Microwave-assisted synthesis followed by a reduction step: making persistent phosphors with a large storage capacity

Abstract

Microwave irradiation leads to highly homogeneous emitting sites, and large storage capacity in persistent luminescence materials after the reducing step.

Microwave-Assisted Preparation of Luminescent Inorganic Materials: A Fast Route to Light Conversion and Storage Phosphors

“…In the CSS method, a high-temperature, direct reaction is expected where the solid reactants, with different grain sizes and randomly oriented surfaces, must react through ionic diffusion. The drawback of the solid-state reactions is the limited flux of diffusing species of precursors, impeding crystal growth and forming the final products [ 57 ]. The combination of low ionic diffusion with large temperature gradient during the resistive heating translates to long synthesis’ time at high temperatures (>1000 °C) to avoid inhomogeneous materials with poor optical properties.…”

“…In 2020, Carvalho et al [ 57 ] studied the MASS synthesis of Sr 2 MgSi 2 O 7 :Eu 2+ , Dy 3+ persistent phosphors and microwave irradiation’s effects on the homogeneity and storage capacity. Comparing the conventional and microwave-assisted methods on obtaining the Sr 2 MgSi 2 O 7 :Eu 2+ , Dy 3+ shows that the MASS method provides higher dopant homogeneity in the crystal due to increased ionic diffusion induced by microwave irradiation.…”

“…For instance, solid-state methods benefit significantly from dielectric heating, shortening the synthesis time from days and hours to tens of minutes. In addition, it can yield more uniform, homogeneous materials [57]. The principles of microwave heating are based on the material's response to the electromagnetic fields' alternating nature.…”

“…For instance, solid-state methods benefit significantly from dielectric heating, shortening the synthesis time from days and hours to tens of minutes. In addition, it can yield more uniform, homogeneous materials [ 57 ].…”

“…For luminescent materials, this property is of utmost importance once the homogeneous dispersion of activator and sensitizer ions in the material’s host leads to higher quantum yields and increased brightness [ 67 ]. Homogeneous luminescent materials offer a more-defined local structure that can lead to a precise control of the emitting color of crystal field-sensitive ions, such as Eu 2+ [ 57 ].…”