Abstract:The phosphor CaTiO 3 :Pr 3+ was synthesized via a solid-state reaction in combination with a subsequent annealing under flowing NH 3 . Comparatively large off-center displacements of Ti in the TiO 6 octahedra were confirmed for as-synthesized CaTiO 3 :Pr 3 by XANES. Raman spectroscopy showed that the local crystal structure becomes highly symmetric when the powders are ammonolyzed at 400 °C. Rietveld refinement of powder X-ray diffraction data revealed that the samples ammonolyzed at 400 °C have the smallest lattice strain and at the same time the largest average Ti-O-Ti angles were obtained. The samples ammonolyzed at 400 °C also showed the smallest mass loss during the thermal re-oxidation in thermogravimetric analysis (TGA). Enhanced photolumincescence brightness and an improved decay curve as well as the highest reflectance were obtained for the samples ammonolyzed at 400 °C. The improved photoluminescence and afterglow by NH 3 treatment are explained as a result of the reduced concentration of oxygen excesses with simultaneous relaxation of the lattice strain. 2670-2673 (1996). 3. B. M. J. Smets, "Phosphors based on rare-earths, a new era in fluorescent lighting," Mater. Chem. Phys. 16(3-4), 283-299 (1987 44(6), 815-818 (1982). 38. M. Stachiotti, A. Dobry, R. Migoni, and A. Bussmann-Holder, "Crossover from a displacive to an order-disorder transition in the nonlinear-polarizability model," Phys. Rev. B Condens. Matter 47(5), 2473-2479 (1993). 39. A. Bussmann-Holder, A. R. Bishop, and G. Benedek, "Quasiharmonic periodic traveling-wave solutions in anharmonic potentials," Phys. Rev. B 53(17), 11521-11530 (1996). 40. E. A. Stern, "Character of order-disorder and displacive components in barium titanate," Phys. Rev. Lett. 93(3), 037601 (2004). 41. P. Boutinaud, E. Pinel, M. Dubois, A. P. Vink, and R. Mahiou, "UV-to-red relaxation pathways in CaTiO3:Pr 3+ ," J. Lumin. 111(1-2), 69-80 (2005 ©2013 Optical Society of America

Supporting InformationFig S1, S2. X-ray powder diffraction of initial Ca(BH 4 ) 2 and Ca(BD 4 ) 2 formed after isotope exchange. Both samples are mixtures of α, β, and γ phase of Ca(BH 4 ) 2 .(see text)

High-pressure Raman spectroscopy has been used to study tris(hydroxymethyl)aminomethane (C(CH(2)OH)(3)NH(2), Tris). Molecules with globular shapes such as Tris have been studied thoroughly as a function of temperature and are of fundamental interest because of the presence of thermal transitions from orientational order to disorder. In contrast, relatively little is known about their high-pressure behavior. Diamond anvil cell techniques were used to generate pressures in Tris samples up to approximately 10 GPa. A phase transition was observed at a pressure of approximately 2 GPa that exhibited relatively slow kinetics and considerable hysteresis, indicative of a first-order transition. The Raman spectrum becomes significantly more complex in the high-pressure phase, indicating increased correlation splitting and significant enhancement in the intensity of some weak, low-pressure phase Raman-active modes.

The pressure/temperature phase diagram of LiAlH 4 has been constructed by using Raman spectroscopy data. In situ high pressure-temperature experiments were carried out using resistively heated diamond anvil cells up to 150 °C and 7 GPa. Room temperature phase transitions of monoclinic R-LiAlH 4 f δ-LiAlH 4 were observed at ∼3.2 GPa. As the temperature is increased to ∼100 °C, both the R and δ phases transform to β-LiAlH 4 and remain stable up to 5.5 GPa. At temperatures greater than 300 °C, a new γ-LiAlH 4 phase forms. Data of Konovalov (1995) has been used to define the phase boundary between βand γ-LiAlH 4 phases. We present a pressure-temperature phase diagram of LiAlH 4 based using diamond anvil cells coupled with Raman spectroscopy.