcination atmospheres as the first step for surface defect creation and its application in photocatalysis

A new development to create the surface defect (Ti³⁺) on TiO₂ was reported in this paper and compared to the common methods which must prepare the crystalline TiO₂ in the first step prior, and then create the surface defect in the second step. In this work, the surface defect creation was performed in the first step coinciding with the crystalline TiO₂ preparation using the sol-gel method. The creation was performed by varying the amounts of oxygen fed during calcination. Based on the CO₂-temperature programmed desorption (CO₂-TPD) and electron spin resonance (ESR) results, the surface defect (Ti³⁺) substantially increased with the amount of oxygen fed. Moreover, the samples resulting from calcination were used as photocatalysts for ethylene decomposition. The reactivity of those samples was also discussed.     

Ti<Superscript>3+</Superscript>-doped TiO<Subscript>2</Subscript> hollow sphere with mixed phases of anatase and rutile prepared by dual-frequency atmospheric pressure plasma jet

A novel method of synthesizing Ti³⁺-doped TiO₂ was proposed. Ti³⁺-doped TiO₂ hollow spheres were prepared with different thickness of carbon shell by using atmospheric pressure plasma jet generated by dual-frequency power sources. The as-synthesized Ti³⁺-doped TiO₂ hollow microspheres were characterized by X-ray diffraction (XRD) pattern, scanning electron microscope (SEM) images, high-resolution transmission electron microscopy (HRTEM) images, Raman spectra, X-ray photoelectron spectroscopy (XPS), and UV–vis spectra. These results indicated that these samples had mixed phases of anatase and rutile and the structure of hollow sphere varied with different thickness of carbon shell. The Ti-O-C chemical bond was the connection between the TiO₂ hollow sphere and carbon layer. Amount of Ti³⁺ ions were found, which were accompanied with the formation of oxygen vacancies. Meantime, the as-synthesized catalysts also display strong absorption in the visible light region and have a narrow band energy gap. Optical emission spectroscopy (OES) was used to observe different excited species in the discharge area. These results showed that the oxygen content had a significant impact on the number of oxygen vacancies. Finally, the photocatalytic activities of as-prepared samples were evaluated by decomposition of rhodamine B aqueous solution, which showed better photocatalytic activity under UV–vis light irradiation.     

Defect types and room-temperature ferromagnetism in undoped rutile TiO2 single crystals

Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti3+-V O defect complexes(or clusters) have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti3+ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.     

Spectroscopic studies of interfacial structures of CeO2-TiO2 mixed oxides

We have investigated the geometric and electronic structures of the cerium oxide (CeO₂)-titanium dioxide (TiO₂) mixed oxides with various Ce/TiO₂ weight ratios prepared by the sol-gel method in detail by means of X-ray diffraction (XRD), high-resolution X-ray photoelectron spectroscopy (XPS), Raman spectroscopy excited by 325 and 514.5 nm lasers, and scanning electron microscope (SEM). Existence of cerium effectively inhibits the phase transition of TiO₂ from the anatase phase to the rutile phase. XRD peaks of TiO₂ anatase attenuate continuously with the increasing amount of CeO₂ in the mixed oxide, but the XRD peaks of cubic CeO₂ appear only after the weight ratio of Ce/TiO₂ reaches 0.50. The average crystalline sizes of TiO₂ anatase and cubic CeO₂ in CeO₂-TiO₂ mixed oxides are smaller than those in the corresponding individual TiO₂ anatase and cubic CeO₂. Raman spectroscopy excited by the 514.5 nm laser detects CeO₂ after the weight ratio of Ce/TiO₂ reaches 0.70 whereas Raman spectroscopy excited by the 325 nm laser detects CeO₂ after the weight ratio of Ce/TiO₂ reaches 0.90. XPS results demonstrate that Ti exists in the form of Ti⁴⁺ in the CeO₂-TiO₂ mixed oxide. Ce is completely in the form of Ce³⁺ in the mixed oxides with a 0.05 weight ratio of Ce/TiO₂. With the increasing weight ratio of Ce/TiO₂, Ce⁴⁺ dominates. On basis of these results, we proposed that CeO₂ initially nucleates at the defects (oxygen vacancies) within TiO₂ anatase, forming an interface bridged with oxygen between CeO₂ and TiO₂ anatase. At the interface, Ce species cannot substitute Ti⁴⁺ in the lattice of TiO₂ anatase whereas Ti⁴⁺ can substitute Ce⁴⁺ in the lattice of cubic CeO₂. The decreasing concentration of oxygen vacancies, the Ti-O-Ce interface, and the decreasing average crystalline size of TiO₂ anatase act to inhibit the phase transformation of TiO₂ anatase. With the increasing amounts of CeO₂, the CeO₂ clusters continuously grow and form cubic CeO₂ nanocrystals. Spectroscopic results strongly demonstrate that the surface region of CeO₂-TiO₂ mixed oxide is enriched with TiO₂.     

