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Magnesium whitlockite (Mg-WH, Ca18Mg2(HPO4)2(PO4)12) is a promising candidate for biomedical application in bone regeneration; however, the fabrication of Mg-WH bioceramics by conventional methods is limited. Mg-WH is known to be...

3 . -The title phase is synthesized from stoichiometric mixtures of Bi2O3, MgO, and TiO2 (5-6 GPa, 1270-1370 K) and characterized by powder XRD, EDX, and SEM. The compound crystallizes in the orthorhombic space group Pnnm with Z = 8 and exhibits a superstructure associated with both the antiferroelectric-like displacements of Bi 3+ cations and the antiphase tilting of oxygen octahedra. A relation of the crystal structure of the title phase to that commonly accepted for antiferroelectric perovskite PbZrO3 is discussed. -(KHALYAVIN*, D. D.; SALAK, A. N.; VYSHATKO, N. P.; LOPES, A. B.; OLEKHNOVICH, N. M.; PUSHKAREV, A. V.; MAROZ, I. I.; RADYUSH, Y. V.; Chem. Mater. 18 (2006) 21, 5104-5110; Dep. Ceram. Glass Eng., Univ. Aveiro, P-3810 Aveiro, Port.; Eng.) -W. Pewestorf 02-020

Low‐frequency dielectric response of air‐ and oxygen‐sintered ceramics with the composition 0.9BaTiO3–0.1La(Mg1/2Ti1/2) O3 (0.9BT–0.1LMT) has been studied in the temperature range of 12–550 K. In comparison with pure BT, in 0.9BT–0.1LMT the dielectric permittivity maximum is shifted by almost 300 K toward lower temperatures. Both real and imaginary parts of dielectric permittivity of the solid solution, in the range 12–150 K, show a strong frequency‐dependent behavior, which is typical of relaxors. On the basis of the model of exponential cluster size distribution and the Cole–Cole equation, the degree of interaction between the polar clusters was estimated. It was shown that the oxygen vacancies arising during sintering at high temperatures did not affect noticeably the relaxor properties of the material. The role of heterovalent La3+/Ba2+ and Mg2+/Ti4+ substitutions in the relaxor behavior formation is discussed.

We report that luminescence of Eu 3+ ion incorporated into Ruddlesden-Popper phases allows monitoring phase transition in powders (instead of single crystals), in a time efficient manner (compared to neutron diffraction), and importantly, with greater sensitivity than previous methods. Crystal structure and dielectric response of undoped and 0.5%Eu 3+-doped Sr 3 Sn 2 O 7 ceramics were studied as a function of temperature over the temperature range of 300-800 K. The luminescence studies of 0.5%Eu 3+-doped Sr 2 SnO 4 and Sr 3 Sn 2 O 7 samples were performed in the temperature range of 80-500 K. These results were compared with the respective dependences for the undoped compounds. The structural transformations in 0.5%Eu 3+-doped Sr 3 Sn 2 O 7 were found at 390 and 740 K. The former is associated with the isostructural atomic rearrangement resulted in a negative thermal expansion along two of three orthorhombic crystallographic axes, while the latter corresponds to the structural transition from the orthorhombic Amam phase to the tetragonal I4/mmm one. A similar temperature behavior with the structural transformations in the same temperature ranges was observed in undoped Sr 3 Sn 2 O 7 , although the values of lattice parameters of the Eu 3+-doped and undoped compounds were found to be slightly different 2 indicating an incorporation of europium in the crystal lattice A dielectric anomaly associated with a structural phase transition was observed in Sr 3 Sn 2 O 7 at 390 K. Optical measurements carried out over a wide temperature range demonstrated a clear correlation between structural transformations in Eu 3+doped Sr 2 SnO 4 and Sr 3 Sn 2 O 7 and the temperature anomalies of their luminescence spectra; suggesting the efficacy of this method for the determination of subtle phase transformations.