铌酸钾锂铁电薄膜的脉冲激光沉积与光学性能

以K2CO3、Li2CO3和Nb2O5为原料,采用固相反应法制备了铌酸钾锂陶瓷;以此为靶材,采用脉冲激光沉积技术在石英玻璃上沉积了铌酸钾锂薄膜,系统研究了沉积温度对铌酸钾锂薄膜组成与结构的影响.利用X射线衍射、拉曼光谱等测试手段对薄膜的结构进行表征,通过紫外一可见光分光光度计测试薄膜的光学透过率.结果表明:所制备的铌酸钾锂靶材结构致密;在衬底温度为700℃、氧分压10 Pa的条件下可以制备纯的铌酸钾锂薄膜,所得到的多晶薄膜呈(310)取向;光学性能测试显示所制备的铌酸钾锂薄膜在可见光范围内的光学透过率为90;左右.     

助熔剂坩埚下降法生长近化学计量比Co:LiNbO3晶体

以K2O为助熔剂,在较大的温度梯度(90～100℃/cm)条件下进行引种和晶体生长,应用坩埚下降法成功地生长出了初始CO2+掺杂浓度为0.5mol;的近化学计量比的铌酸锂晶体.测定了该晶体的红外光谱与吸收光谱,与同成份的LiNbO3晶体相比,其紫外吸收边向短波方向移动,OH-红外吸收峰的位置发生变化.观测到520,549,612nm三个分裂的尖吸收峰以及1400nm左右为发光中心的吸收带.从吸收特性可以判断,Co离子在铌酸锂晶体中呈现+2价.比较上部与下部晶体的吸收强度,可以推测出沿着晶体生长方向Co2+离子浓度逐渐降低,Co2+离子在晶体中有效的分凝系数大于1.     

高温下锂离子在低掺镁铌酸锂晶体中的扩散

研究了高温富锂气氛下锂离子在低掺镁铌酸锂晶体中的扩散.采用气相输运平衡法制备了掺杂1mol; MgO的不同锂含量的铌酸锂(Mg1LN)晶体,采用热分析仪测试了晶体的居里温度.制备了一系列不同锂含量的Mg1LN多晶料,拟合了晶体锂含量与居里温度的关系.采用Boltzmann-Matano法求解了扩散方程.结果表明,扩散温度为1100 ℃时,Mg1LN晶体中锂离子扩散系数为3.2×10-9~13.0×10-9 cm2/s,当扩散温度为1145 ℃时锂离子扩散系数约是1100 ℃时扩散系数的三倍.因此,适当提高扩散温度是提高气相输运平衡法制备近化学计量比低掺镁铌酸锂晶体效率的有效办法.     

共沉淀法制备富锂正极材料Li[Li0.2Mn0.54Ni0.13Co0.13]O2及其电化学性能的研究

采用共沉淀法合成富锂正极材料Li[Li0.2Mn0.54Ni0.13Co0.13]O2.研究了合成时间、配锂量、焙烧温度及焙烧时间对正极材料电化学性能的影响.研究结果表明在60℃下,合成时间为6h时制备的Li[Li0.2Mn0.54Ni0.13Co0.13]O2材料具有较高的振实密度和较好的电化学性能.配锂量不仅会影响材料的结构,同时对材料的电化学性能也有一定的影响.研究显示当Li/M(nLi/nM(M=Ni+Co+Mn))为1.25/0.8时,制备材料的首次放电比容量最高.焙烧温度和焙烧时间对Li[Li0.2Mn0.54 Ni0.13Co0.13]O2的电化学性能影响很大,焙烧温度为900℃,焙烧时间为15 h得到材料的电化学性能最优.     

水热反应温度对CaTi2O4(OH)2粉体微观形貌与紫外光催化性能的影响

以钛酸正丁酯和无水氯化钙为原料,采用水热法制备了不同紫外光催化特性的CaTi2O4(OH)2粉体.利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对样品的相结构和微观形貌进行了分析,并结合粉体的紫外-可见吸收分光光谱表征了材料的吸收特性及带隙宽度.研究了不同水热反应温度对CaTi2O4(OH)2物相结构、微观形貌、晶体生长特性及紫外光催化性能的影响.结果表明:水热反应温度控制在160~200 ℃时,保温36 h都能得到纯的CaTi2O4(OH)2相,粉体的形貌随着水热反应温度的提高经历了由片状和颗粒垛堆到发育成完整的片状形貌过程,当水热反应温度在200 ℃时,片与片之间出现积聚现象;在水热反应温度为180 ℃时,制备的粉体具有最高的结晶度,在紫外光5 h下对罗丹明B的催化效率最佳.     

