LUMINESCENCE OF BI(3+) AND THE ENERGY-TRANSFER FROM BI(3+) TO R(3+) (R=EU,DY,SM,TB) IN ALKALINE-EARTH BORATES

At room temperature, the Bi3+ ion shows broad band characters of its luminescence in Ca2B2O5, M3B2O6 ( M=Ca,Sr ) and SrB4O7. The maxima of the Bi3+ S-1(0)-->P-3(1) absorption bands are located in the range of 240-300nm, but the energy variation of the corresponding P-3(1)-->S-1(0) emissions is very large. The maxima of these emission bands change from 350nm in Ca3B2O6;Bi3+ to 586nm in SrB4O7:Bi3+. The Stokes shift of the Bi3+ luminescence increases from 6118 cm-1, in Ca2B2O5:Bi3+, to 24439 cm-1, in SrB4O7:Bi3+. The emission intensity of the Bi3+ luminescence increases with the decreasing Stokes shift. It has been found that in Ca2B2O5, the Bi3+ ion could transfer its excitation energy to the R3+ ions ( R=Eu, Dy, Sm, Tb ) , but in, Ca3B2O6 and Sr3B2O6, only Bi3+-->Eu3+ was observed. No energy transfer from Bi3+ to R3+ was detected in SrB4O7.

YV_(1-x)B_xO_(4-x):Eu~(3+)(或Dy~(3+),Bi~(3+))的合成及光谱性质的研究

本文报道了Eu~(3+)、D~(3+)在YV_(1-x)B_xO_(4-x)中的光谱性质。实验表明:B~(3+)取代V~(5+)时,可使基质和Dy~(3+)的发射强度及黄兰比下降,并使基质的吸收带短移。而B~(3+)取代Y~(3+)时,则可提高Dy~(3+)的黄兰比。同时我们还研究了Bi~(3+)和温度对YV_(0.69)B_(0.31)O_(3.69):Dy~(3+)中Dy~(3+)发射强度的影响。

掺W对Bi系中高Tc超导相的影响

自Maeda发现高Tc超导体BiSrCaCuO以来,引起了人们广泛兴趣;由于它有较高的超导转变温度(Tc>100K),无剧毒、价廉和自高温冷却到室温无结构相变等特点,Bi系是一很有实用前景的高Tc超导体;已经确定Bi系中含有三个超导相(2201,2212,2223相),但是迄今要制得较纯的2223高Tc相还有一定困难,无疑这对它的基础研究和实用开发都受到了限制,因此制备更纯的Bi系2223相具有重要的意义。

V、Nb、Ta对促进Bi系超导体中2223相生成作用研究

自发现BiSrCaCuO超导体以来,为了稳定2223高T_C相结构、增加其在超导体中的含量,在该体系中引入掺杂元素Pb被公认是最有效的方法。我们系统研究了V~(5+)、Nb~(5+)、Ta~(5+)高价离子的单独掺入Bi系中对

Bi系中2212相的超导电性研究

已知在Bi系高Tc超导体中存在三个超导相:2223相的Tc～110k,c～37(?);2212相的Tc～85k,c～30.6(?);2201相的Tc～10k。在实验过程中,我们注意到还可能有另外的超导相存在,通过改变元素名义配比和制备工艺观察到一个具有2212相结构,但Tc却表现为～105k的新现象存在。 实验部分 样品制备采用固相反应方法将Bi_2O_3、PbO、Sb_2O_3、SrCO_3、CaCO_3、CuO(均为A.R.级)混匀、碾磨,于～810℃在刚玉坩埚中预烧20h;再碾,压片后于～870℃在磁舟中烧结60-240h,然后作测试分析。

Nb(Ba)加强Bi系中2223相生成作用研究

固相法合成系列名义组成为Bi_(2-x)Nb_xSr_2Ca_2Cu_3Oy(x=0—1.0)的样品,电学和磁学测量表明,当掺入x=0.2—0.3的Nb有明显加强2223相生成的作用,配比为Bi_(1.7)Nb_(0.3)Sr_2Ca_2Cu_3Oy时最佳;当掺Ba以部分取代Sr后有明显协同Nb促进22 23相生成的作用,比单掺Nb效果更为显著,其中以Bi_(1.7)Nb_(0.3)Sr_(1.8)Ba_(0.2)Ca_2Cu_3Oy为最优组成。热重分析(TGA)实验显示,掺Nb(Ba)后样品在～600°C出现吸氧增重;XPS中的O_(1s)峰显示掺Nb(Ba)后除～531eV的主峰外,在～529eV的肩峰更加明显;讨论了Nb(Ba)对晶体结构的可能影响。

Ba_2RV_3O_(11)(R=Y,Gd,La):Eu~(3+)(或Dy~(3+),Bi~(3+))的合成及发光性能的研究

本文报导了Eu~(3+),Dy~(3+)在Ba_2RV_3O_(11)(R=Y,Gd,La)基质中的光谱性质、Bi~(3+)对Dy~(3+)发射强度的影响及温度对Dy~(3+)发射强度的猝灭情况.研究了被取代离子R~(3+)(R=Y,Gd,La)对基质电行迁移带、Eu~(3+)的红橙比、Dy~(3+)黄蓝比的影响,还给出了Dy~(3+)的浓度猝灭值.

