Low thermal expansion and broad band photoluminescence of Zr_(0.1)Al_(1.9)Mo_(2.9)V_(0.1)O_(12)

A new material of Zr0.1Al1.9Mo2.9V0.1O12 is synthesized by the traditional solid state synthesis method.The phase transition,coefficient of thermal expansion,and luminescence properties of Zr0.1Al1.9Mo2.9V0.1O12 are explored with Raman spectrometer,dilatometer,and x-ray diffraction(XRD)diffractometer.The results show that the Zr0.1Al1.9Mo2.9V0.1O12 possesses the strong broad-band luminescence characteristics almost in the whole visible region.The sample is crystallized in a monoclinic structure group of P21/a(No.14)crystallized at room temperature(RT).The crystal is changed from monoclinic to orthorhombic structure when the temperature increases to 463 K.The material has very low thermal expansion performance in a wide temperature range.Its excellent low thermal expansion and strong pale green light properties in a wide temperature range suggest its potential applications in light-emitting diode(LED)and other optoelectronic devices.     

Phase transition and thermal expansion property of Cr_(2-x)Zr_(0.5x)Mg_(0.5x)Mo_3O_(12) solid solution

Compounds with the formula Cr2-xZr0.5xMg0.5xMo3O12（x = 0.0, 0.3, 0.5, 0.9, 1.3, 1.5, 1.7, 1.9） are synthesized, and the effects of Zr4＋ and Mg2＋ co-incorporation on the phase transition, thermal expansion, and Raman mode are investigated. It is found that Cr2-xZr0.5xMg0.5xMo3O12 crystallize into monoclinic structures for x 〈 1.3 and orthorhombic structures for x _〉 1.5 at room temperature. The phase transition temperature from a monoclinic to an orthorhombic structure of Cr2Mo3O12 can be reduced by the partial substitution of （ZrMg）6＋ for Cr3＋. The overall linear thermal expansion coefficient decreases with the increase of the （ZrMg）6＋ content in an orthorhombic structure sample. The co-incorporation of Zr4＋ and Mg2＋ in the lattice results in the occurrence of new Raman modes and the hardening of the symmetric vibrational modes, which are attributed to the MoO4 tetrahedra sharing comers with ZrO6/MgO6 octahedra and to the strengthening of Mo-O bonds due to less electronegativities of Zr4＋ and Mg2＋ than Cr3＋, respectively.     

Phase transition and near-zero thermal expansion of Zr_(0.5)Hf_(0.5)VPO_7

The Zr_(0.5)Hf_(0.5)VPO_7 is successfully synthesized by the solid-state method with near-zero thermal expansion. Powder x-ray diffraction(XRD), Raman spectroscopy, thermal dilatometry, and scanning electron microscopy(SEM) are used to investigate the structure, the phase transition, and the coefficient of thermal expansion(CTE) of Zr_(0.5)Hf_(0.5)VPO_7. The investigation results show that the samples are of the single cubic type with a space group of Pa3ˉ at room temperature(RT).It can be inferred that the superstructure is transformed from the 3 × 3 × 3 superstructure to the 1 × 1 × 1 ideal crystal in a temperature range between 310 K and 323 K. The CTE is measured by a dilatometer to be 0.59 × 10~(-6) K~(-1)(310 K–673 K). The values of intrinsic(XRD) and extrinsic(dilatometric) thermal expansion are both near zero. The results show that Zr_(0.5)Hf_(0.5)VPO_7 has near-zero thermal expansion behavior over a wide temperature range.     

Tm0.1La0.9P5O14玻璃的上转换发光

本文报导了Tm_0.1La_0.9P₅O₁₄玻璃在红色的脉冲染料激光激发下产生的深蓝色和紫外上转换发光现象,对其上转换机理进行了简要的分析.     

Effects of Al particles and thin layer on thermal expansion and conductivity of Al-Y_2Mo_3O_(12) cermets

Low thermal expansion composites are difficult to obtain by using Al with larger positive thermal expansion coefficient(TEC) and the materials with smaller negative TECs. In this investigation, Y_2Mo_3O_(12) with larger negative TEC is used to combine with Al to obtain a low thermal expansion composite with high conductivity. The TEC of Al is reduced by 19%for a ratio Al:Y_2Mo_3O_(12) of 0.3118. When the mass ratio of Al:Y_2Mo_3O_(12) increases to 2.0000, the conductivity of the composite increases so much that a transformation from capacitance to pure resistance appears. The results suggest that Y_2Mo_3O_(12) plays a dominant role in the composite for low content of Al(presenting isolate particles), while the content of Al increases enough to contact each other, the composite presents mainly the property of Al. For the effect of high content Al, it is considered that Al is squeezed out of the cermets during the uniaxial pressure process to form a thin layer on the surface.     

