Preparation of luminescent Eu-doped yttria-silicate coupons by spark plasma sintering: Reduction from Eu³⁺ to Eu²⁺

Spark plasma sintering technique was used to densify both Eu-doped and Un-doped yttria silicate powders at temperatures in the range between 1300 and 1400 °C. Shrinkage behavior was investigated for sintering powders into a full-consolidated matrix for both undoped and doped Eu⁺³ yttria silicates powder. Maximum shrinkage rate at sintering temperature of 1000 °C was determined when Eu content is present. Sintering process induced phase transition from X1 to X2 in both undoped and Eu-doped powder. On yttrium silicate powders, only has been observed the typical reddish emission of Eu³⁺ ions (centered at 612 nm), however, after the SPS process, the Eu³⁺ has been reduced to Eu²⁺, showing the typical bluish emission, at 404 and 445 nm, corresponding to the two different atomic positions of Eu²⁺ at the X2 phase.