Borohydrides are actively considered as potential hydrogen storage materials. In this context fundamental understanding of breaking and forming B-H bond is essential. Isotope exchange reactions allow isolating some parts of this reaction without introducing major structural or chemical changes. Experiments were performed on Ca(BH₄)₂and Ca(BD₄)₂ as a function of temperature and pressure. A complete exchange can be realized in about 9h at 200 °C using a deuterium pressure of 20 bar. The activation energy, estimated using first order kinetics, for the forward reaction (Ca(BH₄)₂ → Ca(BD₄)₂) was found to be 82.1 ± 2.7 kJ/mol (P = 35 bar) and the one for the backward reaction (Ca(BD₄)₂ → Ca(BH₄)₂) was found to be 98.5 ± 8.3 kJ/mol (P = 35 bar). Pressure dependent study shows that the reaction rate increases with increasing pressure up to 35 bar. This behavior is consistent with first adsorption step prior to diffusion into the solid and isotope exchange according to the scheme described below.

The phosphor CaTiO₃:Pr³⁺ was synthesized via a solid-state reaction in combination with a subsequent annealing under flowing NH₃. Comparatively large off-center displacements of Ti in the TiO₆ octahedra were confirmed for as-synthesized CaTiO₃:Pr³Â 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 NH₃ treatment are explained as a result of the reduced concentration of oxygen excesses with simultaneous relaxation of the lattice strain.

The pressure/temperature phase diagram of LiAlH₄ 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 α-LiAlH₄ → δ-LiAlH₄ were observed at ~3.2 GPa. As the temperature is increased to ~100 °C, both the α and δ phases transform to β-LiAlH₄ and remain stable up to 5.5 GPa. At temperatures greater than 300 °C, a new γ-LiAlH₄ phase forms. Data of Konovalov (1995) has been used to define the phase boundary between β- and γ-LiAlH₄ phases. We present a pressure−temperature phase diagram of LiAlH₄ based using diamond anvil cells coupled with Raman spectroscopy.