Synthesis and characterization of tin containing molybdophosphate and tungstophosphate glasses

Two series of tin containing molybdophosphate and tungstophosphate glasses and glass–ceramics were achieved by means of a domestic microwave oven under air. During melting, a redox reaction takes place between Sn2+ and Mo6+ generating the crystallization of a Na(SnIV,MoIV)(PO4)3 solid solution with a NZP (NaZr2P3O12) type structure. Such reactivity was not underlined in the case of the W-series. All the samples were characterized from a thermal and mechanical point of view as a function of the RO3 (R = Mo, W) for SnO substitution. Two types of behaviors were identified. For the Mo-series, all the characteristics, except density, present an extremum value for the chemical composition with a 1:1 SnO–MoO3 molar ratio. This is strongly correlated to the amount of NZP crystals present in the glass ceramic, the different behavior observed for the density being due to the low compactness of the NZP phase. For the W-series, all these different characteristics varies monotonously according to a progressive strengthening of the network by replacement of a low field strength ion (Sn2+) by a higher field strength ion (W6+). In addition, the solid state reactivity of a 1:1 SnO–RO3 mixture was examined confirming the absence of any redox process between SnO and WO3 during the glass synthesis.