提拉法生长大尺寸γ-LiAlO2单晶的研究

由于与GaN晶格失配小(约1.4%),γ-LiAlO2单晶有望成为一种很有希望的CaN外延衬底材料.本文使用提拉法生长出了尺寸达φ45×50mm3的γ-LiAlO2单晶.对该晶体毛坯的各个有代表性的位置作了X射线粉末衍射(XRPD)分析,结果表明仅仅在晶体毛坯的底部生成了一种缺锂相(LiAl5O8).γ-LiAlO2晶体化学稳定性差,在室温时轻微水解.当在空气中于1100℃退火70h,γ-LiAlO2晶体挥发出锂组分,在表面产生缺锂相(LiAl5O8).值得注意的是,在γ-LiAlO2晶体的红外光谱区不存在氢氧根吸收带.     

不同硫化温度对Cu2ZnSnS4薄膜质量及太阳能电池性能的影响

采用ZnS-Sn-CuS作为靶材,利用磁控溅射技术制备了Cu2ZnSnS4 (CZST)薄膜材料及太阳电池,重点研究了不同硫化温度对CZTS薄膜质量及太阳电池性能的影响.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、显微拉曼光谱仪(Raman)和紫外可见分光光度计(UV-Vis)分别表征了不同硫化温度下制备的CZTS薄膜的晶相结构、表面形貌、化学组分、相的纯度和光学性能.结果表明:在580℃下所制备的CZTS薄膜光滑致密、结晶质量好,同时化学组分属于贫铜富锌,而且无其他二次相,禁带宽度约为1.5 eV.符合高效率太阳电池吸收层的要求.将CZTS吸收层按照SLG/Mo/CZTS/CdS/i-ZnO/ITO/ Al的结构制备成面积为0.12 cm2的电池并进行Ⅰ-Ⅴ测试.测试结果表明,在580℃硫化后制备的CZTS薄膜太阳电池具有最高的转换效率为3.59;.     

四价掺杂铌酸锂晶体抗光折变性能研究

我们在同成份铌酸锂晶体中掺入四价离子铪,生长了掺杂浓度分别为2、4、6mol;的掺铪铌酸锂系列晶体.掺铪浓度达到4mol;时,晶体的抗光损伤能力为5×105W/cm2,比同成份纯铌酸锂晶体提高了4个数量级.应用全息法测得掺4、6mol;铪的铌酸锂晶体最大折射率变化为8.7×10-6,与高掺镁(6.5mol;)铌酸锂晶体的类似.晶体的红外吸收谱和紫外-可见光吸收谱也显示,掺杂浓度为4mol;时具有明显的阈值特征.由此可以确定铪离子在铌酸锂晶体中的阈值浓度约为4mol;.     

高温下锂离子在低掺镁铌酸锂晶体中的扩散（英文）

研究了高温富锂气氛下锂离子在低掺镁铌酸锂晶体中的扩散。采用气相输运平衡法制备了掺杂1mol%MgO的不同锂含量的铌酸锂(Mg1LN)晶体,采用热分析仪测试了晶体的居里温度。制备了一系列不同锂含量的Mg1LN多晶料,拟合了晶体锂含量与居里温度的关系。采用Boltzmann-Matano法求解了扩散方程。结果表明,扩散温度为1100℃时,Mg1LN晶体中锂离子扩散系数为3.2×10~(-9)~13.0×10~(-9)cm~2/s,当扩散温度为1145℃时锂离子扩散系数约是1100℃时扩散系数的三倍。因此,适当提高扩散温度是提高气相输运平衡法制备近化学计量比低掺镁铌酸锂晶体效率的有效办法.     

Li2CO3掺杂对0.94Mg2SiO4-0.06Ca0.9Sr0.1TiO3陶瓷微波介电性能的影响

采用传统固相反应法,研究了Li2CO3掺杂对0.94Mg2SiO4-0.06Ca0.9Sr01TiO3微波介质陶瓷的烧结性能和介电性能的影响.结果表明,烧结助剂Li2 CO3的引入未改变陶瓷的相组成.添加适量的Li2CO3可以促进烧结,烧结温度由1440℃降低到1355℃,而且介电性能也得到了优化,Q ×f值有明显的提高;过量Li2CO3的引入,降低了材料的致密性,增加了陶瓷的介电损耗.在1355℃烧结,保温3h,添加0.50wt; Li2 CO3的0.94Mg2SiO4-0.06Ca09Sr0.1TiO3陶瓷获得最佳的介电性能:εr=7.96,Q×f=96409 GHz(f=14.571 GHz),τf=+4.62 ppm/℃.     

