The pH-dependent reactions in the sonochemical synthesis of luminescent fluorides: The quest for the formation of KY3F10 crystal phases

In this study Eu3+-doped yttrium fluorides were designed by ultrasound-assisted processes at different pH values (4.0-9.0). This novel strategy has enabled to obtain materials with intriguing morphologies and modulated crystal structures: alpha-KY3F10, delta-KY3F10.xH(2)O, and Y(OH)(3-x)F-x. To date, the literature has primarily focused only on the alpha-phase of KY3F10. Yet, explaining the formation of the mostly uncharted delta-phase of KY3F10 remains a challenge. Thus, this paper offers the key to synthesizing both the alpha and the delta-phases of KY3F10 and also reports the first ultrasound-assisted process for the preparation of yttrium hydroxyfluorides. It is also unraveled the connection between the different pH-dependent reactions and the formation mechanisms of the compounds. In addition to this, the unique features of the Eu3+ ion have allowed to conduct a thorough study of the different materials and have endowed the compounds with photoluminescent properties. The results underscore a highly tunable optical response, with a wide gamut of color emissions (from orangish to red hues), lifetimes (from 7.9 ms to 1.1 ms) and quantum efficiencies (98-28%). The study unveils the importance of sonochemistry in obtaining luminescent fluorides with controlled crystal structures that can open up new avenues in the synthesis and design of inorganic materials.

Automated summary

In this study, Eu3+-doped yttrium fluorides were synthesized by ultrasound-assisted processes at different pH values. The materials obtained exhibited intriguing morphologies and modulated crystal structures, including alpha-KY3F10, delta-KY3F10.xH(2)O, and Y(OH)(3-x)F-x. The study also explored the formation mechanisms of these compounds and investigated their photoluminescent properties, highlighting a highly tunable optical response. The results demonstrate the importance of sonochemistry in the synthesis and design of luminescent fluorides with controlled crystal structures.