Studies on thermal and mechanical properties of monazite-type ceramics for the conditioning of minor actinides

• Single-phase La(1−x)EuxPO4 solid solutions were synthesized hydrothermally.
• The thermal behaviour of the (La, Eu)PO4 powders was investigated.
• Pellets with a high sintering density were obtained after hot pressing.
• The mechanical properties of the pellets depend linearly on the composition.

Lanthanum and europium phosphates with various La/Eu ratios were synthesised using the wet-chemical microwave-assisted hydrothermal method. The thermal behaviour of the (La, Eu)PO4 powders was investigated by thermogravimetric analysis coupled with differential scanning calorimetry (TG-DSC) and X-ray diffraction (XRD). Pelletisation of the phosphates was performed using uniaxial hot pressing at a sintering temperature of 1350 °C. The sintering density for all five compositions reached 98% of the theoretical density. According to XRD data, single-phase solid solutions were obtained in all cases. The physical properties of these pellets were studied. The mechanical properties (microhardness and fracture toughness) of the pellets were observed to be linearly dependent on the europium content.