Ultrasonic-assisted hydrothermal synthesis of nanoscale double ceric phosphates

The combination of ultrasonic exposure on ceric phosphate gels with subsequent hydrothermalmicrowave treatment resulted in the formation of nanoscale NH$_4$Ce$_2$(PO$_4$)$_3$ or KCe$_2$(PO$_4$)$_3$ phases. The sun protection factor (SPF) and protection factor against UV-A radiation (UVAPF) values for double ceric phosphates with the smallest crystallite sizes exceeded 4 and 3.5, respectively, which is much higher than the values for samples consisting of larger particles. These results are superior to previously published values for similar ceric compounds, and thus show promise for their application in sunscreens.