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We have investigated mixed electronic‐ionic conduction in 0.5[xAg2O·(1 −x)V2O5]–0.5TeO2 glasses, where the Ag2O amount varies over a range of 5–40 mol%. The glass samples have been prepared by quenching the melt. The ac conductivity has been measured at frequencies from 10 Hz to 100 kHz and temperatures of 300–425 K. The data indicate that the conduction mechanism changed from being predominantly electronic to ionic for Ag2O contents of >27.5 mol%. This transition is due to the change in glass structure, which affects both electronic‐ and ionic‐transport properties. The electronic dc conductivity results have been analyzed in terms of a small polaron‐hopping model.

We demonstrate that suitable thermal treatment of biocompatible CaO-Na 2 O-P 2 O 5 -SiO 2 glasses prepared by the usual melt-quench results in spinodal phase separation and crystallization of phases at very different length scales. Selective chemical leaching of these phases allows the formation of interconnected multi-modal porosity, with pore size ranging from several nanometers to tens of micrometers. Such novel nano-macroporous glasses have potential applications as superior bioscaffolds.E. Zanotto-contributing editor z Pores are classified as microporous (diameter o2 nm), mesoporous (2odiameter o50 nm), and macroporous (diameter 450 nm). 7

We have investigated the evolution of the structure of nanomacro porous CaO-Na 2 O-P 2 O 5 -SiO 2 bioactive glassceramics by Fourier transform infrared (FTIR) and Raman spectroscopies, and X-ray diffraction (XRD). A controlled devitrification, followed by a chemical leaching treatment is used to produce a multimodal distribution of nano/macro pores that are expected to improve cell attachment. Data show that the leaching process removes the sodium-and calcium-containing crystalline phases that are formed during the ceramming heat treatment. The primary Si-O peaks in the infrared spectra blue shift with leaching, indicating that the sample becomes SiO 2 rich. In parallel, the fraction of nonbridging oxygen decreases. These results suggest a restructuring of the glass network far below the glass transition temperature. The stresses from leaching, capillary forces, and subsequent restructuring develop and grow, eventually producing cracks in the sample.