Malika Trabelsi-Ayedi

Relationships between structural and luminescence properties in Eu3+-doped new calcium borohydroxyapatite

In apatitic structures such as Ca 10 (PO 4 ) 6 (OH) 2 , borate groups are introduced as planar and regular BO 3+ 3 and substitute phosphate and hydroxyl groups. In order to study the influence in the change of the coordination environment of the cationic sites on the luminescent properties of RE ions doping calcium borohydroxyapatite, the time-resolved luminescence of the Eu 3+ ion in this new compound is reported. Site-selective excitation of the 5 D 0 level was performed and luminescence decay times of each Eu 3+ site were measured at 77 K. By comparison with Eu-doped boron free apatites, it is shown that borate groups induce perturbations in the Eu 3+ luminescence features. The spectroscopic results are discussed in terms of possible charge compensation mechanisms correlated with the structural data.

Relationships between structural and luminescence properties in Eu3+-doped oxyphosphate–silicate apatite Ca2+xLa8−x(SiO4)6−x(PO4)xO2

The present paper reports the Eu 3+ fluorescence in the continuous solid solution Ca 2+x La 8 x(SiO4) 6-x (PO 4 ) x O 2 (x = 0,3,6) of the apatitic phosphate-silicates M 10 (XO 4 ) 6 Y 2 with M = Ca, La/X = P, Si and Y = O. Selective UV laser excitation, site-selective-laser excitation in the 5 D 0 level have been performed at 300 and 77 K 5 D 0 level decay times have been reported. In, these compounds, Eu 3+ can be observed in the three crystallographic positions Ca(I), Ca(II) and La(II) of the two cationic sites labeled M(I) (4f) C 3 symmetry and M(II) (6h) C s symmetry. The dominant one is found M(II) clue to an Eu - O privileged bonding with Eu 3+ located in (6h) positions either in La(II) or in Ca(II).

Introduction of boron in hydroxyapatite: synthesis and structural characterization

Abstract Apatites doped with rare-earth ions have been extensively studied due to their potential applications as phosphors or laser hosts. The structure of apatite is based on a network of only tetrahedral PO 4 groups. When boron is added, phosphate and OH groups would be partially substituted by borate groups and new calcium borohydroxyapatite with nominal stoichiometry Ca 10 PO 4 6−x BO 3 x BO 3 y BO 2 z OH 2−3y−z is proposed. When P/B ratio=7.22, boron atoms are totally introduced in the apatitic lattice, but from P/B=11 samples are biphased borohydroxyapatite and Ca(OH) 2 and when P/B is lower than 7.22, Ca 3 (BO 3 ) 2 is also observed. The infra-red (IR) and Raman spectroscopy and 11 B MAS (magical angle spinning)–NMR experiments prove that boron is introduced as two-fold coordinated boron BO − 2 in the channels of the apatitic structure and as triangular BO 3− 3 groups substituting PO 4 and OH groups leading to a AB-type borohydroxyapatite. A comparison with a free boron hydroxyapatite shows that P and proton sites are split into several sites in the substituted compounds.

Energy levels of Pr3+ in CsPrP4O12 and RbPrP4O12 cyclotetraphosphates

Abstract Single crystals of CsPrP 4 O 12 and RbPrP 4 O 12 cyclotetraphosphates were grown using the flux method. CsPrP 4 O 12 crystallizes in the cubic I-43d space group whereas RbPrP 4 O 12 crystallizes either in the cubic I-43d or monoclinic C2/c space group. The Pr 3+ ions occupy sites of S 4 and C 2 symmetries in the cubic and monoclinic phases, respectively, with an eightfold coordination in both phases. The present work reports on an analysis of the Pr 3+ 4f 2 energy level diagram based on the low temperature fluorescence spectra under laser selective excitation in the 3 P 2 states of the cubic CsPrP 4 O 12 and monoclinic RbPrP 4 O 12 compounds. The experimental energy levels are fitted using the SPECTRA program available on the Argonne National Laboratory website. The best fits lead to standard deviations in the order of 28 and 21 cm −1 for the CsPrP 4 O 12 and RbPrP 4 O 12 materials, respectively.

Investigation of the CaO–La2O3–SiO2–P2O5 quaternary diagram. Synthesis, existence domain, and characterization of apatitic phosphosilicates

Abstract The CaO–La 2 O 3 –SiO 2 –P 2 O 5 phase diagram was investigated in order to determine a domain inside which all points correspond to pure apatitic oxyphosphosilicates with the general formula Ca x La y (SiO 4 ) 6− u (PO 4 ) u O t . The prepared compounds were chemically analyzed and then characterized by X-ray diffraction method, infrared absorption, and Raman diffusion spectroscopies. The bands present in the IR and Raman spectra were identified and assigned to the corresponding vibration modes of SiO 4 and PO 4 anions. The Eu 3+ luminescence study of some doped samples was carried out and their color points were determined. The present data show that a continuous solid solution is obtained inside the apatitic defined domain. Among the Eu 3+ -doped samples, the Ca 2 La 8 (SiO 4 ) 6 O 2 :Eu(2%) can be used as a red phosphor.

