Many people believe that an ionic-diffusion in an ionic crystal is very slow around room temperature. Therefore, a conventional solid-state reaction (SSR) method requires a high temperature to synthesize the ceramic materials. Synthesis of morphology controlled phosphors can be categorized in two ways namely, chemical and physical methods. Various methods such as the sol-gel, hydro-thermal, or the polymerized complex methods are usually used to synthesize phosphor materials. However, these methods require expensive and special experimental equipment, raw materials, or solvents.

In order to perform inexpensive mass-production for new phosphor materials, we have applied novel soft chemical synthesis technique, water-assisted solid-state reaction (WASSR) method. The WASSR method is very simple and can synthesize nano-materials just by storing or mixing raw materials added a small amount (typically 10wt%) of water at low temperature below 500 K. Typical particle sizes (10 - 100 nm) of the samples prepared by the WASSR method were smaller than that (2 - 10 micrometer size) of the sample prepared by the SSR method. The most probable mechanism is new type water accelerated solid acid-base reaction on the surface. We successfully synthesized various phosphor materials ((Cs,Rb)VO₃, YVO₄:Eu, Ba₂SiO₄:Eu, LaPO₄:Ce,Tb) by the WASSR method. In this study, we report the synthesis of non-oxide halide phosphors (CsPbX₃, K₂SiF₆:Mn).

For example, a stoichiometric mixture of CsBr, PbCl₂ was mixed for the WASSR synthesis of CsPbBr₃ quantum dot phosphor. Then, a small amount (10 wt%) of water was added to the mixture and mixed using mortar for 1 min to synthesize a single phase of CsPbBr₃. The XRD pattern of the products are in good agreement with that of single phase CsPbBr₃. The QD dispersed hexane solution shows strong green emission under the excitation of UV light. Our proposed WASSR synthesis technique is a powerful tool for rapid screening and mass-production of phosphor materials.

Acknowledgment

This research was partly supported by the Ministry of Trade, Industry and Energy(MOTIE) and Korea Institute for Advancement of Technology(KIAT) through the International Cooperative R&D program(P0006844_Development of color conversion nanocrystal luminescence materials for next generation display).

References

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