Fabrication and electrical conductivity of Lu2(Ti1-x Hf x )2O7 transparent ceramics prepared by spark plasma sintering

Abstract

ABSTRACT Lu2(Ti1-x Hf x )2O7 (x = 0–0.5) transparent ceramics were fabricated by reactive spark plasma sintering using commercially available Lu2O3, TiO2 and HfO2 powders. Effect of Hf content x on the phase evolution, microstructure, density, transmittance and electrical conductivity of the resulting ceramics were investigated. Lu2(Ti1-x Hf x )2O7 transparent ceramic had a pyrochlore structure in the range of x = 0–0.3, while preserved a defect-fluorite structure at x = 0.4–0.5. The lattice parameter and theoretical density increased linearly with increasing Hf content x. The average grain size decreased at x = 0–0.3 and kept almost constant at x = 0.4–0.5. All the samples exhibited a dense microstructure and the highest in-line transmittance was 57% at 550 nm at x = 0. The highest bulk conductivity was 1.7 × 10−2 S m−1 at 1073 K for Lu2(Ti0.8Hf0.2)2O7, with an activation energy of 1.16 eV.