Luminescent Properties of Lanthanum Borates LaBO3:Eu and La(BO2)3:Eu Obtained by the Extraction-Pyrolytic Method

The structure, IR absorption, luminescence, and luminescence excitation spectra of La0.98-xLuxEu0.02BO3 orthoborates synthesized at 970oC were studied at 0≤ x≤0.98. An increase in x leads to a sequential change of the structural state of the orthoborates. At first, the compound has the aragonite structure. Then, it becomes two-phase and contains the aragonite and vaterite phases. With a further increase in x, the compounds have the vaterite structure, then the vaterite and calcite structure, and, finally, the calcite structure. Correspondence between the structure and spectral characteristics of these compounds was established. Luminescence spectra were investigated at different wavelengths of exciting light. This allowed obtaining information on the structure of a near-surface layer and the bulk of microcrystals of the investigated samples. It is shown that the vaterite phase arises in the bulk of microcrystals of samples that have the aragonite structure. Keywords: phosphors for LEDs, rare earth orthoborates, X-ray diffraction analysis, IR spectroscopy, luminescence spectra.

Section: Luminescence Spectramentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The evolution of the spectral and structural characteristics of La-=SUB=-0.98-x-=/SUB=-Lu-=SUB=-x-=/SUB=-Eu-=SUB=-0.02-=/SUB=-BO-=SUB=-3-=/SUB=- orthoborates

Кедров

et al. 2022

“…At the same time, orthoborates ReBO 3 (where Re -Tb, Eu, Gd, Y) have only one structural modificationvaterite [29,30,32]. Orthoborate LaBO 3 has two phase states: the lowtemperature orthorhombic phase aragonite (SG Pnam) and the high-temperature monoclinic phase (SG P2 1 /m), in which LaBO 3 passes at a temperature of 1488 • C [31][32][33][34][35]. Lutetium ion in the structures of calcite, vaterite and aragonite surrounded by six, eight and nine oxygen atoms, respectively.…”

Section: Introductionmentioning

confidence: 99%

Structural and spectral characteristics of La-=SUB=-0.99-x-=/SUB=-Tb-=SUB=-x-=/SUB=-Eu-=SUB=-0.01-=/SUB=-BO-=SUB=-3-=/SUB=- orthoborates and energy transfer from Tb-=SUP=-3+-=/SUP=- to Eu-=SUP=-3+-=/SUP=-

Шмурак

V.V.

A.P.

et al. 2022

The structure, infrared (IR) absorption spectra, luminescence spectra (SL), and luminescence excitation spectra (LES) of La0.99-xTbxEu0.01BO3 orthoborates synthesized at 970oC at 0≤ x≤ 0.99 were studied. An increase in x leads to the successive emergence of three structural states of these compounds. At 0≤ x≤0.2, orthoborates have an aragonite structure; then, at 0.2<x <0.89, they become two-phase and contain the aragonite and vaterite phases. At 0.89≤ x≤ 0.99, the compounds have a vaterite structure. A correspondence between the structure and spectral characteristics of these compounds was established. It is shown that in La0.99-xTbxEu0.01BO3 orthoborates, as well as in La0.99-xYxEu0.01BO3, the band with λex=369 nm (7F0->5D2) in the LES and the band in the wavelength range of 577-582 nm (5D0->7F0) in the SL of these compounds can serve as indicators of the structural state of the sample. In the SL of the samples containing the aragonite and vaterite phases, two bands corresponding to these structures were simultaneously observed for the first time. It was established that the luminescence of Eu3+ ions in La0.99-xTbxEu0.01BO3 orthoborates, which occurs when the sample is excited by light in the absorption bands of Tb3+ ions, is due to the transfer of the electron excitation energy from Tb3+ ions to Eu3+ ions. The efficiency of this process in La0.9Tb0.09Eu0.01BO3 samples with an aragonite structure is 86%. Keywords: rare earth orthoborates, crystal structure, X-ray diffraction analysis, IR spectroscopy, luminescence spectra, phosphors for LEDs.

“…The LaBO 3 compound has two phase states: the low-temperature orthorhombic aragonite phase (space group Pnma) and the high-temperature monoclinic phase (space group P2 1 /m), to which LaBO 3 changes over at 1488 • C [6,17]. La 3+ ions in the aragonite structure are surrounded by nine oxygen ions, while boron ions have a trigonal coordination by oxygen [18][19][20][21][22][23][24][25]. It should be noted that Lu 3+ ions in the calcite structure, e.g.…”

Section: Introductionmentioning

confidence: 99%

Structural and spectral characteristics of Pr-=SUB=-1-x-=/SUB=-Lu-=SUB=-x-=/SUB=-BO-=SUB=-3-=/SUB=- orthoborates

Шмурак

Кедров

Kiselev

et al. 2022

The structure, IR absorption and luminescence spectra of Pr0.99-xLuxEu0.01BO3 orthoborates synthesized at 970oC were studied at 0≤ x≤0.99. An increase in the concentration of lutetium leads to a sequential change of the structural state of the orthoborates. At first, the orthoborates are single-phase and have an aragonite structure (0≤ x≤0.1). Then, they become two-phase and contain the aragonite and vaterite phases (0.1<x<0.6). With a further increase in x (0.6<x≤0.8), the compounds are single-phase with a vaterite structure, then they contain the vaterite and calcite phases (0.8<x≤0.95), and, finally, they become single-phase with a calcite structure (0.95<x≤0.99). An unambiguous correspondence between the structural modification and IR spectra of these compounds was established. It is shown that the emission of Eu3+ ions is observed in samples where the concentration of europium exceeds that of praseodymium. Keywords: rare earth orthoborates, X-ray diffraction analysis, crystal structure, IR spectroscopy, luminescence spectra.