Reduction And Stability Of Trivalent Samarium Ions Doped In Barium Borophosphate

There have been many interests in research of Sm²⁺ doped materials since persistent spectral hole burning (PSHB) at room temperature (RT) was reported in Sm²⁺ doped inorganic material. Sm ions are stable in their trivalent state in many host materials. So it is necessary to reduce the Sm³⁺ ions to Sm²⁺ ions before the application of luminescence Sm²⁺ ions is explored.Usually, Sm²⁺ ions could be reduced by heating the material in reducing atmospheres. It was reported exposure to ioninzing radiations is another way to cause Sm³⁺ to Sm²⁺ conversion, such as X-ray irradiation or femto-second laser pulses. To compare the luminescece properties and stabilities of Sm²⁺ ions under two different reduction methods, we could find a better reducing process for PSHB material.In this work, BaBPO5 doped with the samarium ion was prepared by high temperature solid-state reaction. Sm²⁺ ions were obtained by two different reduction methods, i.e., heating in H2 redued atmosphere and X-ray irradiation. The luminescence spectra and decay curves from Sm²⁺ ions were detected in order to investigate reducing machanisms and stabilities of the two reducing methods.In the chapter three, the Sm²⁺ in BaBPO5 were obtained by heating in reducing atmospheres and the X-ray irradiation reduction method. It is found that the conversion of Sm³⁺→Sm²⁺ after X-ray irradiation was efficient. The Sm²⁺ under these two reduction methods exhibit different characteristics, which were studied by measurement of luminescence and decay.In the chapter four, the photostability of Sm²⁺ and defect structures of Sm²⁺ were discussed based on the thermo-luminescence and photo-bleaching experiments. The fluorescence intensity of Sm²⁺ doped in the two samples decreases upon excitation at 488 nm of Ar+ laser and this so-called photo-beaching effect. The luminescence properties and the photo-bleaching effects of the Sm²⁺ are highly dependent on the sample preparation conditions.In the chapter five, the reducing machanisms were discussed. The defects in BaBPO5 produced by the X-ray irradiation are different from those formed by heating the sample in H2 atmosphere. The latter defects are some native ones like (VB)"', (Vo)??? or (PB)???, while the former are much more complicated and unstable.Although Sm doped borophosphates have been paid great attention on recently, until now, X-ray irradiated Sm²⁺ doped BaBPO5 is not reported yet. This paper would do some contributions.