Enhancement of emission intensity of LaVO₄:RE³⁺ luminescent solar light absorbers

Abstract

The investigated La1–xRExVO4 (RE = Eu, Sm) solid solutions are characterized by intensive emission of the RE ions that is excited from the wide spectral range including UV region of intrinsic transitions in the vanadate host. We have carried out comparable analysis of characteristics of the La1–xRExVO4 compounds synthesized by three different methods: solid state reaction, co‐precipitation and sol‐gel synthesis. The investigation revealed differences in luminescence and excitation spectra of samples obtained by different methods. Spectra of the samples with lower activator concentrations have a more complicated character. They contain exceed number of lines that is caused by formation of two types of RE3+ emission centers. Spectral exhibitions of the second (“at surface”) type of centers are observed up to x = 0.05, 0.1 and 0.3 for samples synthesized by solid state, co‐precipitation and sol‐gel methods, respectively. The presence of the “at surface” type of centers leads to essential increasing of total intensity of emission. Differences in excitation spectra give us a possibility to suppose that enhancement of luminescence intensity is also due to expanded excitation range caused by “at surface” centers in UV region. Therefore, “at surface” centers satisfy better absorption of UV light. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Structure and Properties of Microcrystalline Cellulose "Ceramics-Like" Composites Incorporated with LaVO4:Sm Oxide Compound

“…transitions intensity in the case of composites differs from one corresponding to "free" La 0.7 Sm 0.3 VO 4 powder [20].…”

“…The possibility of such influence is explained, first of all, by the fact that Sm 3+ ion in the nanosized LaVO 4 :Sm particles can be located both in the volume and on the surface of particles [20]. The Sm 3+ ions "at surface" can be sensitive to the effects of the cellulose surface molecular groups.…”

“…It is easy to conclude that the additive narrow PL lines and lines in excitation spectra are related with Sm 3+ ions. In fact, the positions of these groups of lines, their shapes and distribution of their intensity coincide with absorption and emission lines of the Sm 3+ ions in various crystalline [20,[23][24][25], glass-like hosts [26,27], and liquids [28]. Therefore, we can state that the observed PL groups of lines are due to radiation transitions 4 G 5/2 → 6 H 9/2 , 6 H 7/2 , 6 H 5/2 from excited 4 G 5/2 level to the lowest levels of the ground 6 H state [29][30][31][32][33].…”

“…Before discussion of the MCC-LaVO 4 :Sm composites luminescence properties, it worth noting that detailed data and analysis of the luminescence properties both of starting cellulose and LaVO4:Sm oxides can be found in our previous works [16] and [20], respectively. The PL of the MCC-LaVO 4 :Sm composites was studied under excitations in the spectral range from UV (250 nm) to yellow light (570 nm) (Figs.…”

“…Each mixture was stirred in agate mortar until homogeneity (on the eye) was reached. Finally, each portion was divided into 3 parts and each of them was separately undergone to compression at high pressure near 1 [20]. Previously we have also found that La 1−x Sm x VO 4 luminescence is undergone to concentration quenching.…”