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Single crystals of SmAl3(BO3)4 were synthesized by the group growth on seeds method. The crystal structure was solved using a single‐crystal experiment and the purity of the bulk material was proved by the Rietveld method. This borate crystallizes in the monoclinic C2/c space group with unit‐cell parameters a = 7.2386 (3), b = 9.3412 (5), c = 11.1013 (4) Å and β = 103.2240 (10)°. IR and Raman spectroscopic analyses confirmed the monoclinic structure of SmAl3(BO3)4. Under 532.1 nm excitation, luminescence spectra exhibit bands assignable to the transitions from 4G5/2 to 6H5/2, 6H7/2, 6H9/2 and 6H11/2. The similarity of the luminescence spectra of the trigonal and monoclinic polymorphs is explained by the minor role of Sm—O bond distortion and the primary role of rotational distortion of SmO6 octahedra. The smaller covalency of the Sm—O bond in alumoborates is deduced in comparison with galloborates. Calorimetric measurements did not reveal high‐temperature structural phase transitions up to a temperature of 720 K. [ABSTRACT FROM AUTHOR]

Yttrium ( Y)-based bioceramics are important materials in radiation therapy and biomedical applications. This paper describes a low-temperature method to prepare yttrium phosphate ( YPO4) and Y-doped calcium phosphate (Y-CaP) microspheres using CaP microspheres as template. The as-formed microspheres were characterized using X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscope, and energy dispersive X-ray spectroscopy, confirming the formation of YPO4 and Y-CaP microspheres. The process was based on the dehydration effect of ethanol to CaP materials and hydrated ions transportation in amorphous CaP microspheres. The procedure, owing to its simplicity, may provide a new sight for the preparation of Y or rare earth elements-based bioceramic materials. [ABSTRACT FROM AUTHOR]

Eu2+ and Mn2+ coactivated β- Ca3( PO4)2 ( TCP) phosphors have been prepared by high-temperature solid-state reaction. The site occupation and photoluminescence properties of Eu2+ and Mn2+ have been identified and discussed in detail. The energy transfer from Eu2+ to Mn2+ in TCP: Eu2+, Mn2+ phosphors has been validated and demonstrated to be a resonant type via a dipole-quadrupole mechanism, and the critical distance ( R C) calculated by concentration quenching method is 21.76 Å. A color-tunable emission from violet-blue to red in TCP: Eu2+, Mn2+ phosphors can be realized via the energy transfer from Eu2+ to Mn2+ ions. [ABSTRACT FROM AUTHOR]

Ce3+-, Tb3+-, and Mn2+-activated Ca9MgNa(PO4)7 (CMNP) phosphors have been prepared by a Pechini-type sol-gel method. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and photoluminescence (PL) and cathodoluminescence (CL) spectroscopy were used to characterize the samples. The energy transfer from Ce3+ to Tb3+ in CMNP phosphors has been demonstrated to be a resonant type by a dipole-quadrupole mechanism, and the Ce3+ to Tb3+ critical distances ( RC) calculated by the concentration-quenching method and the spectral-overlap method are 12.21 and 12.11 Å, respectively. A color-tunable emission in CMNP phosphors can be realized by Ce3+→Tb3+ or Ce3+→Mn2+ energy transfer. White cathodoluminescence has been realized in a single-phase Ca9MgNa(PO4)7 host by codoping with Ce3+, Tb3+, and Mn2+ for the first time with International Commission on Illumination (CIE) chromaticity coordinates (0.319, 0.327). Furthermore, the cathodoluminescence (CL) properties of CMNP:Ce3+/Tb3+/Mn2+ phosphors, including the dependence of the CL intensity on accelerating voltage and filament current, the decay behavior of CL intensity under electron bombardment, and the stability of the CIE chromaticity coordinates, have been investigated in detail. Owing to their good CL properties and good CIE chromaticity coordinates, the as-prepared phosphors have potential application in field emission display (FED) devices. [ABSTRACT FROM AUTHOR]

A diagram representing the phase relationships in the Ca3( PO4)2- CePO4 phosphate system has been developed on the basis of results obtained using thermal analysis ( DTA/ DSC/ TG), X-ray diffraction ( XRD), and scanning electron microscopy ( SEM/ EDS) methods. One intermediate compound with formula Ca3 Ce( PO4)3 occurs in the Ca3( PO4)2- CePO4 system at temperature exceeding 1275°C. The compound melts at 1833°C and has one structural form. In the system a solid solution, having the structure of low-temperature form of calcium phosphate Ca3−3 x Ce x( PO4)2− x (where x is a molar fraction of CePO4), exists. The temperature and concentration range of the solid solution has been determined. It has been shown that the Ca9 Ce( PO4)7 phase should be understood as a limited solid solution with x = 0.25. [ABSTRACT FROM AUTHOR]

Eu3+-doped (1–12 mol%) calcium hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) powders were synthesized by a precipitation method and their photoluminescence (PL) properties were investigated. Eu has a limited solubility in HA and Eu2O3 was detected by X-ray diffraction above 3% doping, whereas a nearly single β-phase was obtained up to 6% doping in TCP but EuPO4 appeared in the 12% Eu-doped specimen. Electron spin resonance measurement confirmed that europium ions exist as Eu3+ in both samples. Eu3+-doped HA exhibited a strong emission at 575 nm with several minor peaks at 610–640 nm and Eu3+-doped TCP had an intense emission at 613 nm with secondary peaks at 590–600 nm, which were consistent with the earlier reports determined at low temperatures. In Eu-doped TCP, the PL intensity increased with increasing calcination temperature without phase transformation. The more the Eu added, the higher the PL intensity obtained in both cases. [ABSTRACT FROM AUTHOR]