Chemistry, Physics and Technology of Surface

ISSN 2518-1238 (Online), ISSN 2079-1704 (Print)

For obtaining perovskite-type nanopowders LaYO₃:R, where R = Yb³⁺, Nd³⁺, Eu³⁺ nanopowders under different conditions of precursor synthesis and with various luminescent additive content were synthesized and investigated.

The obtained LaYO₃:R, where R = Yb³⁺, Eu³⁺, Nd³⁺ precursors are homogeneous, mesoporous, nanodispersed, amorphous crystalline powders. Dependent on the synthesis conditions and on the nature of the luminescent additive (Yb³⁺, Eu³⁺, Nd³⁺), precursors with different porous structure (corpuscular or layered), and specific surface area from 50 to 200 m²/g are formed. If luminescent additives Yb³⁺, Nd³⁺ are used, the average diameter of the mesopores of the precursors is 3.3–3.5 nm. The use of Eu³⁺ results in an increase of average diameter up to 6 nm. According to the calculations, the average particle size of the obtained precursor powders is 17–50 nm. The LaYO₃:R precursors are formed as agglomerates of various sizes, shapes and densities. The average size of the agglomerates is 500 nm – 1 μm. The agglomerates have a dense particles packing with almost identical sizes of 15–17 nm.

The maximum specific surface area of the synthesized precursors depends on the amount and type of luminescent additive. The smaller the ionic radius of the luminescent additive, the more it must be added to obtain the maximum specific surface area of the precursor. Thus, when adding Yb³⁺, the maximum specific surface area is reached at 4 vol. %, while with Nd³⁺ it is at 1 vol. %.

Dependent on the amount of Yb³⁺ luminescent additive, porous structures of different types are formed under the same precursor synthesis conditions: layered (3 vol. % Yb³⁺) and corpuscular (4 vol. % Yb³⁺). The specific surface area of the synthesized precursors with different percentages of Yb³⁺ is almost the same, but the total pore volume is significantly different. Co-precipitation with different solution temperatures produces powders with different densities. Thus, at the temperature of 40 °C a dense structure with the pore size of 3–5 nm between the particles of 17–20 nm is formed, and at 80 °C a structure is formed in which the pores and particles are close in size and the pore volume increases more than three times. In addition, raising the synthesis temperature of LaYO₃:Yb precursors with the content of Yb³⁺ 4 vol. % leads to the formation of a predominantly layered structure that characterizes the obtained material as having slit pores or constructed from plane-parallel particles.

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