Luminescence properties of Sr3−x−3y/2MxCeyAlO4F (M=Ca,Ba, 0≤x≤0.9, 0.001≤y≤0.05) phosphors

Luminescent materials composed of Sr_3?x?3y/2M_xCe_yAlO₄F (M=Ca, Ba, 0≤x≤0.9, 0.001≤y≤0.05) were prepared by the solid-state reaction method. X-ray diffraction (XRD) patterns of the obtained oxyfluorides are exhibited for indexing peak positions. Dynamic excitation and emission spectra of the Ce³⁺-activated oxyfluoride phosphors are clearly monitored. The critical emission quenching as a function of Ce³⁺ contents in Sr_2.5?3y/2M_0.5Ce_yAlO₄F phosphors is revealed at quite low concentrations of the activator. CIE coordinates of blue and green Sr_2.5?3y/2M_0.5Ce_yAlO₄F phosphors are clearly measured. The relative quantum efficiency of Sr_2.4985Ca_0.5Ce_0.005AlO₄F based on the integrated emission is determined. The Sr_3?x?3y/2M_xCe_yAlO₄F phosphors excited near 410 nm light could be prominent phosphors in applications of NUV-LED.     

Pr1—xKxMnO3（0.0≤x≤0.15）的化学键性质研究

采用半经验的复杂晶体化学键理论研究了ｒ１－ｘＫｘＭｎＯ３的化学键性质。计算结果表明，Ｐｒ－Ｏ键及Ｋ－Ｏ的共价性随钾掺杂浓度的增加而略有减小，Ｍｎ－Ｏ的共价性则增加，且Ｍｎ－Ｏ的共价性要强于Ｐｒ（Ｋ）－Ｏ键，得到的键极化率也服从同样的规律。     

La0.67-xSmxSr0.33MnO3(0.40≤x≤0.60)体系的TCR研究

通过测量La0.67-xSmxSr0.33MnO3(x=0.40,0.50,0.60)体系的M～T曲线和ρ～T曲线,研究了La位Sm掺杂对体系电阻温度系数 (TCR)的影响.实验结果表明:Sm掺杂引起的电阻率曲线急剧变化,导致大的TCR出现;TCR在x=0.40时出现峰值,随Sm掺杂的增加,TCR值逐渐减小.体系出现大的TCR,来源于Sm掺杂引起的晶格畸变和额外磁性.     

Separation of magnetic phases in La1 − x CaxMnO3 manganites with 0.6 ≤ x ≤ 0.9

The magnetic properties of La_{1 ? x} Ca_xMnO₃ solid solutions were studied in wide temperature and magnetic field ranges, T = 2–600 K and H ≤ 50 kOe. Semiconducting compositions with 0.6 < × < 0.9 exhibited an unusual temperature behavior of magnetization and susceptibility with well-defined Curie and Néel temperatures. The simultaneous manifestation of both ferromagnetic and antiferromagnetic properties is evidence of the coexistence of two collinear magnetic phases. The content of impurity ions was shown to have a strong influence on the T _C and T _N values, whereas the ratio between the ferro-and antiferromagnetic phase volumes heavily depended on thermal treatment conditions. The magnetic properties of the whole series of La_{1 ? x} Ca_xMnO₃ solid solutions can be explained in terms of the phase separation model.     

Features of magnetic properties of La x MnO3 + δ (0.815 ≤ x ≤ 1.0)

Magnetic and resonance studies of the system of polycrystalline samples of self-doped manganites La _x MnO_{3 + δ} (x = 0.815, 0.90, 0.94, 0.97, and 1.0) have been performed in a temperature range of 77–300 K. According to ⁵⁵Mn NMR data, all samples contain a ferromagnetic phase at 77 K. As the defect density increases (x changes from 1.0 to 0.815), samples become more magnetically ordered. In this case, the ferromagnetic state of the system gradually changes from a mixed state in which both ferromagnetic insulating (basic) and ferromagnetic metal (for x = 0.97 and 1.0) phases coexist to only the ferromagnetic metal state (for x = 0.815 and 0.90). It has been shown that both ferromagnetic metal and ferromagnetic insulating phases are inhomogeneous, and either phase consists of two phases with different dynamics of nuclear spins and different Curie temperatures. The diagram of the magnetic phase state of the La _x MnO_{3 + δ} system (x = 0.815, 0.90, 0.94, 0.97, 1.0) has been constructed for a temperature range of 120–240 K and Mn⁴⁺ contents of 12–30%.     

