Eulytite Structure Research Articles

Luminescence properties and host sensitization study of Ba3La(PO4)3:Ce3+ with (V)UV and X-ray excitation

We report on successful synthesis and comprehensive study of luminescence spectroscopic properties and decay kinetics of undoped and Ce3+-doped eulytite structure orthophosphate Ba3La(PO4)3 (BLP) upon excitation with UV-VUV and X-ray photons in a wide temperature range. An intrinsic emission located in the UV range is observed for undoped BLP upon both VUV and X-ray excitation. In turn, emission of Ce3+-doped BLP is represented by interconfigurational 5d-4f transitions arising from Ce3+ ions located in two crystallographic sites which demonstrate average decay time of 22 ns and 40 ns upon intracenter excitation. Pulse X-ray excitation results in appearance of slower (μs or longer) decay components and acceleration of the main 5d-4f emission decay component. Host sensitization of Ce3+ emission is well demonstrated by UV-VUV excitation spectra measurements both at liquid helium and at room temperature. Mechanisms influencing the efficiency and time scale of energy transfer from the host to Ce3+ dopant ions are analyzed and discussed while aiming to estimate the potentials of BLP:Ce3+ for scintillator and X-ray phosphor applications.

Anhydrous Europium Phosphates: A Comprehensive Report on Syntheses, Crystal Structures, and Phase Relations

In the ternary system Eu/P/O the anhydrous phosphates EuII3(PO4)2, EuII3EuIII(PO4)3, EuIII3O3(PO4), EuIIIPO4, EuIII(PO3)3, and EuIIIP5O14 exist at equilibrium conditions (ϑ ≈ 1000 °C). A superstructure model for EuII3EuIII(PO4)3 [Eulytite structure family, Fdd2, Z = 24, a = 14.298(1) Å, b = 42.123(3) Å, c = 10.3887(9) Å] is proposed. The results of single‐crystal X‐ray diffraction (SXRD) studies on EuII10–xEuIIIx(PO4)6O1+x/2 (x ≈ 1.5), EuIII3O3(PO4) and ht‐EuIII(PO3)3 are reported. The crystal structures of the thermodynamically metastable phases EuIII2P4O13 (isotypic to YIII2P4O13) and lt‐EuIII(PO3)3 (isotypic to GdIII(PO3)3) were refined from X‐ray powder diffraction data (XRPD). According to our investigation for the oxide phosphide “EuII4OP2” an europium deficiency has to be assumed according to EuII4–xEuIII2x/3OP2 (x ≈ 1.5).

Luminescence properties and energy migration mechanism of Eu3+ activated Bi4Si3O12 as a potential phosphor for white LEDs

A series of Bi4Si3O12: xEu3+ (0.01 ≤ x ≤ 0.1) continuous solid solution phosphors were explored as novel red-emitting phosphors for white light LED. Bi4Si3O12: xEu3+ phosphors with cubic eulytite structure were prepared by solid-state reaction. The effect of doping concentration on excitation, luminescence spectra, the decay curves and CIE color coordinate of the Eu3+-doped Bi4Si3O12 phosphors were analyzed. We analyzed the dependence of emission intensity on dopant concentration through Van Uitert’s equation simulation. It is identified that the dipole—dipole interaction plays a major role in the mechanism of energy migration of Eu3+ in Bi4Si3O12 phosphor. The critical distance for energy migration was determined to be 19 Å. The self-generated quenching process of Eu3+ in the phosphor was discussed based on the model of self-quenching lifetime in presence of self-trapping. The CIE chromaticity coordinates of the phosphor shift to a pure red region with increase of Eu3+ content.

Thermal expansion of phosphate–sulfates of eulytite structure

New phosphate–sulfates of the next chemical formulae ASr2Eu(PO4)2SO4 (A = K, Rb, Cs), NaBa6Zr(PO4)5SO4, Pb2Mg2(PO4)2SO4, and BaxSr4−x(PO4)2SO4 (0 ≤ x ≤ 4) have been designed and synthesized with the aim of investigating their thermal expansion properties in the low-temperature region. Obtained samples have been characterized with X-ray, IR, DTA, and microprobe electron analyses. Crystal structure and unit cell parameters were derived from the least-squares refinement of powder X-ray diffraction data (eulytite-type, sp. gr. $$I 4 {\bar{\text{3}}}d$$ ). The magnitudes of average linear thermal expansion coefficients vary from 1.1 × 10−5 to 1.7 × 10−5 K−1, which is conducive for application in optics and electronics.

