V. I. Solomonov

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 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.

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.

Feasibility of evaluating the quality of mined magnesite minerals using pulsed cathode luminescence

A new method for analyzing magnesite raw materials, namely, cathode luminescence, is discussed. The method is based on studying the luminescence excited by high-current nanosecond electron beams in the minerals (magnesite and admixtures). The possibilities of the method are shown for ten magnesite specimens. It is established that the luminescence parameters depend on the content of mineral admixtures in the magnesite, which makes it possible to recommend the method for estimating the quality of magnesite minerals.

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.

Luminescent Response to the Phase Composition of Nd3+:Y2O3-Al2O3 System

The work demonstrates the luminescent method of identifying the phase composition of Nd3+:Y2O3-Al2O3 system by building calibration curves using standard samples.

Determining the phase composition of yttrium oxide nanopowders by means of luminescence

The possibility of developing a luminescence technique for phase composition analysis is demonstrated via the example of bi-phase yttria nanopowders doped with neodymium ions. The deviation from X-ray diffraction reference values is ±2%. It is found that the results depend on the inhomogeneity of the crystalline phase distribution within a sample’s bulk, rather than on the luminescence scattering by powder nanoparticles. A luminescence coefficient that determines the phase inhomogeneity in nanopowders is introduced.