La0.7Ca0.3Mn1-xCrxO3 (0.01≤x≤0.60)的低温热导

测量了锰位掺Cr系列巨磁阻多晶样品La0 .7Ca0 .3Mn1-xCrxO3(0 .0 1≤x≤ 0 .6 0 )的热导 ,实验温区 77～ 30 0K .随着Cr掺杂浓度x的增加 ,热导率κ(T)在所测温区内受到的压制变大 ,但当x =0 .6 0时 ,热导值却有较大的回升 ,显示了Cr掺入对晶格结构局部涨落的影响 .随温度降低 ,低掺杂样品在MI(金属 绝缘体 )转变点附近热导率κ(T)由dκ/dT >0变成dκ/dT<0 ,而高掺杂样品无MI转变 ,热导率随温度降低而减小 ,即dκ/dT >0 ,我们认为这是由载流子处于局域或巡游状态时与晶格的相互作用不同而导致的 .     

Nd0.3Sr0.7Mn1-xCrxO3(0.01≤x≤0.15)的低温热导率研究

报道Nd0.3Sr0.7Mn1-xCrxO3(0.01≤x≤0.15)的热导率在10~300K温区内随温度和Cr含量的变化关系.在所测温区,随着Cr掺杂的增加,样品热导率值整体上逐渐减小,但在x=0.15时,出现反弹.热导率值在绝缘体-金属转变附近有很大提高,这个提高随Cr含量的增加逐渐被压制,直到x=0.15消失.分析指出热导率在绝缘体-金属转变附近的提高是由声子热导率和自旋相关热导率两部分贡献的;Cr掺杂通过电荷、晶格和自旋相互作用影响和制约了热导率随温度的变化.结果表明体系中自旋对热导率的调制作用是不可忽略的.     

40≤Z≤44类镍离子3d94s,3d94p,3d94d组态s-p,p-d跃迁的计算

用多组态自洽场方法,结合我们提出的半经验拟合公式,对40≤Z≤44类镍离子3d94s,3d94p,3d94d态的能级进行计算,根据能级拟合值算出s-p,p-d跃迁的谱线波长,并给出各谱线的HFR振子强度.     

Preparation and Luminescent Properties of Sr3P2-xVxO8∶Eu (0≤x≤2.0)

研究了B位掺杂的Sr3P2-xVxO8(0≤x≤2.0)基质和Eu3+掺杂Sr3-3yEu2yP1.2V0.8O8(0＜y≤0.30)系列样品在紫外光激发下的发光性质.以两种不同紫外激发波长激发Sr3P2-xVxO8基质时,局部最大发光强度似乎与x值间存在周期性变化,且x=0.6和0.8时,Sr3P2-xVxO8样品具有最大发光强度.在Sr3P1.2V0.8O8基质中,Eu3+掺杂的最佳浓度为y=0.20.     

38≤Z≤42类钴离子n =3、Δn=0跃迁的理论计算

用多组态自洽场方法,结合作者提出的半经验拟合公式,首先对38≤Z≤42类钴离子3p63d9,3p53d10,3p63d84p组态的能级进行计算,然后根据能级值算出相应的电偶极跃迁的谱线波长,并给出各谱线的HFR振子强度。     

La0.67Ca0.33Mn1-xCrxO3(0.0≤x≤0.15)中异常的CMR效应

我们研究了Mn位掺Cr体系La0.67Ca0.33Mn1-xCrxO3（0．0≤x≤0．15）的磁怀和磁电阻性质,发现Cr掺杂对居里温度Tc影响不明显,但是导致了反常的电输运和磁电阻行为,随着Cr含量的增加,起始电阻率峰向低温移动,同时电阻率出现一个附加峰,在磁场作用下,两个电阻率峰被强烈压缩,导致CMR效应中出现双峰,并且CMR效应的温区被极大地拓宽,从低温直到接近室温,这个结果表明：Mn位元素替代是调节CMR效应的有效方法。     

Phase stratification in the Nd1 − x BaxCoO3 − δ (0.3 ≤ x ≤ 0.54) system

Slowly cooled Nd_{1 ? x} Ba_xCoO_{3 ? δ} samples were two-phase in the concentration interval 0.3 ≤ x ≤ 0.46. One of the phases had O-orthorhombic lattice distortions (Pbnm) characteristic of ferromagnetic samples with x ≤ 0.3, and the other phase had tetragonal distortions (P4/mmm) characteristic of samples with x ≥ 0.46. Tetragonal distortions were caused by ordering of Nd³⁺ and Ba²⁺ ions. Samples with ordered neodymium and barium ions (Nd_{1 ? y} Ba_{1 + y} Co₂O_{6 ? γ} at ?0.08 ≤ y ≤ 0.08) experienced metal-dielectric and orientation magnetic phase transitions.     

