Comparable Structural and Luminescent Characterization of the La_1-xEu_xVO₄ Solid Solutions Synthesized by Solid State and Co-Precipitation Methods

Abstract

Luminescence properties of the two series of the La1-xEuxVO4 (x ranges from to 0.3) solid solutions synthesized by the solid state and co-precipitation methods were investigated.. Luminescence spectra of the investigated samples consist of narrow spectral lines caused by inner f - f electron transitions in the impurity Eu3+ ions. Excitation spectra consist of three main bands those correspond to different types of transitions in the investigated matrices. There are O - Eu3+ charge transfer transitions, band-to-band transitions in the matrix of the vanadate compounds and electron transitions in the VO43- vanadate anion. Dependences of the structure and luminescence properties on rate compositions and method of synthesis were studied. Origins of the observed differences between luminescence characteristics of the samples obtained by two different methods are discussed.

Synthesis and Properties of the La1 − x − y Eu y Ca x VO4 (0 ≤ x, y ≤ 0.2) Compounds

“…Excitation spectra of all the synthesized samples are typical for luminescence excitation spectra of undoped and doped with Eu 3+ ions LaVO 4 [20–23, 42–44]. They contain wide band with peak position at about 320 nm (Fig.…”

“…To confirm this supposition, we performed additive experimental study of the sample that does not contain Ca 2+ ions, namely, La 0.9 Eu 0.1 VO 4 composition of tetragonal structure [14, 23] (Figs. 6 and 7, curves 5).…”

Synthesis and Investigation of La,Ca ‐Doped EuVO4 Nanoparticles with Enhanced Excitation by Near Violet Light

“…The 380–425 and 460–480 nm bands correspond to range of the 5 F 0 → 7 D 3 and 5 F 0 → 7 D 2 excitation transitions in the Eu 3+ ions, respectively . The 320 nm band in vanadate compounds is usually connected with 1 A 1 → 1 T 2 transitions in the VO 4 3‐ anions . The additional wide excitation band near 370–390 nm is related with influence of the Ca 2+ impurities as this band was not observed nor for the EuVO 4 neither for the Ca‐free La 1− x Eu x VO 4 samples (Figure , curve 5,).…”

“…The 320 nm band in vanadate compounds is usually connected with 1 A 1 → 1 T 2 transitions in the VO 4 3‐ anions . The additional wide excitation band near 370–390 nm is related with influence of the Ca 2+ impurities as this band was not observed nor for the EuVO 4 neither for the Ca‐free La 1− x Eu x VO 4 samples (Figure , curve 5,). Origin of this band will be considered below when discussing emission spectra in their comparison with properties of the La 1− x − y Eu y Ca x VO 4 compounds.…”

“…The Ca 2+ cation, VO 4 3‐ anion and oxygen vacancy trapped electron [V O + e] + can form electro neutral complexes with strongly distorted symmetry of tetrahedral VO 4 3‐ groups. It is well known that excitation bands of vanadate compounds in the 270–350 nm spectral range are caused by 1 A 1 → 1 T 1 and 1 T 2 transitions in the VO 4 3− anions . Significant deformations of molecular orbitals of the VO 4 3− groups could influence their energy levels and increase probability of excitation transitions with participation of lower triplet states.…”