Formation and aspect ratio control of rhabdophane-type yttrium orthophosphate hexagonal prism particles synthesized by a citrate-assisted hydrothermal process

Abstract

Rhabdophane-type yttrium orthophosphate particles were prepared in an aqueous phase with trisodium citrate (Na₃-Cit) under systematically varied conditions. The obtained rhabdophane-type YPO₄ particles were basically in a hexagonal prism shape, reflecting its hexagonal crystal structure. The prism's width and height differed depending on the reaction conditions. A higher Na₃-Cit concentration led to a lower prism height, whereas a higher pH similarly decreased the width and height. The growth kinetics suggested that the rhabdophane-type YPO₄ particles grew in the surface-reaction-controlled growth mode. The activation energies of the growth, estimated by the Arrhenius plots in the range of 95–120 °C, were slightly different between the width and the height directions, resulting in the temperature-dependent shape of the hexagonal prism. Also, Tb³⁺ ions were doped into the rhabdophane-type YPO₄ particles to observe photoluminescence.