A. V. Spirina

Raman scattering and luminescence of yttria nanopowders and ceramics

We have studied Raman scattering in yttria nanopowders and ceramics that was excited by radiation at wavelengths of 514.5 and 632.8 nm. We show that, in undoped nanopowders and cubic phase of doped yttria ceramics, only the Raman scattering by phonons is observed, with no other Raman scattering centers having been revealed. In nanopowders of the monoclinic phase, we have observed an additional Raman line with a Raman shift of 1093 ± 4 cm−1. If all the objects under investigation are excited by the radiation at a wavelength of 514.5 nm, their spectra exhibit four series of photoluminescence lines, two of which (at λ = 521–523 and 538–564 nm) are emitted by Er3+ ions, “impurity” dopants, while the other two lines (at λ = 607–635 and 644–684 nm) are emitted by intrinsic centers. Under excitation by the radiation at a wavelength of 632.8 nm, only a series of bands at λ = 644–684 nm is emitted. In addition to these photoluminescence bands, neodymium-doped ceramics show photoluminescence bands of Nd3+ ions. We have shown that intrinsic luminescence centers, which occur in all the examined specimens, are capable of acting as acceptors with respect to neodymium ions excited to the upper laser level.

Trivalent zirconium and hafnium ions in yttrium oxide ceramics

An analysis of the electron spin resonance (ESR) spectrum of transparent ceramics composed of yttrium oxide with zirconium and hafnium additives has revealed the presence of signals (with similar parameters) from Zr3+ and Hf3+ ions, which have a similar electron configurations of the ground states: [Kr]4d1 and [Xe]5d1, respectively. It is shown that the pulsed cathodoluminescence spectra of these ions consist of two bands peaking at λ ≈ 818 and 900 nm.

Luminescence study of neodymium-doped yttrium aluminates

This paper presents the results of a study of the pulsed cathodoluminescence of samples of neodymium-doped yttrium aluminates. It is found that the d–f emission bands of the Nd3+ ion dominate the spectrum of yttrium aluminum garnet in the visible region. The relative intensities and widths of the d–f bands vary as the crystal structure changes, and new luminescence bands appear. The luminescence bands of Nd3+ in the yttrium aluminum garnet and orthorhombic yttrium monoaluminate structures are identified. It is proposed to use two regions of the emission bands of Nd3+ in yttrium aluminum garnet as analytical bands to determine the concentration of the cubic phase: those at λ1=350–500 nm and λ2=501–650 nm.

Luminescence of neodymium-doped yttria

Pulsed cathodoluminescence of Nd3+: Y2O3 nanopowders of the cubic and monoclinic phases and the ceramics synthesized from these nanopowders has been investigated in the spectral range 350–850 nm. It is found that the IR emission band of neodymium ions in the Nd3+: Y2O3 cubic phase is located at λ1 ≈ 825 nm. When there is a monoclinic phase admixture, two additional luminescence bands of Nd3+ arise in the spectrum at λ2 ≈ 750 nm and λ3 ≈ 720 nm. The emission spectrum of all Nd3+: Y2O3 materials also contains a wide intrinsic band of yttrium oxide at λ ≈ 485 nm; however, the presence of neodymium decreases the intensity of this band and increases the its structurization. It is suggested that the structure of this band in Nd3+: Y2O3 materials is mainly determined by local absorption (self-absorption) of neodymium ions.

Luminescence and absorption of divalent ytterbium ion in yttrium-aluminum garnet ceramics

Strong absorption bands at 280, 385, and 640 nm; a pulsed cathodoluminescence band with peaks at 325 and 520 nm and a dip at 385 nm; and a structured luminescence band in the range of 591–711 nm composed of four pair lines and having a dip near 640 nm have been observed in the spectra of yttrium-aluminum garnet ceramics activated with ytterbium (10 mol %) and subjected to vacuum sintering at a temperature of 1800°C. It is shown that these spectral features are absorption and luminescence bands of divalent ytterbium ions with the 4f136s electron configuration of the ground state. These ions occupy the cubic site that is formed under conditions of oxygen deficit and disappears when the latter is removed during annealing ceramics in air.

Divalent ytterbium ions in yttrium aluminum garnet and yttrium oxide ceramics

Laser ceramics based on ytterbium-doped yttrium aluminum garnet and yttrium oxide are synthesized. The transmission, pulsed cathodoluminescence, and electron-spin resonance spectra of these ceramics at room temperature are measured and analyzed. It is shown that all the samples contain Yb2+ ions with the 4f136s electronic configuration of the ground state, which manifest themselves in the form of relatively weak bands in the IR region of the optical spectra in addition to the bands of Yb3+ ions.

Intrinsic luminescence centers in scandia, yttria, and their solid solutions

Pulsed cathodoluminescence (PCL) of Y2O3 and Sc2O3 powders, as well as of ceramic samples of binary (11 mol % Sc2O3–ZrO2 and 10 mol % Y2O3–ZrO2) and ternary (xSc2O3–(10–x)Y2O3–ZrO2) (x = 5, 6, 7, 8 mol %) solid solutions are studied in the range of 300–850 nm at room temperature. In Y2O3 and Sc2O3, series of strong narrow luminescence bands emitted by surface bound radicals ...0...0>-Y=O and ...0...0>-Sc=O are found. The PCL spectra of xSc2O3–(10–x)Y2O3–ZrO2 ceramic samples showed the same series of narrow bands at 543, 551, 555, 572, 583, 594, 614, and 639 nm as the yttrium oxide spectra. The existence of these luminescence bands, which correspond to the emission of the ...0...0>-Y=O radical, and the absence of the emission lines of the ...0...0>-Sc=O radical indicate that yttrium ions, due to their larger radius, are the first that are displaced to the surface of crystallites in these systems, which is accompanied by the formation of the second phase in subsurface layers.

The energy structure of a neodymium ion in monoclinic yttria

We present an energy level diagram of a Nd3+ ion in monoclinic γ-phase of yttria reconstructed from transmission spectra of Y2O3:Nd3+ nanopowders.

Luminescence of oxygen molecular ion in neodymium-doped yttria

Pulsed cathodoluminescence spectra of Nd3+:Y2O3 compacts registered after their annealing in air at a temperature above 950°C exhibit a structured band in the range 610–660 nm with four well-resolved components located at wavelengths of 620.6, 630.6, 645.3, and 655.6 nm. At the same time, the lattice parameter of the cubic yttria increases, and the color of samples changes from light blue to yellowish. In addition, the nearly complete absorption of the intrinsic luminescence band of yttria is observed in the range of 380–600 nm with a center at λ = 485 nm. We assume that these effects are caused by oxygen molecular ions O2−, which are formed in cubic yttria due to the penetration of oxygen into natural anion vacancies. The frequencies of vibrations of the ground and excited states of the oxygen molecular ion has been determined.

Spectroscopy of a laser plume arising under radiation of a ytterbium fiber laser

The spectra of luminescence of plumes that occur near targets of Nd: Y2O3, YSZ, and Al2O3 when they are irradiated by pulses of a ytterbium fiber laser with a wavelength of 1.07 μm, duration of 1450 μs, and intensity of 0.4 MW/cm2 are studied. Craters with a diameter of 400 μm and a depth of 600 μm appeared under such exposure in the targets. It is shown that the bands of the cation’s radicals of the targets, the intensities of which are distributed according to a law close to Planck’s law, predominate in the spectra of the plumes. On this basis, the temperature of the plumes was determined. It was about 2200–2280 K at the surface of the target, which is below the boiling temperature of the target due to cooling of the vapor during the passage of the deep laser crater.