In oxides, the substitution of non-oxide anions (F(-),S(2-),N(3-) and so on) for oxide introduces many properties, but the least commonly encountered substitution is where the hydride anion (H(-)) replaces oxygen to form an oxyhydride. Only a handful of oxyhydrides have been reported, mainly with electropositive main group elements or as layered cobalt oxides with unusually low oxidation states. Here, we present an oxyhydride of the perhaps most well-known perovskite, BaTiO(3), as an O(2-)/H(-) solid solution with hydride concentrations up to 20% of the anion sites. BaTiO(3-x)H(x) is electronically conducting, and stable in air and water at ambient conditions. Furthermore, the hydride species is exchangeable with hydrogen gas at 400 °C. Such an exchange implies diffusion of hydride, and interesting diffusion mechanisms specific to hydrogen may be at play. Moreover, such a labile anion in an oxide framework should be useful in further expanding the mixed-anion chemistry of the solid state.

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The dynamics and structure have been compared for two types of silica gels prepared from tetramethoxysilane in dimethylformamide under acidic and basic conditions. An in-situ time-resolved dynamic light scattering (TRDLS) technique was employed to investigate the changes of the dynamics during gelation process. In both cases, a clear power-law behavior in the time-intensity correlation function, g (2) (τ) -1 ∼ τ n-1 , was observed at the gelation threshold, from which the critical exponent of viscoelasticity, n, was evaluated. The gelation of the acid system was slower, and the gelation time was a weak decreasing function of the initial monomer concentration, C. The resultant gel was found to be made of long polysiloxane chains slightly connected with each other, which was characterized by n ≈ 0.5. On the other hand, the gelation time of silica gels prepared with a basic catalyst was strongly dependent on C. The evaluated value n ≈ 0.73 indicates the presence of highly branched clusters with short strands. It is demonstrated that the TRDLS technique is a powerful tool to investigate gelation process of silica from both dynamic and structural points of view.

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