Luminescent metal hydrides containing europium(II) and hydrogenation studies of ytterbium and LixSr1-1AlSi

The first systematic study of Eu(II)-luminescence in hydride and hydride-fluoride host lattices is described within the present work. Due to its high emission intensities and the dependence of its emission wavelength on its coordination sphere, Eu(II) is of major importance for the design of luminescent materials. Eu(II) luminescence was studied in hydrides of the alkaline earth metals MH2 (M = Ca, Sr, Ba), the perovskites LiMH3 (M = Sr, Ba), AMgH3 (A = Na, K), ternary magnesium hydrides and the hydride-fluorides EuHxF2-x, LiMHxF3-x (M = Sr, Ba) and KMgHxF3-x. Samples showed broad band emission as it is typical for the electric dipole transition 4f7 - 4f65d. The widest redshift ever observed in the emission of Eu(II) was found for the alkaline earth metal hydrides MH2 (M = Ca, Sr, Ba) and NaMgH3. Extremely well-resolved spectra of Eu(II) in LiSrD3 and LiSrH3 allowed the assignment of different vibrational modes and thus the clarification that the bonding in the 4fn-1 5d(eg) excited state is weaker than in the ground state and also the first quantitative estimation of the crystal field strength of hydride and deuteride ever. It was also shown that the variation of the hydride and fluoride content in mixed compounds allows the targeted design of phosphors with varying emission colors. Additionally, in-situ deuteration studies of Yb and theoretical studies of the hydrogenation of LixSr1-xAlSi were carried through.In der vorliegenden Arbeit wurde die erste systematische Untersuchung von Eu(II)-Lumineszenz in Hydrid- und Hydridfluoridwirtsgittern durchgeführt. Aufgrund seiner hohen Emissionsintensitäten und der Abhängigkeit der Emissionsenergie von der Koordinationssphäre ist Eu(II) von großer Bedeutung bei der Herstellung von Leuchtstoffen. Eu(II)-Lumineszenz wurde in den Hydriden der Erdalkalimetalle MH2 (M = Ca, Sr, Ba), den Perowskiten LiMH3 (M = Sr, Ba), AMgH3 (A = Na, K) und ternären Magnesiumhydriden sowie den Hydridfluoriden EuHxF2-x, LiMHxF3-x (M = Sr, Ba) und KMgHxF3-x untersucht. Die Verbindungen wiesen die für den elektrischen Dipolübergang 4f7 - 4f65d typischen breiten Emissionsbanden auf. Die weiteste bekannte Rotverschiebung der Emission von Eu(II) wurde für die Erdalkalimetallhydride MH2 (M = Ca, Sr, Ba) sowie NaMgH3 beobachtet. Hochaufgelöste Eu(II)-Spektren in LiSrD3 and LiSrH3 erlaubten die Zuordnung verschiedener Schwingungsmoden und somit die Klarstellung, dass die Bindungsstärke im angeregten 4fn-1 5d(eg) schwächer als im Grundzustand ist und weiterhin die erste quantitative Abschätzung der Kristallfeldstärke von Hydrid und Deuterid. Zusätzlich konnte gezeigt werden, dass die Variation von Hydrid- und Fluoridgehalt in gemischten Verbindungen die gezielte Synthese von Leuchtstoffen mit gewünschten Emissionsfarben ermöglicht. Zusätzlich wurden in-situ Deuterierungsuntersuchungen an Yb und theoretische Studien der Hydrierungen von LixSr1-xAlSi durchgeführt

Dephasing mechanisms of optical transitions in rare-earth-doped transparent ceramics

We identify and analyze dephasing mechanisms that broaden the optical transitions of rare-earth ions in randomly oriented transparent ceramics. The study examines the narrow F_0^7 ↔ D_0^5 transition of Eu^(3+) dopants in a series of Y_2O_3 ceramic samples prepared under varying conditions. We characterize the temperature and magnetic field dependence of the homogeneous linewidth, as well as long-term spectral diffusion on time scales up to 1 s. The results highlight significant differences between samples with differing thermal treatments and Zr^(4+) additive concentrations. In particular, several distinct magnetic interactions from defect centers are observed, which are clearly distinguished from the broadening due to interactions with two-level systems and phonons. By minimizing the broadening due to the different defect centers, linewidths of the order of 4 kHz are achieved for all samples. The linewidths are limited by temperature-dependent interactions and by an interaction that is yet to be identified. Although the homogeneous linewidth can be narrowed further in these ceramic samples, the broadening is now comparable to the linewidths achieved in rare-earth-ion–doped single crystals. Thus, this work emphasizes the usefulness of studying ceramics to gain insights into dephasing mechanisms relevant to single crystals and suggests that ceramics may be an interesting alternative for applications in classical and quantum information processing

