Study of electrical properties of La3+/Mn4+-modified PbTiO3 nanoceramics

The nanoscale samples of Pb_0.90La_0.10(Ti_1−x Mn _x )_0.975O₃ (x = 0.0, 0.04, 0.07, and 0.10) compounds were prepared using high-energy ball-milling method. Thermo-gravimetric analysis and high-resolution X-ray diffraction studies were carried out to verify the phase formation. Single-phase compounds were formed exhibiting tetragonal system. The presence of impedance and modulus spectroscopic data was used to gain an insight into the electrical properties of the samples and with a view to observing the relaxations in them. Impedance studies show non-freq-type behavior and the relaxation frequency shift toward higher frequency side with increase in temperature. An equivalent circuit has been used to provide a complete picture of the material. The difference between localized (i.e., dielectric relaxation) and non-localized conduction (i.e., long-range conductivity) processes within the bulk of the material may be discerned by the presence or the absence of a peak in the imaginary impedance and modulus versus frequency plot.     

LaMgAl11O19：Yb,Mn荧光粉中Yb^2＋与Mn^2＋的能量传递

利用共沉淀法制备了Yb和Mn离子共掺的LaMgAl11O19荧光粉。研究其室温下的发光性能。紫外光激发时观察到发光中心位于504nm的单一宽带发光峰,归因于Yb^2＋的激发态4f135d能级与基态4f14能级间的电子跃迁。同时观察到Yb和Mn共掺的LaMgAl11O19中存在Yb^2＋对Mn^2＋的传能现象,传能过程可...     

Mn2+掺杂多孔CdIn2S4光催化剂的制备及催化制氢性能

为提高光催化剂的比表面积,以十二烷基磺酸钠(SDS)为模板剂,采用水热法制备出系列Mn2+掺杂的CdIn2S4多孔光催化剂.通过XRD、FESEM、UV-Vis、XPS等分析手段对催化剂进行了表征,考察了掺杂Mn2+浓度对多孔CdIn2S4光催剂的形貌结构和可见光催化产氢性能的影响.结果表明,Mn2+掺杂影响催化剂的晶...     

The luminescence of Eu3+, Tb3+ and Tm3+ activated Gd2BaZnO5 and La2BaZnO5

The luminescence of several rare-earth activators in the new compounds Gd₂BaZnO₅ and La₂BaZnO₅ is reported and discussed. Activation with the Eu³⁺ ion yields highly efficient red-emitting phosphors. Some unknown structural details can be derived from the luminescence spectra.     

Luminescent properties of GdAl3(BO3)4:Ln3+ (Ln3+:Eu3+, Tb3+, Dy3+) nano-phosphors

GdAl₃(BO₃)₄:Ln³⁺ (Ln³⁺:Eu³⁺, Tb³⁺, Dy³⁺) nano-phosphors were prepared by sol–gel method. The structure properties of the phosphors are characterized by XRD, and GdAl₃(BO₃)₄:Ln³⁺ nano-phosphors have average sizes around 40 nm. The doping concentrations of Eu³⁺, Tb³⁺ and Dy³⁺ ions in GdAl₃(BO₃)₄ nano-phosphors are from 1 to 9 mol% for Eu³⁺ ions, from 2 to 12 mol% for Tb³⁺ ions and from 1 to 5 mol% for Dy³⁺ ions, respectively. The luminescent properties of rare-earth ions doped GdAl₃(BO₃)₄ nano-phosphors are analyzed by the photoluminescence spectra, which prime doping concentration of Eu³⁺, Tb³⁺, and Dy³⁺ ions are at 5, 12 and 3 mol%, respectively. The energy transfers in the luminescent processes of rare-earth ions doped GdAl₃(BO₃)₄ nano-phosphors are discussed.     

微波场作用下球形亚超细 CaS:Mn2+，Eu2+的快速合成

在微波场作用下,首次快速合成了球形亚超细尺寸的CaSMn     

Sm3+/Ce3+/Tb3+共掺CaO-B2O3-SiO2发光玻璃的制备及发光性能研究

采用高温熔融法制备了Sm3+/Ce3+/Tb3+共掺杂的CaO-B2O3-SiO2发光玻璃材料,并用荧光分光光度计和CIE色度坐标对其发光性能进行了研究。发射光谱表明,在374nm激发下,Sm3+/Ce3+/Tb3+共掺杂CaO-B2O3-SiO2发光玻璃的发射光谱中同时观测到了红橙光、蓝光和绿光的发射带,这些发射带的混合实现了白光发射。此外,在Sm2O3和Tb4O7含量不变的情况下,随着CeO2含量的减小,Sm3+/Ce3+/Tb3+共掺杂发光玻璃的发光颜色在白光区逐渐由蓝光区附近过渡到黄光区附近。     

