Fabrication of Lu2Ti2O7-Lu3NbO7 solid solution transparent ceramics by spark plasma sintering and their electrical conductivities

Abstract The Lu2Ti2O7-Lu3NbO7 system, belonging to A2B2O7 with a cubic structure, is attractive for tailored properties by substitution. In this study, Lu2+0.25xTi2−0.5xNb0.25xO7 (x = 0–4) transparent ceramics were fabrication by reactive spark plasma sintering using commercially available Lu2O3, TiO2 and Nb2O5 powders. The phase evolution, microstructure, density, transmittance and electrical conductivity were investigated as a function of composition parameter x. The results showed that Lu2+0.25xTi2−0.5xNb0.25xO7 transparent ceramic had a pyrochlore structure at x = 0 and 1, while preserved a defect-fluorite structure at x = 2–4. The lattice parameter and theoretical density increased linearly, while the average grain size decreased steadily with increasing composition parameter x. All the specimens exhibited a dense microstructure and the highest in-line transmittance was 64% at 550 nm for x = 4. The bulk conductivity increased with increasing x, reaching a maximum value of 4.2 × 10−2 S m-1 for Lu3NbO7 at 1073 K.