Lattice Site of Rare-Earth Ions in Stoichiometric Lithium Niobate Probed by OH− Vibrational Spectroscopy

Rare-earth (RE = Er3+, Nd3+, or Yb3+) ion-doped stoichiometric LiNbO3 crystals were grown by the Czochralski and the high-temperature top-seeded solution growth methods. For the 0.22–0.87 mol% concentration range of the RE oxides in the melt/solution, in addition to the well-known hydroxyl (OH−) vibrational band in undoped stoichiometric LiNbO3, a new infrared absorption band was observed at about 3500 cm−1, similar to the case of the trivalent optical damage resistant (ODR) dopants In3+ and Sc3+. By comparing the frequencies and polarization dependences of the bands to those detected for ODR ion containing crystals, they are attributed to the stretching vibration of OH− ions in RE3+Nb-OH− complexes. Consequently, above a given concentration threshold, some of the rare-earth ions are assumed to occupy niobium sites in the LiNbO3 lattice. The same model is also suggested for RE-doped congruent LiNbO3 crystals containing over-threshold (>5 mol %) amounts of the Mg-co-dopant

Identification of the binding site between bovine serum albumin and ultrasmall SiC fluorescent biomarkers

Ultrasmall silicon carbide nanoparticles (SiC USNPs) are very promising biomarkers for developing new applications in diagnostics, cell monitoring or drug delivery, even though their interaction with biological molecules such as different proteins has not yet been investigated in detail. In this study, the biological behaviour of SiC USNPs in a medium modeling a living organism was investigated in detail through the dependence of the fluorescence on interactions between bovine serum albumin (BSA) and SiC USNPs. The interaction shows transient nanoparticle–protein associations due to the restricted diffusion behaviour of the nanoparticles in the vicinity of a protein. The transient association manifests in a complex fluorescence quenching mechanism where the dynamic component was dominated by Fo¨rster resonance energy transfer. By studying SiC nanoparticles of different sizes, it can be concluded that the transient effect is an ultrasmall nanoparticle behaviour

Fázisegyensúlyok vizsgálata az X2O-Li2O-Nb2O5(X=Na, Rb, Cs) hármas rendszerekben, LiNbO3 egykristály növesztése és vizsgálata

The versatility of the application of LiNbO3 is well-known in the practical fields of acousto-electronics and non-linear optics and electro-optics. The optical damage threshold of stoichiometric LiNbO3 is higher so it is more suitable for electo-optical and non-linear optical applications than the congruent crystal which can be grown easier. The growth difficulties justify the development of alternative preparation methods or the improvement of the existing methods. This emphasizes the importance of the growth of stoichiometric LiNbO3 by the HTTSSG method not only from the K2O - Li2O - Nb2O5 ternary system but from the X2O - Li2O - Nb2O5 (X = Rb, Cs) systems as well. Using the presented phase diagrams the composition of the solution in equilibrium with a custom-tailored crystal composition can be determined. Most of the physical parameters of LiNbO3 are composition dependent. Even a small change of the composition (± 0.01 mol%) causes large differences in the properties so the determination of the Li2O content of the crystal with the highest possible accuracy is very important. The accuracy of the composition determination ? described in detail in my thesis ? based on the intensity ratio of the two characteristic bands in the OH- vibrational spectra of the near stoichiometric LiNbO3 satisfies the requirements imposed by the applicationsLa versatilité de LiNbO3 est bien connue dans le domaine de l?électronique acoustique (filtres SAW), de l?optique non linéaire et de l?optique électronique. Alors que les applications de LiNbO3 congruent sont répandues dans le domaine de l?électronique acoustique et de l?optique où les puissances ne sont pas très élevées, le seuil de dommage optique étant relativement bas, les applications sont limitées dans le domaine des fortes puissances lumineuses. Le seuil de dommage optique de LiNbO3 st?chiométrique est plus haut et rend nécessaire l?utilisation d?une méthode de croissance plus difficile (flux). Les difficultés de la méthode de croissance par flux justifie la recherche en vue de développer des méthodes alternatives ou d?améliorer les méthodes élaborées. Dans ma thèse j?ai présenté des solvants alternatifs á la croissance de monocristaux de LiNbO3 à partir du système ternaire K2O-Li2O-Nb2O5. J?ai prouvé qu?il est possible de faire croître des cristaux st?chiométriques par la méthode HTTSSG à partir des systèmes ternaires X2O-Li2O-Nb2O5 (X = Rb, Cs). Les diagrammes de phase tracés et précisés au cours de ce travail sont importants et donnent la possibilité de composer le flux à partir duquel il est possible d?obtenir le cristal de son choix. Comme pour les matériaux typiquement non st?chiométrique, les paramètres physiques de LiNbO3 sont très sensibles aux moindres variations de la composition (± 0.01 mol%). La détermination précise de la composition est donc très importante. Dans ma thèse, j?ai élaboré une nouvelle méthode de haute précision basée sur le rapport des deux principaux pics vibrationnels OH- dans l?infrarouge. Cette méthode a une précision qui satisfait les exigences de qualification des cristaux de LiNbO