(C2N2H10)2Mg(HP2O7)2·2H2O synthesis and crystal structure

(C₂N₂H₁₀)₂Mg(HP₂O₇)₂·2H₂O, is a new inorganic organic hybrid structure. It has been synthetized using wet chemistry. Its crystal structure consists of cis- and trans-edge sharing [MgO₄(H₂O)₂] octahedra resulting in chains, which are linked via [HP₂O₇] units to form [Mg(HP₂O₇)₂(H₂O)₂]⁴⁻ layers. The Mg²⁺ cations and the ethylendiammonium cations are located on centers of inversion. The ethylendiammonium cations are alternately located in the interlayer space. The cohesion of the crystal is well ensured by coulombic interactions between anions and cations and by several hydrogen bonds. The diphosphate anion shows an eclipsed conformation.     

Crystal structure of Rb2[GeO2(OH)2]·2H2O

Single crystals of Rb₂[GeO₂(OH)₂] · 2H₂O are studied by X-ray diffraction. The crystals belong to the orthorhombic system, sp. gr. Pna2₁, a = 13.523(6) Å, b = 8.143(4) Å, c = 13.407(6) Å, Z = 8, R ₁ = 0.0506. In [GeO₂(OH)₂]^2? anions, the Ge-O distances (1.71–1.73(1) Å) are shorter than the Ge-OH distances (1.76–1.80(1) Å). Anions are linked to each other by pairs of hydrogen bonds to form infinite chains. The chains are linked by hydrogen bonds involving water molecules to form a 3D structure. The assignment of the bands in the IR spectrum of the compound under study is performed.     

Ultraviolet Absorption of Hg2Cl2-and Hg2Br2 Single Crystals

The optical unpolarized absorption spectra of Hg₂Cl₂ and Hg₂Br₂ single crystals were measured in the spectral range 230–400 nm. A sharp exciton peak and other absorption bands of both halides were observed near the fundamental absorption edge. The absorption peaks due to the splitting of the halogen doublet were also observed. Positions of the exciton peaks are characteristic for the Frenkel (localized) type of excitons. Possible interpretations of the other observed bands are discussed.     

Elastic properties of the dithionates Na2S2O6 · 2 H2O,K2S2O6, Rb2S2O6, CaS2O6 · 4H2O and SrS2O6 · 4 H2O

Single crystals of the title compounds having optical quality and dimensions of several cm were grown from aqueous solutions. The elastic and thermoelastic constants were determined from ultrasonic resonance frequencies of thick plates. The true point symmetry of K₂S₂O₆ and Rb₂S₂O₆, which is screened by a hexagonal hypermorphy, could be clearly revealed to be trigonal (32) by the existence of the elastic constant c₁₄. In the case of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O the constant c₁₄ of the specimens appeared too small to confirm the trigonal symmetry group required from electrooptic and non-linear optic effects unambiguously. The isotypy of K₂S₂O₂ and Rb₂S₂O₆ as well as that of CaS₂O₆ · 4H₂O and SrS₂O₆ · 4H₂O is confirmed by their elastic behaviour. The mean elastic stiffness of dithionates is closely related to that of the corresponding sulphates. In the vicinity of the second-order phase transition of K₂S₂O₆ near 235 K weak anomalies of the temperature derivatives of the longitudinal elastic stiffnesses are observed.     

Optical properties of the germanate melilites Sr2MgGe2O7, Sr2ZnGe2O7 and Ba2ZnGe2O7

Refractive indices and their dispersion in the wavelength range from 365 nm to 2325 nm and transmission ranges of the tetragonal melilite‐type germanates Sr₂MgGe₂O₇, Sr₂ZnGe₂O₇ and Ba₂ZnGe₂O₇ were determined. The uniaxial positive crystals Sr₂MgGe₂O₇ and Ba₂ZnGe₂O₇ both offer the possibility for phase matched second harmonic generation, a detailed analysis of phase matching conditions is given. The refractive indices of Sr₂ZnGe₂O₇ show an isoindex (isotropic) point at 467 nm. The investigation was performed on Czochralski grown large single crystals. The crystal structure of all three germanates were determined by means of X ‐ray diffraction. The results corroborate unmodulated melilite‐type structures at room temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure of bis 4-benzyl piperidinium monohydrogenmonophosphate pentahydrate, [C6H5CH2CHCH2CH2NH2CH2CH2]2HPO4·5H2O

The salt bis 4-benzyl piperidinium monohydrogenmonophosphate pentahydrate is orthorhombic with the following unit cell dimensions: a = 11.235(2) Å, b = 27.924(6) Å, c = 9.321(4) Å space group Pca2₁ with Z = 4. The structure was solved by the Patterson method and refined to final R value of 0.049 for 1802 independent reflections. The flack parameter is 0.14 with an e.s.d. of 0.23. The structure consists of infinite parallel two-dimensional [110] planes built of mutually connected ions and water molecules by strong O—H,...,O and N—H,...,O hydrogen bonding. There are no contacts other than normal van der Waals interactions between the layers.     