Ba3Tb(PO4)3: Crystal growth, structure, magnetic and magneto-optical properties

Ba3Tb(PO4)3 crystals have been grown by the slow-cooling method and the Czochralski technique for the first time for magneto-optical applications. The single-crystal X-ray diffraction confirms that the compound crystallizes in the cubic system I4¯3d, with eulytite structure with a=10.4484(12)Å, V=1140.6(2)Å3 and Z=4. The hardness of Ba3Tb(PO4)3 crystal is about 5.5Moh. The temperature dependence of the magnetic susceptibility indicated that the Ba3Tb(PO4)3 crystal exhibits paramagnetic behavior over the experimental temperature-range 2–300K. Transmittance spectra and the Faraday rotation have been investigated, which demonstrate that Ba3Tb(PO4)3 crystal shows a higher visible transparency than Tb3Ga5O12 crystal and yields a Faraday rotation comparable to that of Sr3Tb(BO3)3 crystal. Ba3Tb(PO4)3 is therefore a promising material in particular for new magneto-optical applications in the visible region.

Study of phase relationships in the Sr3(PO4)2–CePO4 system. Phase diagram and thermal characteristics of phases

A diagram representing phase relationships in the Sr3(PO4)2–CePO4 phosphate system has been developed on the basis of results obtained by thermal analysis (DTA/DSC/TGA) and X-ray diffraction (XRD) methods. One intermediate compound with the formula Sr3Ce(PO4)3 occurs in the Sr3(PO4)2–CePO4 system at temperatures exceeding 1045 °C. The compound has a eulytite structure with the following structural parameters: a=b=c=10.1655(8) Å, α=β=γ=90.00°, V=1050.46(6) Å3. It's melting point exceeds 1950 °C. A limited solid solution exists in the system, which possesses the structure of a low-temperature form of Sr3(PO4)2. At 1000 °C the maximal concentration of CePO4 in the solid solution is below 20 mol%. The solid solution phase field narrows with increased temperature. There is a eutectic point in the {Sr3(PO4)2+Sr3Ce(PO4)3} phase field at 1765 °C and 15 mol% of CePO4. The melting temperature of Sr3(PO4)2 is 1882±15 °C.

Domain structure and defects of highly ordered Bi4Si3O12 micro-crystals

Highly ordered Bi4Si3O12 micro-crystals were prepared at normal atmosphere. Phase identification of the prepared crystals was accomplished by X-ray diffractometer (XRD). Domain structure and defects were characterized by environmental scanning electron microscopy (ESEM). XRD shows that the obtained micro-crystals are of eulytite structure with chemical formulation of Bi4Si3O12. A highly ordered growth pattern is confirmed due to the faster growth of the {124} faces than that of the {204} faces by ESEM. The growing process of the domain structure is of pollen parent and filial generation pattern. The filial generations of Bi4Si3O12 crystals are generated from the pollen parent. Cracks generate from the defect areas and propagate along the {124} faces due to their lower binding energy under a proper temperature gradient, contributing to the total transcrystalline fracture. It is confirmed that the generation and development of the voids in the crystal grains can be developed when unmatched dimensions of the two opposite faces are formed. And the development of the voids is dependent on the dimensions and orientations of the two opposite faces.

The crystal structure of eulytite Pb 3BiV 3O 12

The crystal structure of Pb 3BiV 3O 12 was solved using single-crystal X-ray diffraction technique. The compound crystallizes in the cubic system I 4 ¯ 3 d (No. 220) with eulytite structure with a = 10.7490(7) Å, V = 1241.95(14) Å 3 and Z = 4. The final R 1 value of 0.0198 ( w R 2 = 0 .0384 ) was achieved for 359 independent reflections during the structure refinement. The Pb 2+ and Bi 3+ cations occupy the special position ( 16c) while the oxygen anions occupy the general position ( 48e) in the crystal structure. Unlike many other eulytite compounds, all the crystallographic positions are fully occupied. The structure consists of edge-shared Pb/Bi octahedra linked at the corners to independent [VO 4] 3− tetrahedra units, generating a eulytite-type network in the crystal lattice.

