Photo- and cathodoluminescence of cubic boron nitride micropowders activated by Tm, Tb, and Eu rare-earth ions

This work is devoted to the production of cubic boron nitride ($c$-BN) micropowders that are activated by ions of rare-earth elements, such as europium (Eu), terbium (Tb), and thulium (Tm), as well as to the study of the structural properties and photo- and cathodoluminescence of these micropowders. The micropowders have been synthesized from a hexagonal boron nitride powder in the presence of a catalyst under pressures of 4–6 GPa at temperatures of 1800–1900 K. The activation of the micropowders by the rareearth elements (REEs) has been carried out by introducing the corresponding REE compounds into synthesis precursor. The efficiency of the introduction of an impurity into the $c$-BN lattice is ~5%. The composition and structure of the samples have been examined using X-ray diffraction analysis, scanning electron microscopy, and energy-dispersive spectrometry. The results obtained during studying $c$-BN, $c$-BN:Tm, $c$-BN:Tb, and $c$-BN:Eu micropowders using color cathodoluminescence clearly demonstrate their ability to emit light in the wide spectral range, which is of interest for developing new light-emitting devices that are intended for operation in corrosive ambient. An analysis of the photoluminescence spectra of $c$-BN:REE micropowders has made it possible to find that the observed spectral bands belong to the corresponding transitions between the energy levels of the REEs, as well as to determine the probable positions of Tb$^{3+}$ and Eu$^{3+}$ ions in the cubic boron nitride lattice.