David John

Lanthanide-doped fluorides are promising materials for advanced photonic and quantum applications due to their wide bandgap, low phonon energy, and chemical stability. In this work, we investigate the influence of the host cation, Ba2+ versus Ca2+, on the charge state, local environment, and incorporation behavior of ytterbium (Yb) dopants in BaF2 and CaF2 single crystals at low doping levels (0.05–0.2 mol%). Using a combination of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), transmittance, and infrared photoluminescence (IR PL), we explore how host lattice properties affect the stabilization of Yb3+ and Yb2+ ions. XRD confirmed cubic phase purity and lattice parameter stability in both hosts, while XPS revealed surface chemical composition variations associated with charge-compensating defects and trace impurities. EPR spectra indicated that BaF2 favored perturbed Yb3+ environments with increasing dopant levels, while CaF2 maintained predominantly unperturbed sites, suggesting a more favorable ionic match for Yb2+. Photothermal deflection spectroscopy (PDS) and IR PL results showed host-specific optical responses, with CaF2 exhibiting crystal-field splitting and broader local field effects. These findings highlight the critical role of host cation identity in governing Yb charge state and lattice interaction, offering valuable insights for optimizing rare-earth-doped fluoride crystals in laser, scintillator, and quantum device applications.

Substituting Sc ³⁺ for Al ³⁺ in Pr ³⁺ -doped Lu _1.5 Y _1.5 Al _{5− x} Sc _x O ₁₂ crystals enhances the Pr ³⁺ emission across the UV-Vis-NIR spectral range. This enhancement is attributed to an efficient Sc ³⁺ → Pr ³⁺ energy transfer and increased structural disorder.

Radiocarbon dating is an established method that helps to determine the absolute age of archaeological finds. This topical review presents the basic principles of the radiocarbon method, conventions for selecting samples from archaeological contexts, how to handle samples before sending them to the radiocarbon laboratory, laboratory methods for sample preparation, the AMS measurement procedure, and the cali bration of results. Factors that limit the results of radiocarbon dating, particularly radiocarbon plateaux and the reservoir effect, are explained along with the ways how to recognise and eliminate their influence. The main aim of the paper is to critically evaluate the application of radiocarbon dating to less common archaeological samples (lipids preserved in the pores of pottery, charred bone, dental calculus, iron objects and iron slags, mortar, pollen and phytolith concentrates extracted from sediments or soils). Their dating opens new possibilities for the chronological determination of past natural and cultural processes or events. radiocarbon dating-lipids-charred bones-dental calculus-iron-mortar-pollen and phytolith con centrates

Conjugated BaI₂:Eu (5 at.%) nanocrystalline particles were synthesized, decorated with golden nanoparticles (GNP). GNP demonstrated some hydrophilic effect, leading to the BaI₂·H₂O phase creation. The Eu²⁺ luminescence intensity was reduced according to the GNP content. This was due to the decreased number of Eu²⁺ ions in the BaI₂, most probably, arising from the Au substitution for Ba competing with Eu. Moreover, the decay time of luminescence was decreased upon GNP content. This was explained by the moderation of negative charge in the GNP, leading to the repulsion with an electron in the excited Eu²⁺.