Etude des équilibres entre phases dans les systèmes ternaires X2O-Li2O-Nb2O5 (X=Na, Rb, Cs), croissance cristalline et caractérisation de LiNbO3

La versatilité de LiNbO3 est bien connue dans le domaine de l électronique acoustique (filtres SAW), de l optique non linéaire et de l optique électronique. Alors que les applications de LiNbO3 congruent sont répandues dans le domaine de l électronique acoustique et de l optique où les puissances ne sont pas très élevées, le seuil de dommage optique étant relativement bas, les applications sont limitées dans le domaine des fortes puissances lumineuses. Le seuil de dommage optique de LiNbO3 stœchiométrique est plus haut et rend nécessaire l utilisation d une méthode de croissance plus difficile (flux). Les difficultés de la méthode de croissance par flux justifie la recherche en vue de développer des méthodes alternatives ou d améliorer les méthodes élaborées. Dans ma thèse j ai présenté des solvants alternatifs á la croissance de monocristaux de LiNbO3 à partir du système ternaire K2O-Li2O-Nb2O5. J ai prouvé qu il est possible de faire croître des cristaux stœchiométriques par la méthode HTTSSG à partir des systèmes ternaires X2O-Li2O-Nb2O5 (X = Rb, Cs). Les diagrammes de phase tracés et précisés au cours de ce travail sont importants et donnent la possibilité de composer le flux à partir duquel il est possible d obtenir le cristal de son choix. Comme pour les matériaux typiquement non stœchiométrique, les paramètres physiques de LiNbO3 sont très sensibles aux moindres variations de la composition (+- 0.01 mol%). La détermination précise de la composition est donc très importante. Dans ma thèse, j ai élaboré une nouvelle méthode de haute précision basée sur le rapport des deux principaux pics vibrationnels OH- dans l infrarouge. Cette méthode a une précision qui satisfait les exigences de qualification des cristaux de LiNbO3The versatility of the application of LiNbO3 is well-known in the practical fields of acousto-electronics and non-linear optics and electro-optics. The optical damage threshold of stoichiometric LiNbO3 is higher so it is more suitable for electo-optical and non-linear optical applications than the congruent crystal which can be grown easier. The growth difficulties justify the development of alternative preparation methods or the improvement of the existing methods. This emphasizes the importance of the growth of stoichiometric LiNbO3 by the HTTSSG method not only from the K2O - Li2O - Nb2O5 ternary system but from the X2O - Li2O - Nb2O5 (X = Rb, Cs) systems as well. Using the presented phase diagrams the composition of the solution in equilibrium with a custom-tailored crystal composition can be determined. Most of the physical parameters of LiNbO3 are composition dependent. Even a small change of the composition (+- 0.01 mol%) causes large differences in the properties so the determination of the Li2O content of the crystal with the highest possible accuracy is very important. The accuracy of the composition determination described in detail in my thesis based on the intensity ratio of the two characteristic bands in the OH- vibrational spectra of the near stoichiometric LiNbO3 satisfies the requirements imposed by the applicationsMETZ-SCD (574632105) / SudocSudocFranceF

Formation of LiNbO₃ Nanocrystals Using the Solvothermal Method

The optimization of the parameters of the solvothermal synthesis of lithium niobate (LiNbO3, LN) nanocrystals from Nb2O5 and LiOH was performed. The effects of polyol media, reaction time and Li excess of the starting reagents were investigated. According to the X-ray diffraction phase analysis, Li3NbO4 and Nb2O5 were also detected besides the LN phase in many samples depending on the ratio of the starting components and the reaction time. The best yield and the most homogeneous LN phase was prepared by using diethylene glycol medium with a Li/Nb ratio of 1.5 and a 72 h reaction time. The size and the shape of the LN particles were characterized by scanning electron microscopy. The particle size distribution was narrow and under 100 nm for all cases

INVESTIGATION OF NEW FLUXES FOR THE SINGLE-CRYSTAL GROWTH OF STOICHIOMETRIC LITHIUM NIOBATE Phase relations in the ternary system Cs2O–Li2O–Nb2O5

International audienceThermoanalytical and crystal growth investigations of the ternary system Cs2O–Li2O–Nb2O5 are presented in order to grow stoichiometric LiNbO3 (LN) crystals. Part of the phase diagram is determined and subsolidus phases are identified at room temperature by X-ray powder diffraction. Among the constituent phases, a new tetragonal cesium lithium niobate phase is assessed. From the Cs2O–Li2O–Nb2O5 system, good quality quasi-stoichiometric LN crystals can be grown