Thermal Degradation of Polyoxotungstates—An Effective Method for the Preparation of Tungsten Bronzes

Tungsten bronze-based nuclear waste form ceramics. Part 1. Conversion of microporous tungstates to leach resistant ceramics

“…Only the SNL-A and the pollucite have high leach resistance. So far there have been no reports of the use of tungsten bronze compounds for the immobilization of radio cesium although Pope et al [35] have reported on the formation of rare earth cubic bronzes formed from polyoxometallates (arsenates and phosphates) as possible waste form materials. These workers have proclaimed high leach resistance for such phases but as yet have shown no performance data [35][36][37][38].…”

“…So far there have been no reports of the use of tungsten bronze compounds for the immobilization of radio cesium although Pope et al [35] have reported on the formation of rare earth cubic bronzes formed from polyoxometallates (arsenates and phosphates) as possible waste form materials. These workers have proclaimed high leach resistance for such phases but as yet have shown no performance data [35][36][37][38]. Bessonov et al [39] have flagged the interesting idea of using lanthanide cubic tungsten bronze materials as Cs transmutation hosts and made mention to durability but again did not provide any performance data.…”

X-Ray and Electron Microscopy Studies of Rare-Earth Tungsten Bronzes

“…Syntheses of tungsten bronzes at lower temperatures (o9001C) by means of thermal degradation of polyoxotungstates have recently been reported by Wasserman et al (5). They found from X-ray analysis studies of the products that a cubic tungsten bronze of cerium (III), Ce x WO 3 , was formed for x=0.066-0.162.…”

High Temperature Behaviour of Polyoxometalates Containing Lanthanides

“…Recent studies suggest a possibility of a heating process of polyoxometalates (POM) at a temperature significantly lower than the classical methods to obtain tungsten bronzes, MxWO 3 (M: alkali, alkaline earth and rare earth, x: between 0 and 1) containing lanthanide [1], which may be applied for nuclear waste immobilisation [2].…”

“…It is known that one of the tungsten bronzes, ZrW 2 O 8 possesses a negative thermal expansion property [3]. Such a time and energy consuming process could be simplified by using POM as precursors which would be thermally decomposed at lower temperatures and for shorter times yielding the same results [1,2]. Until recently the synthesis of tungsten bronzes containing lanthanides has required extensive heating e.g.…”