Er0.1La0.9P5O14非晶的双光子上转换发光

本文研究了全浓度ＥｒＬａＰ５Ｏ１４非晶在波长λ为６４９．０ｎｍ脉冲染料激光激发下的上转换发光现象，并对其进行了简要的分析。     

Magnetic and thermal measurements on high-Tc (La0.9Ba0.1)2CuO4-y

We have measured the magnetic moment of (La_0.9Ba_0.1)₂CuO_4- as a function of temperature and magnetic field and have found the onset of superconductivity at a temperature T ⋍ 35 K. From the magnetic field dependencies, we have shown that the sample is a type-II superconductor with ≲ ⋍ 11. Specific heat measurements yield a finite electronic specific heat coefficient of ∼6 mJ/mole-K² at 4 K and a Debye temperature of only 330 K, suggesting that a strong electron-phonon interaction may be responsible for the high T in our sample.     

二维周期性多孔La_(0.83)Sr_(0.17)Mn_(0.9)Zn_(0.1)O_3发射率研究

基于麦克斯韦方程组,利用时域有限差分方法(FDTD)计算了二维周期性多孔钙钛矿型氧化物La_(0.83)Sr_(0.17)Mn_(0.9)Zn_(0.1)O_3(LSMZO)的光谱特性,讨论了结构尺寸对光谱特性的影响。计算结果表明,当孔径约比热辐射波长小一个量级时,周期性多孔LSMZO的发射率比块体材料有所提高,这对改善热致变色材料的性能具有一定的指导意义。     

钙钛矿氧化物异质结的研究进展

在过去几年中,为了研究钙钛矿氧化物异质结的物性和潜在的应用前景,我们进行了许多探索。在本文中,我们总结了对钙钛矿氧化物异质结一些物理性质的理论描述,揭示了La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3异质结中发现的正磁电阻效应和横向光电效应的物理起源。我们提出的理论模型将有助于理解界面对钙钛矿氧化物异质结各种性质的影响。     

Near-zero thermal expansion of In_(2(1-x))(HfMg)_xMo_3O_(12) with tailored phase transition

Solid solutions of In_(2(1-x)(HfMg)_xMo_3O_(12) are synthesized by solid state reaction with the aim to reduce the phase transition temperature of In_2Mo_3O_(12) and improve its thermal expansion property.The effects of(HfMg)~(6+) incorporation on the phase transition and thermal expansion are investigated.It is shown that the monoclinic-to-orthorhombic phase transition temperature obviously decreases and the coefficient of thermal expansion(CTE) of the orthorhombic becomes less negative and approaches to zero with increasing the content of(HfMg)~(6+).A near zero thermal expansion covering the case at room temperature(RT) is achieved for the solid solutions with x ≥ 0.85,implying potential applications of this material in many fields.     

Y3Al5O12的热输运性质的第一性原理研究

基于密度泛函微扰理论（DFPT）结合模守恒赝势方法进行晶格动力学模拟.得到了钇铝石榴石（YAG）的声子态密度、分波声子态密度和声子的色散谱.利用第一Brillouin区的特殊点取样方法,计算了YAG的比热容和布局数平均的声子群速度.在非谐相互作用下,利用Fermi黄金公式结合第一Brillouin区的特殊点取样方法,得出了YAG非谐声子平均自由程.综合考虑了两种声子散射机制,得到了YAG陶瓷的热导率.结果表明,对于YAG陶瓷,在低温时,晶界散射将对热阻起主要作用;在高于一定温度时,三声子相互作用对热阻的贡献将占主导地位.同时也从理论上证明了Sato等提出的在室温以上,YAG陶瓷与单晶的热导率的差异可以忽略的观点.所得到的热导率、比热容随温度的变化与实验结果很好地符合. 关键词： 声子平均自由程 密度泛函微扰理论 3Al₅O₁₂声子结构')" href="#">Y₃Al₅O₁₂声子结构 热导率     

