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

Abstract

Rare-earth (RE = Er 3+ , Nd 3+ , or Yb 3+ ) ion-doped stoichiometric LiNbO 3 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 LiNbO 3 , a new infrared absorption band was observed at about 3500 cm −1 , similar to the case of the trivalent optical damage resistant (ODR) dopants In 3+ and Sc 3+ . 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 RE 3+ Nb -OH − complexes. Consequently, above a given concentration threshold, some of the rare-earth ions are assumed to occupy niobium sites in the LiNbO 3 lattice. The same model is also suggested for RE-doped congruent LiNbO 3 crystals containing over-threshold (>5 mol %) amounts of the Mg-co-dopant.

Structural and Magnetic Behavior of Oxidized and Reduced Fe Doped LiNbO3 Powders

“…Effectively, LN can be labeled with any of the following: dielectric, uniaxial crystal, metallic oxide, ceramic, ferroelectric, pyroelectric, piezoelectric, photorefractive, photovoltaic, non-centrosymmetric non-linear medium and frequency converter, among others. The exacerbation/detriment of a property associated with each of these terms is to be tuned by proper control of point defects, either intrinsic or extrinsic [12][13][14][15]. Historically, this has been a major subject of interest for the scientific community involved in the study of LN.…”

“…Particularly important are the extrinsic point defects, such as ion-doped LN crystals, for which the intrinsic capabilities of the crystal might not only be improved but new ones could also arise [15]. That is the case with Co-doped LN (LiNbO 3 :Co) and Fe-doped LN (LiNbO 3 :Fe), for which the manifestation of ferromagnetism at room temperature has been previously reported [16][17][18].…”

Lithium Niobate Single Crystals and Powders Reviewed—Part II

“…The use of dopants not only entails a modification of the intrinsic capabilities of the crystal, but also new ones that could arise, as stated by Kovács et al [73]. Laser emission is the best example of such, accomplished when lanthanide trivalent rare-earth ions are the dopants: Pr, Tb, Er, Nd, Yb, Eu, Dy, Ho, Tm [73,74].…”

“…The use of dopants not only entails a modification of the intrinsic capabilities of the crystal, but also new ones that could arise, as stated by Kovács et al [73]. Laser emission is the best example of such, accomplished when lanthanide trivalent rare-earth ions are the dopants: Pr, Tb, Er, Nd, Yb, Eu, Dy, Ho, Tm [73,74]. These may also be photorefractive ions; for example, the development of two-color holographic recording by doping with Pr 3+ and Tb 3+ has been highlighted [10,75,76].…”

Determination of the Chemical Composition of Lithium Niobate Powders

“…Conceptually, this can be understood by recalling the intrinsic nature of LN to deviate from the stoichiometric point. Under regular circumstances, LN contains high amounts of intrinsic defects such as anti-site Nb ions (Nb Li ), which are compensated by their charge-compensating Li vacancies (V Li ) [3,46]. Such a substitution mechanism imposes fundamental changes on the electronic structure, inducing in this way, variations in the macroscopic dielectric tensor of LN [16].…”