X-ray absorption and luminescence studies of Ba2Ca(BO3)2: Ce3+/Na+ phosphors

Abstract

X-ray excited optical luminescence (XEOL) spectroscopy has been used to investigate the optical emission properties of Ce(3+) activated Ba(2)Ca(BO(3))(2) with a charge-compensating Na(+) and the results are compared with the optical emission properties from UV excitation. Further, x-ray absorption near-edge structure (XANES) has been employed to study the chemical environment and energy transfer efficiency to optical emission upon x-ray excitation. XEOL results agree well with optical emission with UV excitation. XANES results across various absorption edges show that while the chemical environment of host materials does not change significantly with doping, luminescence yield decreases significantly at absorption edges due to an abrupt change in the de-excitation mechanism.

Synthesis Attempt and Structural Studies of Novel A2CeWO6 Double Perovskites (A2+ = Ba, Ca) in and outside of Ambient Conditions

“…Small features 1′ and 2′ (localized 3.4 eV apart, at the far beginning and end of each XAS band) are the same BaO/Ba–O–(Ce/W) related defects and impurities identified by XRD (Figure S5). − Their partial separation from the hot, post-synthesis matrix (due to WO 2 evaporation) could indicate unsuccessfully cerate formation via a BaO+CeO 2– x → BaCeO 3– x reaction.…”

“…They are from some unique defective Ca(+1)−O bonding being probably also distinctly related to the aforementioned Ba−O in BCW, but here, they are separated by a wider 4.3 eV gap. 125,126,129,130 Since those bands are much larger for XAS and are situated even closer to each other (being merely 1.5 eV apart) their interpretation is actually much more different. First, their contribution to the total signals stands around 27%.…”

Luminescence from TiO2 Nanotubes and Related Nanostructures Investigated Using Synchrotron X-Ray Absorption Near-Edge Structure and X-Ray Excited Optical Luminescence

“…Since the energy of core electrons is element specific, XANES allows to track the absorption behavior of an element to provide element-specific local environment, a combined XEOL-XANES technique will allow us to build the relationship between the observed luminescence and the type of element that is responsible for it, and predict the chemical environment that leads to such luminescence. This is particularly valuable when analysing the role of dopant or structural defect luminescence [35,36], as well as identifying the light-emitting component in a mixture of materials [24,32]. Figure 4 shows a schematic layout of a synchrotron radiation endstation for conducting such experiment.…”

Fingerprints of short-range and long-range structure in BaZr1−xHfxO3 solid solutions: an experimental and theoretical study

“…The XANES is able to determine the chemical surrounding (e.g., crystal field, density of unoccupied states, and the orientation of the specimen with respect to the polarization of the photon) 27,28 . Typically, measurements are made in transmission mode if attenuation length of the photon in the material being analysed is sufficiently long; however, in the soft X-ray region, due to small attenuation length, XANES measurements are made by detecting total electron yield (TEY), which is surface sensitive 29 . In the case of BZHO the absorptions of Zr K-edge and Hf L III -edge can be obtained by XANES/EXAFS transmission mode, while for Ba L III -edge and Zr L III /L II -edge the TEY methodology is more appropriated to operating condition of National Synchrotron Light Laboratory (LNLS).…”

“…27,28 Typically, measurements are made in transmission mode if attenuation length of the photon in the material being analysed is sufficiently long; however, in the soft X-ray region, due to small attenuation length, XANES measurements are made by detecting total electron yield (TEY), which is surface sensitive. 29 In the case of BZHO the absorptions of Zr K-edge and Hf L III -edge can be obtained by XANES/EXAFS transmission mode, while for Ba L III -edge and Zr L III /L II -edge the TEY methodology is more appropriated to operating conditions of the National Synchrotron Light Laboratory (LNLS). The X-ray absorption spectroscopy (XAS) has been applied in many case to investigate the local distortions of the BZO perovskite.…”