38≤Z≤42类钴离子n=3,△n=0跃迁的理论计算

用多组态自洽场方法,结合作提出的半经验拟合公式,首先对３８≤Ｚ≤４２类钴离子３ｐ＾６３ｄ＾９,３ｐ＾５３ｄ＾１０,３ｐ＾６３ｄ＾８４ｐ组态的能级进行计算,然后根据能级值算出相应的电偶极跃迁的谱线波长,并给出各谱线的ＨＦＲ振子强度。     

Level densities for nuclei with 47 ≤ A ≤ 59

Nuclear level densities of ⁴⁷V, ⁴⁸V, ⁴⁹V, ⁵³Mn, ⁵⁴Mn, ⁵⁷Co, ⁵⁹Ni and their energy dependences are determined from measurements of the neutron evaporation spectra in the (p, n) reaction. Neutron spectra from the (p, n) reaction on nuclei of ⁴⁷Ti, ⁴⁸Ti, ⁴⁹Ti, ⁵³Cr, ⁵⁴Cr, ⁵⁷Fe, and ⁵⁹Co are measured at proton energies between 7 and 11 MeV. The data are analyzed in terms of statistical equilibrium and pre-equilibrium models of nuclear reactions.     

Nd0．3Sro．7Mn1-xCrxO3（0．01≤x≤0．15）的低温热导率研究

报道Nd0．3Sro．7Mn1-xCrxO3（0．01≤x≤0．15）的热导率在10-300K温区内随温度和Cr含量的变化关系,在所测温区，随着Cr掺杂的增加，样品热导率值整体上逐渐减小，但在x=0．15时，出现反弹．热导率值在绝缘体-金属转变附近有很大提高，这个提高随Cr含量的增加逐渐被压制，直到x=0．15消失．分析指出热导率在绝缘体-金属转变附近的提高是由声子热导率和自旋相关热导率两部分贡献的；Cr掺杂通过电荷、晶格和自旋相互作用影响和制约了热导率随温度的变化,结果表明体系中自旋对热导率的调制作用是不可忽略的。     

La2/3(Ca1-xMgx)1/3MnO3(0≤x≤60%)系统中不寻常的超大磁电阻

用溶胶-凝胶法并经过1450℃后处理而制备出名义组分为La2/3(Ca1-xMgx)1/3MnO3 (0≤x≤60%)多晶样品.磁化测量表明,除磁转变温度因Mg掺杂而稍有降低外,磁性质整体上和不含Mg样品无本质上的差别.未加磁场下阻温关系测量表明,即使Mg含量高达60%,实验上仍观察到绝缘体到金属的转变.特别有意义的结果是,适当的Mg掺杂可明显提高转变温度附近的磁电阻效应,例如,在Mg掺杂量为30～40%的样品中,1T磁场下观察到的磁电阻甚至比不含Mg样品在5T磁场下得到的值还要大.     

Preparation and the physical properties of antiperovskite-type compounds Cd1-xInxNNi3 (0≤x≤0.2) and Cd1-yCuyNNi3 (0≤y≤0.2)

Two series of Cd1-xInx NNi3(0 ≤x≤ 0.2) and Cd1-yCuyNNi3(0≤y≤0.2) samples were prepared from CdO, In2O3 , CuO, and nickel powders under NH3 atmosphere at 773K. The structural and physical properties were investigated by means of X-ray powder diffraction temperature-dependent resistivity and magnetic measurements. X-ray powder diffraction results showed that the Cd 1 x In x NNi 3 and Cd 1 y Cuy NNi 3 compounds have a typical antiperovskite structure, and the CdNNi3, Cd0.9 In 0.1 NNi3 , and Cd0.9Cu0.1NNi3 compounds show metallic temperature-dependent resistivity and exhibit a Fermi liquid behavior at low temperature. In contrast to the paramagnetism previously reported, the CdNNi 3 sample exhibits very soft and weak ferromagnetism, and no superconductivity was found in the Cd 1 x In x NNi 3 and Cd 1 y Cu y NNi 3 samples down to 2 K. Each sample exhibited very soft and weak ferromagnetism, and the temperature dependence of the magnetization of the Cd 1-xInx NNi 3 and Cd1-y Cu y NNi 3 samples can be well fitted to the combination of a Bloch term and a Curie–Weiss term.