Formation features and functional properties of Gd2Ti2O7:Sm3+/Nd3+ nanoparticles synthesized by combined method

Abstract

The present paper is devoted to the investigation of the formation process and growth of Gd₂Ti₂O₇ nanocrystals with a pyrochlore structure doped with Sm³⁺ and Nd³⁺ ions. During the Gd₂Ti₂O₇:Sm³⁺/Nd³⁺ nanoparticles synthesis, aqueous solutions of gadolinium, samarium and neodymium nitrates were added to a mixture of titanium isopropoxide, and polyethylene glycol was diluted with isopropyl alcohol, after which the resulting substance was evaporated to a gel state and heat-treated according to a two-stage scheme. As a result of the study, it has been shown that the forming material had a trabecular structure with a developed network of macro- and micropores. The use of a two-stage heat treatment promotes uniform distribution of different nature atoms in resulting samples. In addition it has been concluded that gadolinium titanate crystalls with a pyrochlore structure is formed by an aggregation mechanism at 700 °C from an X-ray amorphous precursor. From the point of view of obtaining a single-phase material, a possibility of varying nanocrystals dimensions and the pyrochlore structure defectiveness, annealing of the precursor in the temperature range of 750–900 °C is most promising. In this case, the most significant percentage of Sm³⁺ and Nd³⁺ ions, which change their localization with increasing synthesis temperature, are incorporated into the crystal structure of Gd₂Ti₂O₇. Doping of Gd₂Ti₂O₇ nanocrystals not only leads to appearance of expected photoluminescence, but also contributes to manifestation of extraordinary effects in dielectric characteristics of such a material.