摘要
本文研究了化学计量的基质发光材料Na_5Eu(MoO_4)_4和NaEu(MoO_4)_2.它们都属于四方晶系,空间群为I4_(1/α ).NaEu(Mo0_4)_2属于白钨矿(scheelite)结构,一个晶胞中有2个分子式NaEu(MoO_4)_2(z=2);而Na_5Eu(Mo_4O)_4属于类自钨矿(scheelite-like)结构,一个晶胞中有4个分子式Na_5Eu(MoO_4)_4(z=4).X射线衍射确定的晶胞常数,对Na_5Eu(MoO_4)_4,α=1.1439nm和c=1.1486nm(密度d计算=4.01g/cm^3,z=4);对NaEu(MoO_4)_2,α=0.5236nm和c=1.1439nm(密度d_(计算)=5.24g/cm^3,z=2).由差热法和X射线衍射法确定了Na_2MoO_4-Eu_2(MoO_4)_3的相图.Na_5Eu(MoO_4)_4分解为NaEu(MoO_4)_2的温度是700℃.本文确定了制备纯 Na_5Eu(MoO_4)和NaEu(MoO_4)_2的方法,并研究了上述两种材料的激发光谱和发光光谱.确定了用X射线粉末衍射谱和发光光谱鉴别Na_5Eu(MoO_4)_4和NaEu(MoO_4)_2的方法.在365nm紫外光激发下,Na_5Eu(MoO_4)_4的发光比Na_5Eu(WO_4)_4的强得多,在室温下,Na_5Eu(MoO_4)_4,NaEu(MoO_4)_2和Na_5Eu(WO_4)_4的相对发光积分亮度比为3.8:3.2:1.0.
Na5Eu(MoO4)4 like Na6Eu(WO4)4 is a kind of good stoichiometric host luminescent material having high concentration of Eu3+ and no concentration quenching effect.The power crystals Na5Eu(MoO4)4 and NaEu(MoO4)2 have been synthesized. According to differential thermal and X-ray diffraction analyses, a phase diagram of the system Na2MoO4-Eu2(MoO4)3 has been determined.The methods for synthesizing pure Na5Eu(MoO4)4 and NaEu(MoO4)2 have been determined. It shows that Na5Eu(MoO4)4 will not be dissociated to NaEu(MoO4)2 when Na2MoO4 is excessive and the ratio of molal concentration of Na2MoO4 to Eu2O3 is more than about 8 : 1 at sintering temperature lower than 700℃.Both of Na5Eu(MoO4)4 and NaEu(MoO4)2 crystallize in the schee-lite structure type and belong to the tetragonal crystal system. The X--ray powder diffraction pattern of NaEu(MoO4)2 was indexed in a'pure' scheelite cell with parameters α = 0.5236nm and c = 1.1439nm (dcalc = 5.24g/cm3, z=2, space group I4,/α). Thus, the entire series of NaEu (MoO4)2 compounds is isostructural. But all of the X-ray powder diffraction lines of Na5Eu(MoO4)4 can only be indexed in the enlarged scheelite cell with parameters α = 1.1439nm and c = 1.1486nm (dcaic= 4.01g/cm3, z=4, space group I41/α). In this paper, the cation distribution in the unit cell of both compounds is discussed.The purity of Na5Eu(MoO4)4 and NaEu(MoO4)2 samples can be determined sensitively by the intensity analysis of main peaks of the two compounds by X-ray diffraction mathod.The excitation and emission spectra of both compounds have been determined. The emission lines belong to 5D0 to 7Fi transitions of Eu 3+ and the main emission peaks of 6D0 to 7F2(E) and 7F2(B) are 617.4 and 613. 1nm for Na5Eu(MoO4)4, and 615.6 and 612.7nm for NaEu (MoO4)2, respectively. According to this, the purity of the two compounds can also be determined by luminescent spectrum method. The emissions of 5D2 to 7Fi and 5D1 to 7Fi of Eu3+ are not observed at room temperature. The reason might be that a strong double or triple phon
出处
《发光学报》
EI
CAS
CSCD
北大核心
1991年第2期118-126,共9页
Chinese Journal of Luminescence
