Encapsulated gadolinium zirconate pyrochlore particles in soda borosilicate glass as novel radioactive waste form

Gadolinium zirconate pyrochlore crystals, with a potential for hosting radioactive elements, were encapsulated in a soda borosilicate glass matrix forming a composite material. The fabrication process involved mixing as a powder followed by hot pressing at a relatively low temperature of 620 °C. Composites containing pyrochlore particles of mean particle size <60 μm in concentration of up to 40 vol% exhibited a homogeneous distribution of the particles in the glass matrix. The absence of debonding of Gd zirconate particles or deflection of cracks during fracture, indicates that a strong interface between the glass matrix and the gadolinium zirconate particles was achieved, which suggests a high mechanical strength and hardness of the composites. Mechanical tests were carried out and it was confirmed that the presence of the gadolinium zirconate particles increased the Young's modulus and fracture toughness of the composite by 35% and >100%, respectively, in comparison with plain borosilicate glass. The results indicate that the new waste forms are superior in terms of structural integrity and fracture behaviour than plain borosilicate glass waste forms.