Specific trends in phosphate glass crystallization

This paper focusses on investigating and comparing the congruent crystallization of phosphate glasses with different degrees of polymerization. The study was performed both on powders, with different size fractions, and coarse particles which can be assimilated to bulk. From DSC experiments, corroborated by SEM analysis, it was demonstrated that LiPO3 crystallizes from surface whereas LiGe2(PO4)3 crystallizes in the whole volume. Sn2P2O7 presented both phenomena, the nucleation time lag being short enough to observe internal crystallization at the laboratory time scale. Using the non-isothermal Ozawa method, the kinetic parameters of the overall devitrification process were determined in terms of the Avrami exponent and of the activation energy for crystallization. The temperature of the maximum nucleation rate was calculated by using the nucleation adiabatic theory. For the achievement of this calculation, the heat capacity temperature dependence up to melting was determined from DSC experiments. The results were found in a good agreement with the SEM observation and the results of the non-isothermal crystallization study.acceptedVersionPeer reviewe

CdCl3− vs CdCl42− in Hybrid Materials

International audienceThe synthesis and the structural of tetrachlorocadmate(II) and trichlorocadmate(II) systems, with perovskite-like structures, are described. The countercations are diprotonated amines, such as the benzidine; monoprotoned amines, the case of Creatinine or amino acids like Histidine. The structural model of the compounds consists of extending organic layers. The holes between these layers are occupied by CdCl4 monomer, Cd2X6 dimer, CdX6 in chain and CdX6 [(CdCl42−) n, (CdCl3−) n] layer, stabilizing the structure through hydrogen bonding. The obtained complexes are: Creatininium tetrachlorocadmate(II), Histidinium trichlorocadmate (II), Hydroxonim trichlorocadmate (II) and Benzidinium tetrachlorocadmate(II)