Correlation between structure and photoluminescence of the europium doped glaserite-type phosphate Na2SrMg(PO4)2

X-ray diffraction, 31P NMR and europium photoluminescence properties of the Na2Ba1−xSrxMg(PO4)2 system related to the glaserite type structure

“…So, this contribution was related to the localization of the Eu 3+ in the Mg site. These observations are in agreement with those revealed in previous investigations on Na 2 SrMg(PO 4 ) 2 :Eu 3+ [10] and Na 2 BaMg(PO 4 ) 2 :Eu 3+ [11]. The second contribution related to the emission under 300 nm excitation is not so clear.…”

“…It may be caused by the large size of the barium site (hBa-Oi = 2.923 Å) which can easily accommodate Eu 2+ leading to natural reduction of Eu 3+ . The large band at high energy (below 250 nm) is similar to those observed in the two Eu 3+ doped compounds Na 2 MMg(PO 4 ) 2 with M = Sr, Ba [10,11]. It is related to the localization of Eu 3+ in a low crystal field site.…”

“…Sr 2+ . Therefore, we can conclude that all samples of the system Na 2 Ba 1Àx Sr x Mg(PO 4 ) 2 with compositions 0.6 6 x 6 1 crystallize, as Na 2 SrMg(PO 4 ) 2 , in the monoclinic symmetry with the space group P2 1 /a [10]. The decrease in symmetry is associated with transformation from trigonal to monoclinic system according to:…”

“…The initial model and the atomic coordinates are those obtained from the structural refinement of Na 2 SrMg(PO 4 ) 2 (x = 1) [10]. Crystal data are summarized in Table 1.…”

“…Based on a systematic investigation of the Na 3 PO 4 -Mg 3 (PO 4 ) 2 -M 3 (PO 4 ) 2 (M = Sr, Ba) systems, we recently identified two new phosphate compounds: Na 2 SrMg(PO 4 ) 2 [10] and Na 2 BaMg(PO 4 ) 2 [11] adopting the glaserite-type structure with different symmetries. Their structures are characterized by an anionic framework built up by the stacking, along the [0 0 1] direction, of two kinds of alternating [MgP 2 O 8 4À ] 1 layers parallel to the (a, b) plane and consisting of corner-sharing MgO 6 octahedra and PO 4 tetrahedra.…”