The crystal structure of eulytite Na3Bi5(PO4)6

The crystal structure of Na3Bi5(PO4)6 was solved using the single-crystal X-ray diffraction technique. The structural refinement has led to a reliability factor of R1=0.0257 (wR2=0.0533) for 428 independent reflections. This compound was found to crystallize in the cubic system (space group I4̄3d) with eulytite structure and the lattice parameters: a=10.097 (4) Å, V=1029.38 Å3, Z=2, Dcalc.=5.43 g cm−3 (Dexp.=5.32(5) g cm−3). The structure is characterized by the existence of one single general position (48a) for oxygen anions and two distinguished positions (16c) occupied by Na+ and Bi3+ cations, respectively. The site occupation factors are equal to 3/8 and 5/8 for sodium and bismuth, respectively. Although all PO distances are identical (1.529(4) Å), the OPO angles ranging from 108.06 (15) to 112.32 (31)°, show that [PO4]3− are rather distorted. Both sodium and bismuth cations are located in octahedral sites with corresponding mean distances of NaO and BiO equal to 2.428 and 2.386 Å, respectively. As expected from the close values of the ionic radii of Na+ and Bi3+, these distances lie in the same range.

The crystal structure of the phosphate eulytite Ba 3Bi(PO 4) 3

Ba 3Bi(PO 4) 3 crystallizes with the eulytite structure and the cubic space group I 4 3 d. X-ray crystallography has allowed us to determine the following crystal data: a = 10.5036(4) Å, V = 1158.8 Å 3, Z = 4, D cal = 5.19 g/cm 3, D exp = 5.02 g/cm 3. The structure was solved on a single crystal, using 343 independent reflections, with R1 = 0.0379 (wR2 = 0.0752). It could be viewed as built up from independent [PO 4] 3– tetrahedra, lying along rods parallel to the axis and to [001]. The rods are arranged in a manner to delimit pairs of irregular pentagonal tunnels. In addition to two oxygen sites identified in the title structure, as previously reported for other compounds, two different sites were refined for barium and bismuth contrary to what has been reported in equivalent eulytite compounds.

Different types of s 2 ion luminescence in compounds with eulytite structure

The luminescence properties of Bi 4Ge 3O 12 (BGO)-related compounds are reported. Pb 4(PO 4) 2SO 4 shows a similar emission of BGO which is ascribed to an activator-perturbed exciton state or the so-called D-level. Compositions diluted with noble gas cations as well as Pb 3Bi(PO 4) 3 show luminescence of s 2 ← sp type on the s 2 ion. A search for new scintillator candidates did not appear to be successful but yielded insight into the luminescence of these compounds.

Cerium(III) luminescence and disorder in the eulytite structure

The Ce 3+ luminescence in several phosphate-containing eulytites is reported and discussed. The dependence of the luminescent properties on the composition of the host lattice is small. This is discussed in terms of the oxygen disorder.

Structural refinements of eulytite-type Ca 3Bi(PO 4) 3 and Ba 3La(PO 4) 3

The room-temperature structures of the eulytite compounds Ca 3Bi(PO 4) 3 and Ba 3La(PO 4) 3 have been refined using powder neutron diffraction data. The metal atoms are disordered on a single site of the I 43d space group, whereas the oxygen atoms are split between two sites, giving rise to rotational disorder of the phosphate anion similar to that previously observed in Sr 3La(PO 4) 3. The degree of oxygen disorder depends on the nature of the metal atoms and, in particular, is reduced when Bi 3+ ions are present in the eulytite structure.

Étude cristallochimique de monophosphates mixtes de bismuth de type eulytite

All the compounds studied can be represented by the general chemical formula M I x M II 12−2 x Bi 4 + x (PO 4) 12 0 ⩽ x ⩽ 6 Many possibilities of cationic substitution have been considered. The eulytite structure seems to be maintained as soon as the cationic radii are greater than 0.97 Å.

Ca 3Ln(PO 4) 3 ( Ln =La-Gd) phases with the eulytite structure

Ca 3Ln(PO 4) 3 ( Ln =La-Gd) phases with the eulytite structure