Najia Kbir-Ariguib

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.

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.

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).

Treatment of Tunisian salt lakes using solubility phase diagrams

The Tunisian salt lakes are considered as an important materials resource useful for industry and agriculture. They are called sebkhat or chott, and they cover a large part of Tunisian land. Their brines correspond to the quinary system: Na+, K+, Mg2+ / Cl, SO42H2O. In the first part of this paper, a short description and abstracted geochemical and economical data about some Tunisian salt lakes are given. In the second part, the fitting equations used for modeling the quinary system are established and applied to the subsystems NaClKClH2O, NaClMgCl2H2O, KClMgCl2H2O, and to NaClNa2SO4H2 O, KClK2SO4H2 O, Na2SO4K2SO 4H2O. The coherence between the calculated and the experimental diagrams is discussed.

Etude des equilibres solide—liquide des systemes binaires MIPO3LaP3O9 (MI=Rb, Cs) donnees cristallographiques sur MIxLa(PO3)3+x(x=1, 2)

Abstract RbPO3LaP3O9 and CsPO3LaP3O9 systems have been investigated for the first time by DTA and X-ray diffraction, showing the existence of four new compounds: MIxLa(PO3)3+x (MI= Rb, Cs; x =1, 2) with incongruent melting. For RbLa(PO3)4 four crystalline forms were found, two with chain structure: γ-RbLa(PO3)4 (a=10.592(6); b=9.089(2); c=10.940(2) A; β=105.83(3)°; P21/n; Z=4); β-RbLa(PO3)4 (a=8.815(2); b=9.331(4); c=7.187(4) A; β=99.72(3)°; P21; Z=2); and the other with a cyclic structure: δ-RbLaP4O12 (a=15.302(6) A; I 4 3d; Z=12); α-RbLaP4O12 (a=7.955(2); b=12.842(2); c=10.919(1) A; β=112.33(2)°; C2/c; Z=4). The compound CsLa(PO3)4 presents three crystalline forms: two with chain structure: γ-CsLa(PO3)4 (a=10.664(3); b=9.264(4); c=11.265(7) A; β=106.08(5)°; P21/n;Z=4); β-CsLa(PO3)4 (a=8.878(5); b=9.290(5); c=7.249(6) A; β=98.75(8)°; P21; Z=2); and the other with a cyclic structure: δ-CsLaP4O12 (a=15.382(5) A; I 4 3d; Z=12). The compound Rb2La(PO3)5 has a triclinic unit cell with parameters a=7.259(2); b=13.363(8); c=7.260(2) A; a=90.30(2)°, β=107.40(3)°, γ=89.90(1)°; P1; Z=2. The method of preparation of all these compounds, powder diagrams and IR absorption spectra are given.

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.

Etude du diagramme d’equilibre du systeme NaPO3−Pr(PO3)3

The NaPO3−Pr(PO3)3 system was studied by microdifferential thermal analysis (DTA), IR and X-ray diffraction spectroscopies. The only new compound observed in the system is NaPr(PO3)4, which melts incongruently at 1149 K. A eutectic appears at 5% Pr(PO3)3 at 901 K. The new compound NaPr(PO3)4 was characterized by means of powder X-ray diffraction and IR absorption spectroscopy. NaPr(PO3)4 is a NaLa(PO3)4 isotype; it crystallizes in the monoclinic system P21/c witha=12.328(7),b=13.130(5),c=7.231(5) Å, β=126°, 18(5),Z=4,V=945 Ȧ3.ZusammenfassungMittels Mikrodifferential-Thermoanalyse (DTA) und Röntgendiffraktion wurde das System NaPO3−Pr(PO3)3 untersucht. Die einzig neue, in diesem System beobachtete Verbindung ist NaPr(PO3)4 mit einem inkongruenten Schmelzpunkt bei 1149 K. Ein Eutektikum tritt mit 5% Pr(PO3)3 bei 901 K auf. Die neue Verbindung NaPr(PO3)4 wurde mit Hilfe des Debye-Scherrer-Verfahrens und der IR Absorptionsspektroskopie charakterisiert. NaPr(PO3)4 ist ein Isotyp von NaLa(PO3)4; es kristallisiert im monoklinen System P21/c mita=12.328(7),b=13.130(5),c=7.231(5)Å, β=126, 18(5),Z=4,V=945 Ȧ3.

Thermodynamic Study of the Solid-Liquid Equilibria in the Systems MIPO3-Pr(PO3)3 (MI=Na, Rb, Cs OR Ag)

A previously established equation of a stoichiometric phase liquidus curve was applied to determination of the phase diagrams of the systems MIPO3-Pr(PO3)3 (with MI=Na, Rb, Cs or Ag).The temperature, enthalpy and entropy of fusion were calculated for each solid phase with the exception of silver polyphosphate, the crystallization field of which was very limited.The enthalpy of fusion of the polyphosphate Pr(PO3)3 was determined from the DTA curve.The melting enthalpy of Pr(PO3)3 calculated from the different binary systems was approximately equal to the measured value. The calculated temperatures and compositions were in good agreement with those determined experimentally.

MODELLING OF MULTICOMPONENT SALT SYSTEMS Application to sea water and brines I. Derivation of the model

Abstract The solubility of a salt in saturated solution is described in terms of heterogeneous reaction between solid and liquid and an equation of the solubility field is established for each solid phase (limiting or intermediate phase) of a multicomponent aqueous salt system. The model supposes that solid phases are stoichiometric and that the solution is a strong electrolyte. It includes all sub-systems and the procedure used for the calculation of coefficients is described. The equations allow the critical evaluation of solubility data, the calculation of phase diagrams and the determination of equilibrium (proportion and nature of phases) under any conditions of temperature and composition. The application to the sub-systems involved in sea water and natural brines will be developed in forthcoming publications.

Solid-Liquid Equilibria of the Ternary System Na+, Mg++ // Cl--H2O at 10°C

The isothermal section at 10°C of the solubility diagram of the ternary system Na+, Mg++// ClH2O was established by conductimetric and analytical measurements.Two solid phases, NaCl and MgCl2·6H2O are observed. The solubility range of NaCl is large, while the liquidus curve of MgCl2·6H2O is very short.The composition of the eutonic point, determined by two methods was: 0.32 g% NaCl and 33.80 g% MgCl2.