Growth by laser ablation of Ti-based oxide films with different valency states

x La_2/3+yTiO_3-δ perovskite (with δ≤0.5) were deposited by the laser ablation technique from Li_0.33La_0.56TiO₃ targets. Their growth onto MgO substrateswas studied as a function of the oxygen pressure. For films grown in vacuum (10^-6 mbar), a La_0.63TiO_2.5 composition was obtained, meaning that Ti³⁺ alone is present in the films, while Li ions are not incorporated under these conditions. This material shows good electric conductivity (ρ=500 mΩ cm). By contrast, insulating films with a Li_0.1La_0.70TiO₃ composition corresponding to the Ti⁴⁺ species were obtained at high oxygen pressures (>0.05 mbar). For all conditions, textured films were grown with different orientations depending on the temperature and the oxygen pressure. Received: 10 September 1997/Accepted: 24 November 1997     

A Raman spectroscopic and TEM study on the structural evolution of Na2Ti3O7 during the transition to Na2Ti6O13

The synthesis of sodium hexatitanate from sodium trititanate was characterized by Raman spectroscopy, X‐ray diffraction (XRD) and high‐resolution transmission electron microscopy (HRTEM). The structural evolution from trititanate to hexatitanate was studied using Raman spectra, XRD and HRTEM techniques. It was found that the Raman bands at 279 cm⁻¹ corresponding to very long Ti O bonds and at 883 cm⁻¹ corresponding to the very short Ti O bonds decrease in intensity and finally disappear during the transition from sodium trititanate to sodium hexatitanate. The band at 922 cm⁻¹ corresponding to an intermediate‐length Ti O bond was observed to become stronger with the increase in temperature, indicating that there is no terminal oxygen atom in the crystal structure of Na₂Ti₆O₁₃ and that all the oxygen atoms become linearly coordinated by two titanium atoms. Furthermore, the TiO₆ octahedron in Na₂Ti₆O₁₃ are more regular because the very long (2.2 Å) or very short (1.7 Å) Ti O bonds disappear. It is revealed that the phase transition from trititanate to hexatitanate is a step‐by‐step slipping process of the TiO₆ octahedral slabs with the loss of sodium cations, and a new phase with formula Na_1.5H_0.5Ti₃O₇ has been discovered as an intermediate phase to interlink Na₂Ti₃O₇ and Na₂Ti₆O₁₃. Copyright © 2010 John Wiley & Sons, Ltd.     

Pressure effect on the Raman and photoluminescence spectra of Eu3+-doped Na2Ti6O13 nanorods

