We present a cathodoluminescence study of the spatial distribution of Eu²⁺ and Eu³⁺ dopants in hydroxyapatite powders. The results demonstrate that the distribution of europium ions in the hydroxyapatite lattice depends on their valence state. Monochromatic cathodoluminescence images from prismatic powders show that although the Eu²⁺ is distributed homogeneously in the entire powder volume, the Eu³⁺ is present mainly at the powder edges. The luminescence spectrum of the Eu²⁺ ions displayed a wide and strong blue emission centered at 420 nm, while the luminescence spectrum of the Eu³⁺ ions displayed several orange-red emissions covering the range from 575 to 725 nm. These emissions correspond to transitions between levels 4f⁶5d¹-4f⁷ (⁸S_7/2) of the Eu²⁺ ions and ⁵D₀-⁷F_J levels of the Eu³⁺ ions. Micro Raman measurements reveal that europium doping generates two phonon signals with frequencies of 555 and 660 cm^–1, both of which have not been reported earlier. The powders were synthesized by the combustion synthesis method, maintaining constant the concentration of the europium salt used, and varying the pH of the precursor solutions to modify the concentration ratio of Eu²⁺ with respect to Eu³⁺. X-ray photoelectron spectroscopy measurements were used to determine values of 0.32 and 0.55 for the ratio Eu²⁺/Eu³⁺ in samples synthesized at pH values of 6 and 4, respectively. Thermal treatments of the samples, at 873 K in an oxygen atmosphere, resulted in a strong quenching of the Eu²⁺ luminescence due to oxidation of the Eu²⁺ ions into Eu³⁺, as well as probable elimination of calcium vacancy defects by annealing.

We report a cathodoluminescence (CL) study of β-Ga₂O₃ nanowires grown by thermal evaporation of GaN on Si(100) and Au/Si(00) substrates. Condensation and subsequent oxidation of metallic Ga is suggested as the growth mechanism of β-Ga₂O₃ nanowires. The β-Ga₂O₃ nanowires grown on Si(100) show multiple bends or undulations, together with a strong UV emission at 3.31 eV and a weak blue emission centered at 2.8 eV as a band component. The β-Ga₂O₃ nanowires grown on Au/Si(100) substrates recorded a lower CL intensity of a well-defined blue emission of 2.8 eV. A thermal treatment on these samples produced an increase of the UV emission and quenching of the blue band. Thermal annealing of oxygen vacancies is proposed as the responsible mechanism for the observed behavior of these samples.

Implementation of more refined structures at the nano to microscale is expected to advance applications in optics and photonics. This work presents the additive manufacturing of 3D luminescent microarchitectures emitting light in the visible range. A tailor‐made organo‐metallic resin suitable for two‐photon lithography is developed, which upon thermal treatment in an oxygen‐rich atmosphere allows the creation of silicon‐free tetragonal (t‐) and monoclinic (m‐) ZrO₂. The approach is unique because the tailor‐made Zr‐resin is different from what is achieved in other reported approaches based on sol−gel resins. The Zr‐resin is compatible with the Eu‐rich dopant, a luminescent activator, which enables to tune the optical properties of the ZrO₂ structures upon annealing. The emission characteristics of the Eu‐doped ZrO₂ microstructures are investigated in detail with cathodoluminescence and compared with the intrinsic optical properties of the ZrO₂. The hosted Eu has an orange−red emission showcased using fluorescence microscopy. The presented structuring technology provides a new platform for the future development of 3D luminescent devices.