CC BY
3The effect of HIP on the microstructure and luminescent properties of SPS AhO3-Ce:YAG composites
A.A. Vornovskikh1*, O.O. Shichalin1, A.P. Zavjalov1, S.S. Balabanov2, D.Yu. Kosyanov1
1-Far Eastern Federal University, 10 Ajax Bay, Russky Island, Vladivostok 690922, Russia 2- G.G. Devyatykh Institute of Chemistry of High-Purity Substances of the RAS, 49 Tropinin str.,
Nizhny Novgorod 603137, Russia
The use of laser diodes (LDs) as excitation sources makes it possible to obtain white light with a high lumen density. A^O3-Ce:YAG composite ceramic phosphors are considered as promising components of white LDs. At the same time, fine-grained composites show better applicability when combined with LDs in the reflection mode, where the proper scattering ability of the phosphor plays a key role.
Spark plasma sintering (SPS), as one of the high-speed consolidation techniques under pressure, is considered a proven one-step method for producing opto-functional ceramics with fine microstructure and some inherent residual porosity. An additional hot isostatic pressing (HIP) step is being considered as a way to improve the optical properties of such ceramic materials.
A series of AhO3-Ce:YAG (0.05-0.3 at% Ce3+) composite ceramics were obtained using the individual SPS technique and its combination with HIP post treatment. The HIP stage contributed to some homogenization of the secondary phase grains in the garnet matrix, while reducing their dispersion. The average grain sizes of the constituent phases YAG and AhO3 were ~4 ^m and ~2 ^m, respectively.
The SR luminescence spectra and luminescence kinetics were studied at the wavelength 535 nm of Ce:YAG. The maximum intensity was achieved at 0.2 at% Ce3+, the effect of HIP on the position of the Ce:YAG line is insignificant - a monotonic increase of ~527-534 nm is observed at 0.05-0.3 at% Ce3+. The luminescence kinetics was characterized by two decay modes. An increase in the decay time of ~0.7-3.0 ns and a monotonic decrease in its fraction from ~22-35 to ~14% were observed with increasing Ce3+ content for the fast mode, while increasing the time from ~20-30 to ~47-57 ns for the slow mode.
The luminous properties of phosphors were attestated as a function of the input 454 nm LD power density in reflection mode. Laser-induced luminescence saturation was not observed up to 14 W/mm2. LF (LE) and CCT (CRI) values of 3300-3260 lm (212-210 lm/W) and 7352-5700 K (58-52), respectively, were obtained for 1 mm-thick Al2O3-Ce:YAG (0.1-0.3 at% Ce3+) SPS+HIP-composites.
Acknowledgements: This work was supported by the Russian Science Foundation (No. 20-73-10242). The SR measurements were done at the shared research center SSTRC on the basis of the VEPP-4-VEPP-2000 complex at the Budker Institute of Nuclear Physics SB RAS.