Optical spectra of (CdF2)0.9(InF3)0.1 semiconductor solid solutions

The differences in the optical spectra of CdF₂:In semiconductors with bistable DX centers (concentrated (CdF₂)_0.9(InF₃)_0.1 solid solutions) and “standard” samples with a lower impurity concentration used to record holograms are discussed. In contrast to the standard samples, in which complete decay of two-electron DX states and transfer of electrons to shallow donor levels may occur at low temperatures, long-term irradiation of a (CdF₂)_0.9(InF₃)_0.1 solid solution by UV or visible light leads to decay of no more than 20% deep centers. The experimental data and estimates of the statistical distribution of electrons over energy levels in this crystal give the total electron concentration, neutral donor concentration, and concentration of deep two-electron centers to be ～5 × 10¹⁸ cm^?3, ～9 × 10¹⁷ cm^?3, and more than 1 × 10²⁰ cm^?3, respectively. These estimates show that the majority of impurity ions are located in clusters and can form only deep two-electron states in CdF₂ crystals with a high indium content. In this case, In³⁺ ions in a limited concentration (In³⁺ (～9 × 10¹⁷ cm^?3) are statistically distributed in the “unperturbed” CdF₂ lattice and, as in low-concentrated samples, form DX centers, which possess both shallow hydrogen-like and deep two-electron states.     

Laser scattering,transmittance and low thermal expansion behaviors in Y_(2-x)(ZnLi)_xMo_3O_(12) by forming regular grains

Ceramics usually have irregular grains, cracking, or porosity, which result in their lightproof.Y_2Mo_3O_(12) ceramics have more porosity due to the heavy hygroscopicity.Introducing ZnLi to Y_2Mo_3O_(12) could form regular grains, reduce cracking and porosity.With increasing the content of ZnLi, the grain shapes self-assembly gradually and then the laser scattering and transmittance improve.The laser scattering property and transmittance of diverging rays become the best in ceramics Y_(2-x)(ZnLi)_xMo_3O_(12)(x = 1.0 and 1.2) with regular grains and low thermal expansion.The formation mechanism of regular grains is ascribed to the substitutions of Zn~(2+)and Li+for Y~(3+) in Y_2Mo_3O_(12) resulting in the preferential growth.The investigation in laser scattering, transmittance and low thermal expansion behaviors of Y_(2-x)(ZnLi)_xMo_3O_(12) could pave a way to weaken the strong-laser attack from the high-power laser weapon and the other.     

Optimization of Pr(0.9)Ca(0.1)MnO(3) thin films and observation of coexisting spin-glass and ferromagnetic phases at low temperature

Optimization of thin films of small bandwidth manganite, Pr(1-x)Ca(x)MnO3 (for x = 0.1), and their magnetic properties are investigated. Using different pulsed laser deposition (PLD) conditions, several films were deposited from the stoichiometric target material on SrTiO3 (001) substrate and their thorough structural and magnetic characterizations were carried out using x-ray diffraction, atomic force microscopy, x-ray photoelectron spectroscopy (XPS), SQUID magnetometry and ac susceptibility measurements. A systematic investigation shows that irrespective of the growth temperature (between 550 and 750?°C), all the as-deposited films have twin boundaries and magnetic double phases. Post-annealing in partial or full oxygen pressure removes the extra phase and the twin boundaries. Zero-field-cooled magnetization data show an antiferromagnetic to paramagnetic transition at around 100 K whereas the field-cooled magnetization data exhibit a paramagnetic to ferromagnetic transition close to 120 K. However, depending on the oxygen treatments, the saturation magnetization and Curie temperature of the films change significantly. Redistribution of oxygen vacancies due to annealing treatments leading to a change in ratio of Mn3+ and Mn4+ in the films is observed from XPS measurements. Low temperature (below 100 K) dc magnetization of these films shows metamagnetic transition, high coercivity and irreversibility magnetizations, indicating the presence of a spin-glass phase at low temperature. The frequency dependent shift in spin-glass freezing temperature from ac susceptibility measurement confirms the coexistence of spin-glass and ferromagnetic phases in these samples at low temperature.     

XRD,XPS, SEM/EDX and broadband impedance spectroscopy study of pyrophosphate (LiFeP2O7 and Li0.9Fe0.9Ti0.1P2O7) ceramics

LiFeP₂O₇ and Li_0.9Fe_0.9Ti_0.1P₂O₇ were synthesised by solid-state reaction and ceramics were sintered. The structure of compounds was studied in the temperature range 300–700 K by X-ray diffraction. Ceramics’ surfaces were investigated by scanning electron microscope. Binding energies of Fe 2p, P 2p and O 1s core levels at ceramics’ surfaces have been determined by X-ray photoelectron spectroscopy and different valence states of Fe and P were detected. Elemental compositions of the compounds were studied by energy dispersive X-ray spectrometer. Impedance spectroscopy was performed in the frequency range 10 Hz–3 GHz and in the temperature interval 400–700 K. The changes of the activation energy of ionic conductivity at 528 and 550 K for LiFeP₂O₇ and Li_0.9Fe_0.9Ti_0.1P₂O₇, respectively, were found. The phenomena can be related to disordering in the unit cells of the compounds.     