Rare-earth doped transparent ceramics for spectral filtering and quantum information processing

Homogeneous linewidths below 10 kHz are reported for the first time in high-quality Eu3+ doped Y 2O3 transparent ceramics. This result is obtained on the 7F0→5D0 transition in Eu3+ doped Y 2O3 ceramics and corresponds to an improvement of nearly one order of magnitude compared to previously reported values in transparent ceramics. Furthermore, we observed spectral hole lifetimes of ∼15 min that are long enough to enable efficient optical pumping of the nuclear hyperfine levels. Additionally, different Eu3+ concentrations (up to 1.0%) were studied, resulting in an increase of up to a factor of three in the peak absorption coefficient. These results suggest that transparent ceramics can be useful in applications where narrow and deep spectral holes can be burned into highly absorbing lines, such as quantum information processing and spectral filteringThis work was supported by the ANR projects RAMACO (No. 12-BS08-0015-01) and DISCRYS (No. 14-CE26-0037-01), Idex No. ANR-10-IDEX-0001-02 PSL⋆, and Nano’K project RECTUS. C.W.T. and R.L.C. acknowledge support from National Science Foundation (NSF) Award Nos. CHE-1416454 and PHY-1415628 and M.O.R. and L.E.B. from Project No. MAT2013- 43301-R of the Spanish Ministry of Economy and Competitiveness (MINECO) and Comunidad Autónoma de Madrid under Grant No. S2013/MIT-274

High-Resolution Optical Line Width Measurements as a Material Characterization Tool

We present a case study on Eu^(3+)-doped Y_2O_3 transparent ceramics in which high-resolution laser spectroscopy is used as a material characterization tool. By comparing the results from coherent and incoherent optical spectroscopy with other characterization methods, we show that optical techniques can deliver supplementary information about the local environment of the activator ions in materials. Thus, high-resolution spectroscopy may be of interest for the investigation of a wider range of rare earth doped optical materials beyond materials studied for quantum information technology. The refinement of optical spectroscopy for the study of narrow optical transitions in rare earth ion single crystals has demonstrated that these techniques are extremely sensitive tools for probing the local environment of the rare earth ion. These techniques, such as photon echo experiments, have been important in developing materials for quantum information technology and spectral filtering applications. Here, we apply these techniques to transparent ceramic samples and compare the results with information gained from conventional material characterization techniques. Our present study demonstrates the high sensitivity of laser spectroscopic methods to microstructural strain and the presence of defects. In particular, the sensitivity is sufficient to detect small changes introduced by different thermal treatments in nominally equivalent materials. The results of our work show that it is possible to relate high-resolution optical measurements to defects and microstructural strain

Synthesis and crystal structure of the europium(II) hydride oxide iodide Eu5H2O2I4 showing blue-green luminescence

As the first europium(II) hydride oxide iodide, dark red single crystals of Eu5H2O2I4 could be synthesized from oxygen-contaminated mixtures of EuH2 and EuI2. Its orthorhombic crystal structure (a = 1636.97(9) pm, b = 1369.54(8) pm, c = 604.36(4) pm, Z = 4) was determined via single-crystal X-ray diffraction in the space group Cmcm. Anion-centred tetrahedra [HEu4]7+ and [OEu4]6+ serve as central building blocks interconnected via common edges to infinite ribbons parallel to the c axis. These ribbons consist of four trans-edge connected (Eu2+)4 tetrahedra as repetition unit, two H−-centred ones in the inner part, and two O2−-centred ones representing the outer sides. They are positively charged, according to ∞1{[Eu5H2O2]4+}, to become interconnected and charge-balanced by iodide anions. Upon excitation with UV light, the compound shows blue–green luminescence with the shortest Eu2+ emission wavelength ever observed for a hydride derivative, peaking at 463 nm. The magnetic susceptibility of Eu5H2O2I4 follows the Curie-Weiss law down to 100 K, and exhibits a ferromagnetic ordering transition at about 10 K

Dephasing mechanisms of optical transitions in rare-earth-doped transparent ceramics

