【摘要】 本工作研究了Sm³⁺离子在立方和六角两种结构硫化锌中的光谱。实验上,采用不同激发条件下的高分辨光谱、时间分辨光谱和激发光谱,同时配合低温退火处理实验,鉴别出硫化锌中Sm³⁺具有两种不同的发光中心。采用发光方法,第一次对稀土离子在硫化锌中的C_3v对称发光中心进行分析。在中间耦合自由离子能级基础上利用不可约张量方法和Wigner-Eckart定理进行晶体场计算,得到的晶体场参数实验值和点电荷模型计算的晶体场参数值相符合。更多还原

【Abstract】 Photoluminescence of single crystals and sintered slices of ZnS:Sm3 + was investigated. Sm3+ ions were introduced into samples by thermal diffusion. Three groups of lines, at 570nm,600nm and 650nm, were analyzed. They correspond to transitions of 4F5/ 2 -6H5/ 2, 4F5/2 - 6H7/2 and 4F5/2 -2H9/2, respectively.In the emission spectra of 4F5/2 - 6H5/2 transition of Sm3+ in ZnS(Fig.l) it was found that there were two groups of lines: lines 1,2 and 6 belonging to group It and lines 4 and 8 belonging to group I. The lines of group I keep the same relative intensities in different samples and the lines of group I also do so.From time resolved spectra it was found that the lines of the same groups had the same decay time.The lines of group I have decay time of 643us and group I has decay time of 475us (Fig.2). These two groups of lines also have different excitation spectra(Fig.3).The above experements prove that two groups of lines come from two different Luminescent centers, group I comes from center I and group II from center Ⅱ.In the emission spectra ( Fig.4 and 5 ) and the time-resolved spectra (Fig.6 and 7), lines G,H,J and X,Y are found to have the behavior similar to lines 4 and 85 lines K, L, M and N, O, P, Q are found to have the behavior similar to lines 1,2 and 6. By similar analyses lines G, H, J and X,Y are assigned to come from center I, lines K,L, M and N, O, P, Q are assigned to come from center II. Wavenumbers, relative intensities, decay times and splitting patterns of lines from center Ⅰ and Ⅱ are shown in Table 1.In order to identify the nature of the two centers crystal structure was analyzed. The single crystal samples have cubic structure with small amount of hexagonal structure and sintered slices have hexagonal structure mainly. From Fig.1 we know that the intensities of the lines of group Ⅰ are stronger in single crystals than in sintered slices and group Ⅱ is stronger in sintered slices than in single crystals. It seems that center Ⅰ is correlated with cubic structure while center I is correlated with the hexagonal one.Further support is given by the annealing experiments. After annealing at 450℃, the hexagonal structure in single crystals becomes undetectable and the intensities of group I become much weaker.Crystal field splittings were calculated by irreducible tensor method and using intermediate coupling wave functions of Sm3+ ion. The experimental crystal field parameters were deduced from experimental fitting. The crystal field parameters of different point charge models were also calculated. The calculated parameters have good agreement with the experimental parameters. It is important to consider inward relaxation of the nearest neighbour sulphur ions of Sm3+ ions in point charge model calculation.Center I consists of Sm3+ ions at zinc substitutional sites surrounded by the four nearest neighbour sulphur ions having cubic symmetry.The crystal field parameters areB04= -1222.4cm-1, BJ = 180.4cm-1.Center II has Sm3+ ions at zinc substitutional sites surrounded by the four nearest neighbour sulphur ions forming distorted tetrahedron having C3 symmetry.The crystal field parameters areB02= -237.6cm-1, B04 = 719.9cm-1, B24 = 872.0cm-1 , B06 = 328.4cm-1, B36= -187.9cm-1, B66= 200.0cm-1.更多还原