THE CATALYTIC BEHAVIOR AND REACTION-MECHANISM OF THE BI-CE-O SYSTEM CATALYSTS IN THE OXIDATIVE DEHYDROAROMATIZATION OF PROPYLENE

Oxidative dehydroaromatization of propylene was investigated by the pulse technique over two kinds of single oxide catalysts. With the Bi2O3 catalyst, the main dimer product was 1,5-hexadiene, and the dimerization activity was stable to pulse number even if the catalyst was partly reduced to the bulk. With the CeO2 catalyst, benzene was mainly formed instead of 1,5-hexadiene, but the activity decreased rapidly with increasing pulse number, indicating that only the lattice oxygen near the catalyst surface could be used for oxidative dimerization and the further aromatization. The Bi-Ce-O system catalyst was found in this study to give higher aromatization activity and showed better stability, compared to the Bi-Sn-O catalyst. Although the Bi-Ce-O catalyst was only a mixture of the two component oxides from X-ray diffraction analysis, there was a significant combination effect on the selectivity to benzene. The highest and the most stable selectivity of benzene was obtained at Bi/Ce = 1. In the TPD spectrum of Bi-Ce-O catalyst, there are not only the lattice oxygen (beta-oxygen) over 620-degrees-C due to the reduction of Bi2O3, but also a great deal of the alpha-oxygen desorbed about 400-degrees-C, which is considered the absorbed oxygen in the bulk. This absorbed oxygen could probably be a compensation of the lattice oxygen through the route of gaseous --> absorbed --> lattice oxygen in the binary catalyst system. By the kinetic study on the Bi-Ce-O catalyst, the dimer formation rate was the first-order with respect to the partial pressure of propylene and zero-order of oxygen. Although detail investigation would be made further, it was considered that the complete oxidation of propylene would mainly take place parallelly on some different sites, and the rate-determining step of propylene dimerization occurred probably between an adosrbed propylene and a gaseous one by an Eley-Rideal type mechanism.

硼酸盐玻璃中Gd~(3+)、Dy~(3+)、Bi~(3+)对Tb~(3+)发光性质的影响

本文研究了单掺和双掺(Tb~(3+)、Tb~(3+)+Gd~(3+)、Tb~(3+)+Dy~(3+)、Tb~(3+)+Bi~(3+)约四十余种不同成份的硼酸盐玻璃。探讨了玻璃成份对Tb~(3+)发光性质的影响和Gd~(3+)、Dy~(3+)、Bj~(3+)对Tb~(3+)的胜化作用。在B_2O_2-BaO-M_mO_n(M_mO_n=Li_2O、Na_2O、K_2O、MgO、CaO、SrO、Al_2O_3、La_2O_3和Bi_2O_3)玻璃体系中,当M_mO_n分别为MgO和Al_2O_3时,Tb~(3+)的发光强度最强;M_mO-n为Bi_2O_3时,Tb~(3+)的发光强度最弱。Tb~(3+)的特征发射峰分别随着碱金属、碱土金属和三价金属的离子半径增加而红移。Gd~(3+)、Dy~(3+)、Bi~(3+)对Tb~(3+)均有敏化作用。特别是Gd~(3+),使Tb~(3+)的发光强度增加1～3.8倍,其最佳敏化浓度,因基质玻璃成份而异。

Sm~(3+)在硼酸盐玻璃中的发光及Bi~(3+)对Sm~(3+)的敏化作用

早在六十年代,人们为了寻找较好的激光玻璃,曾对Sm~(3+)离子掺杂的玻璃中的光谱进行过研究。为了探寻新型的激光,发光玻璃,又进一步研究了Sm~(3+)在玻璃中的发光和敏化。我们以寻找一种高亮度,低成本的发光玻璃为目的,研究了基质玻璃组成,敏化离子及其浓度对Sm~(3+)发光性质的影响。 选择B_2O_3-BaO-M_mO_n(M_mO_n=Li_2O,Na_2O,K_2O,MgO,CaO,SrO)玻璃体系,所用原料的纯度皆为分析纯以上,用陶瓷坩埚在1250℃掺杂氧化钐(纯度均大于99％),玻璃的荧光谱和激发光谱,用MPF-4型荧光分光光度计测定。

Bi系高温超导体中2212相和2223相的性质分析

本文对 Bi 系中可能存在一种 T_c>100K 的2212相作了进一步的论证.化学分析显示普通的2212相中 Cu~(3+)含量为～10%,而2223相和 T_c>100K 的2212相中 Cu~(3+)的含量却大于30%.从 DTA-TG 实验中观察到普通2212相和2223相失去晶格氧的量为0.8%,而含 T_c>100K 的2212相的样品失去晶格氧的量为～2%,说明这种2212相受氧含量影响更大.文中还介绍了一种简易判断样品中是否存在2223相和普通2212相的经验方法.

高Jc Ag-Bi-Pb-Sr-Ca-Cu-O超导材料

Bi_2Sr_2Ca_2Cu_3O_y-Ag_x、Bi_(1.7)Pb_(0.3)Sr_2Ca_2Cu_3O_y-Ag_x和Bi_(1.7)Pb_(0.3)Sr_2Ca_2Cu_(3.2)O_y-Ag_x系列的超导材料是用固相反应的方法合成的。原料为分析纯AgNO_3、PbO、Bi_2O_3、CaCO_3、SrCO~3和CuO。把试剂按所需配比混和研磨后,在800℃烧12h,研磨压片,片子在850℃烧结200h,破碎、研磨后,按配比加入AgNO_3·800℃灼烧12h,再次研磨、压片,850℃再烧结200h,炉冷至室温。