Eu2+、Dy3+、Li+共掺杂CaSi2O2N2荧光粉的发光性能

采用高温固相反应法制备了一系列白光LED用CaSi2O2N2:0.05Eu2+,xDy3+,xLi+(0≤x≤0.03)荧光粉.利用X射线衍射仪对样品的物相结构进行了分析,结果表明:Dy3+和Li+离子的掺入没有改变CaSi2O2N2:Eu2+荧光粉的主晶相.利用荧光光谱仪对样品的发光性能进行了测试,发现所有样品的激发光谱均覆盖了从近紫外到蓝光的较宽范围,400 nm激发下得到的发射光谱为宽波段的单峰,峰值位于545 nm左右,是Eu2+离子5d-4f电子跃迁引起的.Dy3+离子掺杂可以提高CaSi2O2N2:Eu2+荧光粉的发光强度,Dy3+与Li+共掺杂可进一步提高荧光粉的发光强度,当Dy3+和Li+的掺杂量为1mol%时,荧光粉的发光强度达到最大值,是单掺杂Eu2+的荧光粉发光强度的157%.     

Influence of doping Nb5+ and Mn2+ on the PTCR effects of Ba0.92Ca0.05(Bi0.5Na0.5)0.03TiO3 ceramics

As a positive temperature coefficient of resistivity (PTCR) material, Ba_0.92Ca_0.05(Bi_0.5Na_0.5)_0.03TiO₃ ceramics with donor doping of Nb⁵⁺ and acceptor doping of Mn²⁺ were prepared by a conventional mixed oxide method. The influence of contents of Nb⁵⁺ and Mn²⁺ on the microstructure and PTCR characteristics of Ba_0.92Ca_0.05(Bi_0.5Na_0.5)_0.03TiO₃ ceramics sintered at 1,360°C for 2 h was investigated. The result showed that the Curie temperature (T _c) was shifted to a lower temperature with increasing of the content of Nb⁵⁺ and the resistance jump (ρ_max/ρ_min) was enhanced with doping of Mn²⁺. The grain size of ceramic sample decreased with increasing of contents of donor Nb⁵⁺ and acceptor Mn²⁺. The Ba_0.92Ca_0.05(Bi_0.5Na_0.5)_0.03TiO₃ ceramic with 0.4 mol%Nb⁵⁺ and 0.04 mol%Mn²⁺ exhibited a low ρ_RT of 5.0 × 102 Ω cm, a typical PTCR effect of ρ_max/ρ_min > 10³, and a T _c of 158°C.     

Luminescence properties for the high-pressure polymorphs of CaSiO3:Pb2+ and SrSiO3:Pb2+

High-pressure phases of CaSiO₃:Pb²⁺ and SrSiO₃:Pb²⁺ phosphors were synthesized at 40–55 kbar and 1000°C, $\text{viz}$. δ-CaSiO₃:Pb²⁺, δ-SrSiO₃:Pb²⁺, and δ′-SrSiO₃:Pb²⁺, and their luminescence properties were investigated. Among them, δ-CaSiO₃:Pb²⁺ was found to give a strong violet-blue emission ($\text{ca}$. 341 nm) as well as β-CaSiO₃:Pb²⁺ (an atmospheric phase), and the emission intensity of SrSiO₃:Pb²⁺ drastically increased when the host lattice transformed into high-pressure phases (δ and δ′ forms). These results were discussed by considering their structures and quenching temperatures of luminescences.     

Crystalline spectra of Pr3+ in CdF2

We report the first observation of line structure in the cathodoluminescence spectrum of cadmium fluoride crystals doped with trivalent praseodymium ions. CdF₂:Pr shows luminescence from ³P₁, ³P₀ and ¹D₂ to low lying levels of Pr³⁺ (³H, ³F). Anomalous temperature dependence of the emission decay measurements was observed. The decay-time constants decreased when the temperature was lowered within the range 300°–77°K. Possible mechanism for this phenomena is discussed.     

Luminescence and Optical-Memory model of SrAl2O4:Eu2+,Dy3+ and Sr4Al14O25:Eu2+,Dy3+

The photoluminescence, luminescence excitation, and phosphorescence spectra of SrAl²O⁴:Eu²⁺,Dy³⁺ and Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ powder phosphors have been studied in detail at 80 and 300 K. A conceptual model is proposed for strontium-aluminate-based optical memory.     