We identify and analyze dephasing mechanisms that broaden the optical transitions of rare-earth ions in randomly oriented transparent ceramics. The study examines the narrow F_0^7 ↔ D_0^5 transition of Eu^(3+) dopants in a series of Y_2O_3 ceramic samples prepared under varying conditions. We characterize the temperature and magnetic field dependence of the homogeneous linewidth, as well as long-term spectral diffusion on time scales up to 1 s. The results highlight significant differences between samples with differing thermal treatments and Zr^(4+) additive concentrations. In particular, several distinct magnetic interactions from defect centers are observed, which are clearly distinguished from the broadening due to interactions with two-level systems and phonons. By minimizing the broadening due to the different defect centers, linewidths of the order of 4 kHz are achieved for all samples. The linewidths are limited by temperature-dependent interactions and by an interaction that is yet to be identified. Although the homogeneous linewidth can be narrowed further in these ceramic samples, the broadening is now comparable to the linewidths achieved in rare-earth-ion–doped single crystals. Thus, this work emphasizes the usefulness of studying ceramics to gain insights into dephasing mechanisms relevant to single crystals and suggests that ceramics may be an interesting alternative for applications in classical and quantum information processing

Lumineszierende Metallhydride mit Europium(II) und Hydrierungsstudien an Ytterbium und LixSr1-1AlSi

The first systematic study of Eu(II)-luminescence in hydride and hydride-fluoride host lattices is described within the present work. Due to its high emission intensities and the dependence of its emission wavelength on its coordination sphere, Eu(II) is of major importance for the design of luminescent materials. Eu(II) luminescence was studied in hydrides of the alkaline earth metals MH2 (M = Ca, Sr, Ba), the perovskites LiMH3 (M = Sr, Ba), AMgH3 (A = Na, K), ternary magnesium hydrides and the hydride-fluorides EuHxF2-x, LiMHxF3-x (M = Sr, Ba) and KMgHxF3-x. Samples showed broad band emission as it is typical for the electric dipole transition 4f7 - 4f65d. The widest redshift ever observed in the emission of Eu(II) was found for the alkaline earth metal hydrides MH2 (M = Ca, Sr, Ba) and NaMgH3. Extremely well-resolved spectra of Eu(II) in LiSrD3 and LiSrH3 allowed the assignment of different vibrational modes and thus the clarification that the bonding in the 4fn-1 5d(eg) excited state is weaker than in the ground state and also the first quantitative estimation of the crystal field strength of hydride and deuteride ever. It was also shown that the variation of the hydride and fluoride content in mixed compounds allows the targeted design of phosphors with varying emission colors. Additionally, in-situ deuteration studies of Yb and theoretical studies of the hydrogenation of LixSr1-xAlSi were carried through.In der vorliegenden Arbeit wurde die erste systematische Untersuchung von Eu(II)-Lumineszenz in Hydrid- und Hydridfluoridwirtsgittern durchgeführt. Aufgrund seiner hohen Emissionsintensitäten und der Abhängigkeit der Emissionsenergie von der Koordinationssphäre ist Eu(II) von großer Bedeutung bei der Herstellung von Leuchtstoffen. Eu(II)-Lumineszenz wurde in den Hydriden der Erdalkalimetalle MH2 (M = Ca, Sr, Ba), den Perowskiten LiMH3 (M = Sr, Ba), AMgH3 (A = Na, K) und ternären Magnesiumhydriden sowie den Hydridfluoriden EuHxF2-x, LiMHxF3-x (M = Sr, Ba) und KMgHxF3-x untersucht. Die Verbindungen wiesen die für den elektrischen Dipolübergang 4f7 - 4f65d typischen breiten Emissionsbanden auf. Die weiteste bekannte Rotverschiebung der Emission von Eu(II) wurde für die Erdalkalimetallhydride MH2 (M = Ca, Sr, Ba) sowie NaMgH3 beobachtet. Hochaufgelöste Eu(II)-Spektren in LiSrD3 and LiSrH3 erlaubten die Zuordnung verschiedener Schwingungsmoden und somit die Klarstellung, dass die Bindungsstärke im angeregten 4fn-1 5d(eg) schwächer als im Grundzustand ist und weiterhin die erste quantitative Abschätzung der Kristallfeldstärke von Hydrid und Deuterid. Zusätzlich konnte gezeigt werden, dass die Variation von Hydrid- und Fluoridgehalt in gemischten Verbindungen die gezielte Synthese von Leuchtstoffen mit gewünschten Emissionsfarben ermöglicht. Zusätzlich wurden in-situ Deuterierungsuntersuchungen an Yb und theoretische Studien der Hydrierungen von LixSr1-xAlSi durchgeführt

Daten speichern im Kristallgitter

Die Quanteninformationstechnik ist ein lebendiges Thema in der Forschung an anorganischen Materialien, beispielsweise bei der Verschlüsselung für Datentransfer oder für den Traum vom Quantencomputer. Neben supraleitenden Qubits oder Defektzentren in Diamant eignen sich möglicherweise seltenerddotierte Materialien dafür