In recent years pyrochlores (A₂B₂O₇) have gained considerable interest due to their stability and potential to host rare-earth ions, thus allowing its use in various luminescence-related applications. One of them is lanthanum zirconate pyrochlore (La₂Zr₂O₇) which is known for its reluctance to sintering (therefore it can be used as a thermal barrier coating). The densification of transparent La₂Zr₂O₇ ceramics usually requires high temperatures ~1800 °C and dwell times ~6 h in vacuum or somewhat lower temperatures ~1700 °C in oxygen atmosphere but for longer time >20 h. In this contribution we present a new method for the complete densification of Eu:La₂Zr₂O₇ (3 at.% of Eu) up to transparency at considerably lower temperature (1500 °C) with a total processing time of 5 h (heating and cooling included) under pressure of 80 MPa by spark plasma sintering (SPS) with the help of LiF as a sintering additive. After annealing, the emission spectrum was in the range of 585–625 nm with a lifetime of 2.2 ms. The addition of LiF reduces the on-set temperature of densification by ~300 °C and enhances densification kinetics, however, it promotes grain growth as well. Comparison sample prepared via the same schedule but without LiF addition was not transparent.

Acknowledgement: This work is part of the project GA22-14200S “Low-phonon energy transparent ceramic luminophores emitting in the short- and mid-infrared region”, funded by the Czech Science Foundation (Grantová agentura ?eské republiky / GA?R).