Identification of a new family of diphosphate compounds, AI2BII3(P2O7)2: Structures of Ag2Co3(P2O7)2, Ag2Mn3(P2O7)2, and Na2Cd3(P2O7)2

Syntheses and single-crystal X-ray structural results are reported for three new mixed diphosphates of the family A^I ₂B^II ₃(P₂O₇)₂; Ag₂Co₃(P₂O₇)₂ (I), Ag₂Mn₃(P₂O₇)₂ (II), and Na₂Cd₃(P₂O₇)₂ (III). All crystallize in the triclinic system, space group P1 bar: (I) a = 5.351(4), b = 6.375(4), c = 16.532(4) Å, = 80.83(6) = 81.45(4), = 72.87(5)°, V = 528.9(6) ų, Z = 2, D _calc = 4.649 mg/m³, R/Rw = 0.0428/0.0548 for 3949 obs. reflns; (II) a = 5.432(7), b = 6.619(6), c = 16.51(3) Å, = 80.78(8) = 82.43(9), = 72.82(7)°, V = 557.7(13) ų, Z = 2, D _calc = 4.338 mg/m³, R/Rw = 0.0679/0.1303 for 2100 obs. reflns and (III) a = 5.67(3), b = 7.08(4), c = 7.90(4) Å, = 77.0(2), = 82.5(2), = 67.8(2)°, V = 286(3) ų, Z = 2, D _calc = 4.249 mg/m³, R/Rw = 0.0307/0.0342 for 1945 obs. reflns. (I) and (II) are isostructural but (III) is of a different type. All three structures are characterized by layers of P₂O₇ groups alternating with layers of mixed metal atoms. Differences are seen in the conglomerate bonding patterns of B atoms and in the irregular geometry of Ag in (I) and (II) compared to the octahedral bonding seen for Na in (III). The differences in structure may be understood in terms of the ratios of the ionic radii of A and B atoms.     

Synthesis and characterization of (NH4)2CuBr2Cl2·2H2O crystals

Single crystals of a new compound, (NH₄)₂CuBr₂Cl₂.2H₂O, were grown from saturated aqueous solution at room temperature by slow evaporation method. The grown crystals were characterized through elemental, powder XRD, thermal and DSC analyses and FTIR and far IR spectra. The elemental analysis and the decomposition pattern formulated using the TG‐DTG studies confirm the stoichiometry of the compound. The crystallinity of the compound is confirmed from the powder XRD pattern. A preliminary single crystal X‐ray diffraction structural analysis reveals that the title compound belongs to the orthorhombic system with a = 7.7466 Å, b = 7.783 Å and c = 8.1211 Å. The low temperature DSC shows thermal anomalies at –161.1, –156.5, –152.4, –145.2, –134, –18.5, and 1.4°C during the heating run and at –4.3, –54.8, –66.1, –90.6, –109.7 and –147.2 °C during the cooling run. The thermal hysterses indicate first order phase transitions in the title compound at these temperatures. The FTIR spectra were used to assign the characteristic vibrational frequencies due to NH₄⁺, CuX₄^2– ions and other chemical bonds. The effect of substitution of two bromine atoms on the phase transitions of a closely related crystal, diammonium tetrachloro cuprate dihydrate is also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical Properties of MnIn2S2Se2 Single Crystals

Optical transmittance and reflectance spectra of MnIn₂S₂Se₂ single crystals are measured in the wavelength range from 0.5 to 30 μm. The interference method is used to determine the refractive index of the compound for wavelengths between 0.8 and 12 μm. From an analysis of the absorption spectrum it follows that the fundamental edge is due to forbidden indirect transitions between parabolic bands for the polarization E ⊥ c with a gap energy of 1.50 eV at room temperature.     

Oxygen-conducting compounds with La2Mo2O9 structure in the ternary system La2Mo2O9-Sm2W2O9-Sm2Mo2O 9 + : Synthesis and properties

Polycrystalline samples in the ternary system La₂Mo₂O₉-Sm₂W₂O₉-Sm₂Mo₂O ₉ ⁺ were synthesized in air. The region of the existence of compounds with the lanthanum molybdate (La₂Mo₂O₉) structure in this system was determined. The polymorphism of the synthesized compounds was studied. Doping with samarium or with samarium and tungsten was shown to lead to the suppression of the transition between the monoclinic and cubic phases α → β and the appearance of the transition β _ms → β between two cubic phases. In samples with a high samarium content, the phase transition β _ms → β manifests itself as significant anomalies in the temperature dependences of the dielectric permeability and electric conductivity. An increase in the concentration of samarium in the samples leads to a substantial decrease in the conductivity compared with the nondoped compound La₂Mo₂O₉.