Eu³⁺-doped Na₂Ti₆O₁₃ (Na₂Ti₆O₁₃:Eu) nanorods with diameters of 30 nm and lengths 400 nm were synthesized by hydrothermal and heat treatment methods. Raman spectra at ambient conditions indicated a pure monoclinic phase (space group C2/m) of the nanorods. The relations between structural and optical properties of Na₂Ti₆O₁₃:Eu nanorods under high pressures were obtained by photoluminescence and Raman spectra. Two structural transition points at 1.39 and 15.48 GPa were observed when the samples were pressurized. The first transition point was attributed to the crystalline structural distortion. The later transition point was the result of pressure-induced amorphization, and the high-density amorphous (HDA) phase formed after 15.48 GPa was structurally related to the monoclinic baddeleyite structured TiO₂ (P2₁/c). However, the site symmetry of the local environment around the Eu³⁺ ions in Na₂Ti₆O₁₃ increased with the rising pressure. These above results indicate the occurrence of short-range order for the local asymmetry around the Eu³⁺ ions and long-range disorder for the crystalline structure of Na₂Ti₆O₁₃:Eu nanorods by applying pressure. After releasing the pressure from 22.74 GPa, the HDA phase is transformed to low-density amorphous form, which is attributed to be structurally related to the α-PbO₂-type TiO₂.     

Sulfonated poly(phenylene oxide)/Ti<Superscript>3+</Superscript>/TiO<Subscript>2</Subscript> nanotube arrays membrane/electrode with high performances for lithium ion battery

Sulfonated poly(phenylene oxide) (SPPO) film was electrodeposited on Ti³⁺-doped TiO₂ nanotube arrays (Ti³⁺/TiO₂NT) electrode via the electropolymerization of sulfonated phenol. The as-synthesized SPPO/Ti³⁺/TiO₂NT membrane/electrode was investigated in terms of SEM, FESEM, EDX, FTIR, XPS, galvanostatic charge/discharge, and cycle voltammetry (CV). As expected, the porous SPPO film did form on the surface of Ti³⁺/TiO₂NT electrode; furthermore, the resultant SPPO/Ti³⁺/TiO₂NT membrane/electrode delivered higher electrochemical performances than PPO/Ti³⁺/TiO₂NT, mainly attributed to the contributions of the ionic conductivity induced by –SO₃H groups within SPPO.     

Surface state of TiO2 treated with low ion energy plasma

The effect of low pressure radio frequency (rf) plasma treatment on TiO₂ surface states has been studied using X-ray photoelectron spectroscopy. Three different oxidation states of oxygen in untreated TiO₂ powder were observed, which suggests the existence of adsorbed water and carbon on the surface. The ratio of oxygen to titanium (O/Ti) was decreased for the low ion dose plasma treated samples due to desorption of water from the surface. In the case of Ti 2p about 20% of surface states were converted to Ti³⁺ 2p_3/2 state after plasma treatment with a very good stability, whereas untreated TiO₂ remained mostly as Ti⁴⁺ state. A rapid decrease in the ratio of carbon to titanium (C/Ti) at TiO₂ surface was also observed after plasma treatment and more than 90% of carbon atoms were removed from the surface. Therefore, the plasma treatment of TiO₂ has advantages to surface carbon cleaning, increasing O⁻ and Ti³⁺ surface states, hence improving the activity of TiO₂ for different environmental, energy and biological applications.     

Bifunctional photocatalysis of TiO2/Cu2O composite under visible light: Ti in organic pollutant degradation and water splitting

Photocatalytic experiment results under visible light demonstrate that both TiO₂ and Cu₂O have low activity for brilliant red X-3B degradation and neither can produce H₂ from water splitting. In comparison, TiO₂/Cu₂O composite can do the both efficiently. Further investigation shows that the formation of Ti³⁺ under visible light has great contribution. The mechanism of photocatalytic reaction is proposed based on energy band theory and experimental results. The photogenerated electrons from Cu₂O were captured by Ti⁴⁺ ions in TiO₂ and Ti⁴⁺ ions were further reduced to Ti³⁺ ions. Thus, the photogenerated electrons were stored in Ti³⁺ ions as the form of energy. These electrons trapped in Ti³⁺ can be released if a suitable electron acceptor is present. So, the electrons can be transferred to the interface between the composite and solution to participate in photocatalytic reaction. XPS spectra of TiO₂/Cu₂O composite before and after visible light irradiation were carried out and provided evidence for the presence of Ti³⁺. The image of high-resolution transmission electron microscopy demonstrates that TiO₂ combines with Cu₂O tightly. So, the photogenerated electrons can be transferred from Cu₂O to TiO₂.