Yb3+、Er3+和Eu3+共掺杂TiO2纳米带的制备与表征

通过离子交换和水热两步合成过程简单制备了Yb3+、Er3+和Eu3+共掺杂锐钛矿型TiO2纳米带。该3种离子共掺杂未导致TiO2结构和形貌发生变化。光学特性测试结果表明,由于稀土离子掺杂浓度低,Eu3+掺杂未改变由Yb3+和Er3+产生的上转换发射峰位,但可观察到因上转换发光激发的Eu3+荧光发射峰;Eu3+荧光光谱也未受到Yb3+和Er3+掺杂的影响。通过对掺杂样品上转换发光机理的考察证实,上转换发光过程是双光子过程,但TiO2和Eu3+掺杂对此发光过程有明显影响。     

Sol-Gel法和微波法合成亚纳米级 Zn2SiO4:Mn2+ 高效绿色荧光体

采用     

Interactions of Cr2+ with the F− ligands in CdF2:Cr2+

Superhyperfine structure s.h.f.s. resulting from the Cr²⁺ - F^? interaction was studied in Cr²⁺ doped CdF₂ crystals. The s.h.f.s. observed can be described with by the following spin-Hamiltonian

$\text{H}\text{=}\text{g}{}_{\mathrm{eff}}\text{β}\text{HS}{}_{\mathrm{z}}\text{+ST}{}_{\mathrm{i}}\text{I+ST}{}_{\mathrm{j}}\text{I}$

The constants calculated are $\text{T}{}_{\mathrm{i\perp }}\text{≈}\text{T}{}_{\mathrm{i}}\text{= 50}\text{MHz}$$\text{T}{}_{\mathrm{j\perp }}\text{≈}\text{T}{}_{\mathrm{j}}\text{= 5}\text{MHz}$. The measurements were made with an ESR spectrometer at X band at 4.2 OK.     

CeO2∶Eu3+纳米晶的发光特性与Gd3+离子掺杂影响研究

以尿素为燃烧剂,采用低温燃烧法制备了Eu3+单掺杂和Eu3+、Gd3+共掺杂CeO2纳米晶粉末,用X射线衍射(XRD)和透射电镜(TEM)对样品进行了结构分析和形貌表征.对掺杂Gd3+离子的CeO2∶1％ Eu3+纳米晶的光谱研究发现,随着Gd3+离子掺杂浓度的增加,5D0→7F2跃迁与5D0→7F1跃迁的强度比随之增加,这表明Eu3++离子的格位对称性有所下降,且有利于提高红橙光的比例.鉴于CeO2基质在300～390nm有强吸收,Eu3+掺杂CeQ2纳米晶在近紫外激发LED荧光粉方面有潜在应用前景.     

Susceptibilite magnetique et R.P.E. du Mn2+ dans les verres du systeme : MnSGa2S3GeS2

E.P.R. and a.c. susceptibility measurements results are described. For low Mn²⁺ content well resolved E.P.R. signals are observed at g = 2 (hyperfine interaction constant : A = 71.10^?4cm^?1) and poorly resolved signals at g = 4.3. For high Mn²⁺ content the latter vanishes, and the temperature and concentration dependence of the g = 2 signal are indicative of magnetic exchange interactions. The a.c. susceptibility exhibits a cusp around 2 K (T_SG). The experiments can be interpreted by a progressive freezing of the magnetic moments, with a residual contribution of isolated Mn⁺⁺ below T_SG.     

Er3+/Yb3+掺杂NaGd(WO4)2粉体的制备与发光性能

采用水热法成功制备了Er~(3+)/Yb~(3+)双掺杂的NaGd(WO_4)_2纳米粉体,研究了不同络合剂、水热温度对样品形貌和结构的影响。测量了不同Er~(3+)掺杂浓度样品的可见上转换和近红外发射光谱。结果表明:在980nm LD激发下,可观测到样品强烈的绿色上转换发光,对应Er~(3+)的~2H_(11/2)→~4I_(15/2)(530nm)和~4S_(3/2)→~4I_(15/2)(552nm)跃迁,以及较弱的红色上转换和近红外发光,分别对应Er~(3+)的~4F_(9/2)→4I15/2(656nm)和~4I_(13/2)→~4I_(15/2)(1 532nm)跃迁。且随着Er~(3+)掺杂浓度的增加,样品的上转换红绿光和1.54μm附近的近红外光均呈现出先增大后减小的趋势。样品的激发和发射光谱显示,在378nm处的激发峰最强,对应Er~(3+)的~4I_(15/2)→~4 G_(11/2)能级跃迁,最强发射峰位于552nm。根据泵浦功率与发光强度的关系可以得出,红光和绿光的发射主要为双光子吸收过程,但红光还包含了一定的单光子吸收成分。