CdS and PbS semiconductor nanoclusters (2 - 10 nm) are produced by using direct precipitation, (gamma) -radiolysis and reversed micelles. A chemical capping reaction is made at the cluster surface by thiolate complexes. The structure and the size of the capped clusters are determined by Optical Absorption, X-ray Diffraction, Small Angle X-ray Scattering and High Resolution Electron Microscopy. After grafting of a gel precursor at the cluster surface, PbS and CdS particles can be incorporated in optically clear and dense oxide gels prepared by hydrolysis of metal alkoxides in a wet atmosphere.

Various organic dyes have been embedded in matrices of transparent silica porous glasses prepared at room temperature by the sol-gel technique (1). The basic reaction of this process is an inorganic polymerization between silanol reactive monomers (≡Si-OH). These inorganic hosts are a link between organic and high temperature inorganic glasses. Hole-burning measurements have been published previously on chlorin and oxazine-4 perchlorate in a silicate glass (2).

We report the structure, the phase transitions, and the transport properties of two different phases of LiZr2(PO4)3 materials prepared by the sol/gel technique. The phases have been characterized by X-ray powder diffractometry, thermal analysis, ac conductivity, and NMR (31P and 7Li). A high-temperature phase, prepared at 1200°C, shows a NASICON-type structure and a monoclinic → rhombohedral first order transition at about 40°C. This transformation is associated with the sharp appearance of a lithium motion leading to high conducting properties above the phase transition σ = 1.2.10−2 (Ω cm)−1 at 300°C. A low-temperature phase, prepared at 900°C, exhibits the β-Fe2(SO4)3-type structure and a monoclinic → orthorhombic transformation at 300°C. A local lithium motion progressively takes place between RT and 120°C and a conducting state is observed at 300°C (σ = 5.10−4 (Ω cm)−1). In diphasic samples prepared between 900 and 1200°C, both resistivity and activation energy progressively increase with the low-high temperature phase ratio.