Magnetic,dielectric, and transport properties of bismuth pyrostannate Bi2(Sn0.9Mn0.1)2O7

Physics of the Solid State - The effect of replacing manganese ions on the structural, dielectric, transport, and magnetic properties of Bi2(Sn0.9Mn0.1)2O7 has been studied and the correlation...     

Improvement of Cyclic Stability of Na_(0.67)Mn_(0.8)Ni_(0.1)Co_(0.1)O_2 via Suppressing Lattice Variation

Strategies to prolong operational life are highly pursued to strengthen the advantage of cost-effectiveness on sodium-ion batteries(SIBs).We demonstrate the crucial influence of particles' internal mechanical strains on durability of cathode,which does not attract enough attentions from the community.Among the investigated samples,2% Ti-modified-Na_(0.67)Ni0_(.1)Co_(0.1)Mn_(0.8)O_2 suppresses the c-axis lattice variation b_y 38%,attains the reversible capacity 86% higher after 200 cycles,and still keeps intact morphology.This approach indicates that the mechanical properties could tailor cyclic stability of cathode,which is particular important to further improve competitiveness for SIBs.     

Dielectric and piezoelectric properties of(110) oriented Pb(Zr_(1-x)Ti_x)O_3 thin films

A phenomenological Landau–Devonshire theory is developed to investigate the ferroelectric, dielectric, and piezoelectric properties of(110) oriented Pb(Zr_(1-x)Ti_x)O_3(x = 0.4, 0.5, 0.6, and 0.7) thin films. At room temperature, the tetragonal a_1 phase, the orthorhombic a_2c phase, the triclinic γ_1 phase, and the triclinic γ_2 phase are stable. The appearance of the negative polarization component P_2 in the a_2c phase and the γ_1 phase is attributed to the nonlinear coupling terms in the thermodynamic potential. The γ phase of the Pb(Zr_(1-x)Ti_x)O_3 thin films has better dielectric and piezoelectric properties than the a_2c phase and the a_1 phase. The largest dielectric and piezoelectric coefficients are obtained in the Pb(Zr_(0.5)Ti_(0.5))O_3 thin film. The piezoelectric coefficient of 110–150 pm/V is obtained in the(110) oriented Pb(Zr_(0.5)Ti_(0.5))O_3 thin film, and the Pb(Zr_(0.3)Ti_(0.7))O_3 thin film has the remnant polarization and relative dielectric constant of 50 μC/cm~2 and 100, respectively,which are in agreement with the experimental measurements reported in the literature.     

Superconductivity of Bi2 (Sr0.9Ca0.1)2 CuO y single crystals

Bi₂ (Sr_0.9Ca_0.1)₂ CuO _y single crystals were grown by the self-flux method. The temperature dependence of resistance and ac susceptibility measurements showed that the as-grown crystal is semiconductive between 4.2 K and 300 K. However, after annealing in air for more than 20 days the crystal became superconducting with a T _c of 66 K obtained from the R-T curve. The ac susceptibility data also showed a strong superconducting transition at 71 K. X-ray diffraction indicated that the structure of the as-grown and the annealed crystal both are orthorhombic. The T _c of 71 K of the Bi₂ (Sr_0.9Ca_0.1)₂ CuO _y crystal may be due to the increase of oxygen content in the crystal after the long-time annealing in air. It is suggested that the superconductivity of the Ca-doped 2201 phase of the Bi-based system, which up to now was found to have a T _c=7–22 K, is similar to the 2201 phase of the Tl-based system.     

准分子激光蒸发YBa_2Cu_3C(7-x)靶产生等离子体的膨胀过程研究

对XeCl准分子激光蒸发YBa_2Cu_3O_(7-x)陶瓷靶产生的等离子体进行了实验和理论研究.利用发射光谱,分辨出等离子体内的各种粒子.并对各种粒子进行了飞行时间谱测量.在实验的基础上,建立了一个等离子体的膨胀模型.计算结果与实验符合较好.