Nanooptics and photonics 

Crystal structure and luminescence properties of La1-xSmxVO4 sol-gel nanoparticles doped with hetero valence impurity
Chukova O.1,  Dorofieieva A.1,  Nedilko S.A.1,  Nedilko S.G.1, Voitenko T.1, Paszkowicz W.2,  Rahimi Mosafer H.2,  Androulidaki M.3, Stratakis E.3 
1 Taras Shevchenko National University of Kyiv, Volodymyrska Str., 64/13, Kyiv 01601, Ukraine. E-mail: chukova@univ.kiev.ua
2 Institute of Physics, Polish Academy of Sciences, al. Lotników, 32/46, 02-668, Warsaw, Poland 
3 Institute of Electronic Structure & Laser (IESL) of Foundation for Research & Technology Hellas (FORTH), Heraklion 711 10 Crete, Greece.

The vanadate nanoparticles are currently intensively investigated as perspective luminescent converters for WLED and solar cell applications. Recently, we have reported some results of synthesis and investigation of luminescence properties of the La1-xSmxVO4 nanoparticles. Adoption of characteristics of these nanoparticles to requirements of the noted applications needs some modification of their spectral properties. With this aim we have doped several rare-earth vanadate nanoparticles with hetero valence impurities and study effects of such substitutions on the obtained samples properties. In this contribution we described the results of the Ca2+ dopants effects on the La1-xSmxVO4 nanoparticles structural and luminescent characteristics. 
The Ca2+- doped La1-xSmxVO4 (0.05 ≤ x ≤ 0.2) nanoparticles were synthesized by sol-gel method from the La(NO3)3, Eu(NO3)3, NH4VO3, Ca(NO3)2 reagents. The phase composition and crystal lattice parameters were studied using a Bragg-Brentano setting with incident-beam Johansson monochromator and a strip detector. The made samples were of multiphase monoclinic and tetragonal structure. Content of the tetragonal LaVO4 phase increased with increase of Sm3+ content. Emission spectra of the samples were observed in the 550 – 700 nm spectral range. Excitation spectra consisted of the main band in 250 – 350 nm range with maxima at 320 nm and three groups of narrow and structured components in 350 – 520 nm range. Spectral positions of the long wavelength edge of the excitation spectra depends on Ca2+ impurities concentration that could be important for practical applications of the investigated compounds. 
This  work  has  received  funding  from  the Polish National Agency for Academic Exchange and Ministry of Education and Science of Ukraine under grant  agreement  No M/43-2020 and from the  Horizon Europe research  and innovation program under  grant  agreement  NFFA No 654360.