The silver lead apatite Pb8Ag2(PO4)6: hydrothermal preparation

Abstract Stoichiometric silver lead apatite compounds have been obtained by hydrothermal reaction of lead orthophosphate Pb3(PO4)2 and silver orthophosphate Ag3PO4 at 215°C and 100 atm. They were characterized using a variety of analytical techniques (chemical analysis, X-ray diffraction, infrared absorption spectroscopy and Raman scattering spectroscopy).

Synthesis and characterization of new oxyboroapatite. Investigation of the ternary system CaO–P2O5–B2O3

Abstract The CaO–P 2 O 5 –B 2 O 3 phase diagram was investigated at 1200 °C in order to determine the existence domain of pure apatitic oxyborophosphates with the general formula Ca x (PO 4 ) y B z O t . The prepared compounds were chemically analyzed and then characterized by X-ray diffraction, infrared absorption and Raman scattering spectroscopies. 11 B and 31 P magic angle spinning (MAS) NMR experiments suggest that boron is introduced as 2-fold coordinated boron BO 2 − in the channels of the apatitic structure and as triangular BO 3 3− groups in the channels and substituting for PO 4 groups. The present data show that a continuous solid solution is obtained inside the apatitic defined domain.

Crystal growth, structural and spectroscopic characterization of undoped and Yb3+-doped oxyboroapatite fibers

Abstract High quality undoped and Yb3+-doped new calcium oxyboroapatite single crystals were obtained. The samples were grown in monocrystalline fiber form by using a fast and economical floating zone method under laser heating so-called LHPG for laser heated pedestal growth and were characterized by X-ray diffraction, IR spectroscopy and Raman spectroscopy. Yb3+ absorption, emission and fluorescence decay studies were carried out both at low and room temperatures. Electronic energy level positions were interpreted by comparing absorption and emission spectra with those of vibronic sideband energy positions from Raman and IR absorption spectroscopies. Emission spectrum at low temperature and experimental fluorescence decays within ms range reveal Yb3+ ion occupation within at least two different crystallographic sites of the apatite-type structure leading to a broad emission band at room temperature from 925 to 1200 nm, which seems of high interest for ultrashort laser pulse production.

Synthesis and characterization of the hydrated rare-earth acid diphosphates LnHP2O7·3.5H2O (Ln = rare-earth elements)

Hydrated lanthanum acid diphosphates, of the formula LnHP2O7·3.5H2O, have been prepared from acidic LaCl3 and Na4P2O7 solutions (pH = 1), and characterized by XRD, IR and NMR spectroscopic techniques. In the series Ln = La–Sm, these phosphates crystallize in the orthorhombic system (Type I) but in the series Sm–Yb, they crystallize in the triclinic system (Type II). In the case of Sm diphosphates both structures can be obtained depending on the synthesis conditions. The diphosphate character of the compounds was assessed by IR and NMR and two environments, namely PO43− and HPO42−, were identified by 31P MAS spectroscopy. Finally, a different distribution of OH and water was deduced from NMR and IR spectroscopic analysis of the two series of diphosphates.

Etude du diagramme d'equilibre du systeme KPO3-Er(PO3)3 et des formes allotropiques des phosphates condenses KEr(PO3)4

Abstract KPO 3 -Er(PO 3 ) 3 system has been investigated for the first time by DTA, X-ray diffraction and IR spectroscopy. It has shown the existence of one compound KEr(PO 3 ) 4 ( P 2 1 / c ) which melts incongruently at 985 K. A eutectic point appears at 905 K, corresponding to a concentration of 19% molar Er(PO 3 ) 3 . The intermediate compound presents two monocrystalline forms: the former has a chain structure KEr(PO 3 ) 4 ( P 2 1 / c ) ( a = 10.773(5) A, b = 8.838(5) A, c = 12.684(9) A, β = 128°.91(3), Z = 4); the latter has a cyclic anion KErP 4 O 12 ( C 2/ c ) ( a = 8.05(2) A, b = 12.45(2) A, c = 10.72(1) A, β = 109°.8(1), Z = 4). The method of synthesizing single crystals of these compounds is explained, and the diffraction data and IR absorption spectra are given.