HCl气氛制备的ZnS:Mn粉末DCEL材料

本文首次较系统报导了HCl气氛中制备的ZnS:Mn粉末DCEL材料的特性。指出HCl气氛的主要作用,一是使材料结晶更好,二是引进Cl施主能级,使得PL和DCEL亮度提高。本实验还研究了ZnS粉在HCl气氛中灼烧时的相转换特点,以及晶相比对抗老化性能的影响。讨论了晶相比与颗粒表面CuxS导电相性质的关系,认为这是晶相比影响老化的原因。

ZnS:Mn DCEL PHOSPHORS PREPARED IN HCl ATMOSPHERE

The characteristics of ZnS:Mn powder phosphors fired in HC1 atmosphere are systematically described.This technology is with lower sintering temperature and shorter firing period because of the strong mineralization of HC1 gas. Thus, the phosphors obtained not only crystallize well, but also have smaller particle size. The brightness of the phosphors under UV and DC excitation is higher than that of phosphors produced in conventional way.In HC1 atmosphere, the recrystallization of the material is very rapid. The process can be finished in 10 min. The content ratio of hexagonal to cubic phase formed in sintering temperature is hardly shifted by slow cooling or annealing. This may be the effect of C1 induced by HC1 atmosphere. The experiment also suggests that ZnS raw material play an important role in forming crystalphase.In order to know the effect of different content ratio of crystalphase on DCEL, some ZnS:Mn samples with variable hexagonal phase composition were coated with copper and then aged under electric field. It is observed that the samples containing less hexagonal phase are better in maintenance. Thus, it may be concluded that the DCEL lifetime can be improved by appropriately reducing hexagonal phase content.In view of the symmetry of crystal field, hexagonal or cubic phase may affect the splitting of the activator’s energy level. Therefore, the brightness and the location of spectrum peak, but in spite of maintenance, can be influenced. So, the distinction of the lifetime should not be caused by different crystalphase. According to the model of Cu+ migration, it is considered that the problem of maintenance is associated with the property of CuxS phase. Hexagonal and cubic phase posses different crystal lattice, and their ratio determines the structure of CuxS which grows on those lattice. This has been identified from experimental data. The copper-coated ZnS raw material with cubic lattice shows high resistivity. And ZnS: Mn fired in lower temperature also has low conductivity because it contains more cubic phase composition on that preparing condition. However, the resistivity is usually lower for the material containing more hexagonal phase content. Generally, the maintenance characteristic is better for the sample with higher resistivity and is worse for that with lower one. So, the stability of CuxS phase is affected by the hexagonal phase content and that leads to different DCEL lifetime.This experiment suggests that the DCEL phosphors with higher brightness and longer lifetime are possible to be prepared by the sintering technology using HC1 atmosphere.