Effect of calcination temperature on the fabrication of transparent lutetium titanate by spark plasma sintering

Transparent lutetium titanate (Lu2Ti2O7) bodies were fabricated by spark plasma sintering using Lu2O3 and TiO2 powders calcined from 700 °C to 1200 °C. No solid-state reaction was identified after calcination at 700 °C, whereas single-phase Lu2Ti2O7 powder was prepared at 1100 and 1200 °C. The calcination at 700 °C promoted densification at the early stages of sintering, whereas residual pores at grain boundaries resulted in Lu2Ti2O7 bodies with low transparency. Low-density and opaque Lu2Ti2O7 bodies formed owing to the coarsening of the powder calcined at 1200 °C. The Lu2Ti2O7 body sintered using the powder calcined at the moderate temperature of 1100 °C had a density of 99.5% with the highest transmittances of 41% and 74% at wavelengths of 550 nm and 2000 nm, respectively.