Adam Watras

Luminescence properties and determination of optimal RE3+ (Sm3+, Tb3+ and Dy3+) doping levels in the KYP2O7 host lattice obtained by combustion synthesis

The β-KYP2O7 powders doped with Sm3+, Tb3+ and Dy3+ were obtained using a one-step urea-assisted combustion method. Their structural properties were characterized by X-ray diffraction (XRD) whereas spectroscopic properties like excitation, emission and luminescence kinetics were investigated at room temperature. β-KYP2O7 doped with Sm3+ and Dy3+ showed concentration quenching above 2 mol% of dopants whereas Tb3+ containing materials could be doped with higher concentrations. The main mechanisms of concentration quenching were identified as dipole–dipole for Sm3+ and Dy3+. Both dopants due to the abundant energy levels are strongly prone to quenching due to the non-radiative CR process whose efficiency strongly increases with the concentration of optically active ions. In the case of Tb3+ emission from both 5D3 and 5D4 levels was recorded. The 5D3 level vastly depopulates due to the CR process upon increase of the Tb3+ content whereas the slight 5D4 emission remains stable up to 5 mol%.

One step urea assisted synthesis of polycrystalline Eu3+ doped KYP2O7 – luminescence and emission thermal quenching properties

KYP2O7 powders doped with Eu3+ were obtained for the first time by a one-step urea-assisted combustion method. Detailed structural properties were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and X-ray fluorescence (EDX). Spectroscopic properties like excitation, emission and luminescence kinetics were investigated in the temperature range of 30–550 °C. The KYP2O7 doped with Eu3+ phosphor has a broad and intense absorption band centered at 213 nm, an absolute quantum yield of up to 62% and a luminescence quenching temperature of T0.5 = 400 °C. The thermal behavior analysis of the luminescence shows that non-radiative internal losses are the main mechanism responsible for quenching of the luminescence.

Temperature induced emission quenching processes in Eu3+-doped La2CaB10O19

La2CaB10O19 powders doped with Eu3+ ions were synthesized using a citric route for the first time. The La2CaB10O19 powders doped with Eu3+ ions were synthesized using citric route for the first time. The crystal structure, morphology and chemical composition of the engineered compounds were characterized in details using X-ray diffraction (XRD), Raman spectroscopy, transmission and scanning electron microscopy (TEM and SAED) and X-ray fluorescence (EDX). The photoluminescence properties (emission, excitation, excited state dynamics) were evaluated in the temperature range 300–700 K. We have found that the thermal dependency of Eu3+ emission is quite complex in LCBO. Four different temperature zones were found as well as contribution of a second emitter at higher temperature. The thermal quenching mechanisms of Eu3+ luminescence in this host lattice are addressed.

Forgotten and Resurrected Chernovite-(Y): YAsO4 Doped with Eu3+ Ions as a Potential Nanosized Luminophore

In the present work, a precipitation method was employed to prepare nanosized YAsO4 doped with Eu3+ ions. The raw nanomaterials have been thermally treated in a temperature range between 500 and 900 °C for 3 h. The XRD analysis demonstrated that the powders were single-phase nanopowders with high crystallite dispersion. Our studies were focused on relating the luminescence properties of the Eu3+ dopant to the nanocrystallite (NC) size. The average NC size varied accordingly between 15 and 45 nm. We have found that the size effect is manifested mainly in the expansion of the cell volume and broadening of XRD peaks, as indicated by Rietveld analysis. Moreover, the emission and excitation spectra, although typical for Eu3+ ions, demonstrated some degree of variability with calcination temperatures and doping concentration. To explain these differences, a detailed analysis of luminescence spectra by the Judd-Ofelt theory has been performed.

Structural, Raman, FT-IR and optical properties of Rb3Y2(PO4)3 and Rb3La(PO4)2 doped with Eu3+ ions

Rb3Y2(PO4)3 and Rb3La(PO4)2, undoped and doped with Eu3+ ions, were synthesised either by the Pechini method or solid state reaction. They were characterised by thermoanalytical methods, X-ray diffraction, IR and Raman spectroscopy as well as optical techniques. It was stated that Pechini and solid state reaction methods give the compounds with the same structure. The structural data result in the P21/m space group with Z = 2 and a = 9.78 A, b = 5.76 A and c = 7.77 A cell parameters for Rb3La(PO4)2 and cubic symmetry I21/3 with a = 16.87 A and Z = 16 for Rb3Yb2(PO4)3. In Rb3La(PO4)2 the reversible β/α phase transition is observed in the 960–1070 °C temperature range. The lifetime of the 5D0 excited state measured at 77 K is about 4 and 2 ms for Rb3La(PO4)2 and Rb3Y2(PO4)3, respectively.