Investigations of the OH ⁻ absorption bands in congruent and near-stoichiometric LiNbO ₃ :Hf crystals

Abstract

PACS 61.72.-y -Defects and impurities in crystals; microstructure PACS 77.84.Ek -Niobates and tantalates PACS 78.30.-j -Infrared and Raman spectra Abstract -OH − absorption bands of both congruent and near-stoichiometric LiNbO3:Hf crystals were investigated. The abrupt blueshift of OH − absorption bands was found between the doping levels of 2 and 2.5 mol% in the congruent crystals, which confirms the exact optical-damage threshold for Hf doping. The absorption difference of OH − bands between the congruent and near-stoichiometric crystals shows that after Li incorporation H + ions no longer prefer the sites of 3500 cm −1 . Moreover, with the increase of Hf doping in the near-stoichiometric crystals, H + ions were found to gradually transfer to the sites of 3489 cm −1 . These results are explained by the breakdown of the association of Hf − Nb and H + ions and the subsequent redistribution of H + ions around Hf 3+Li ions in V − Li -deficient lattice. Additionally, the link between the intrinsic defects and how they influence the optical-damage threshold upon adding Hf was discussed in detail.

Photorefractive Properties of Molybdenum and Hafnium Co-Doped LiNbO3 Crystals

“…On the basis of previous work, the optimal results were obtained when the doping concentration of Mo 6+ was 0.5 mol %, and for Hf 4+ the doping threshold is between 2.0 and 2.5 mol % [17,23]. Therefore, we fixed the concentration of Mo 6+ at 0.5 mol % and selected the Hf 4+ concentrations of 0.0, 2.0, and 3.5 mol %, which are labeled as LN: Mo, LN: Mo, Hf 2.0 , and LN: Mo, Hf 3.5 , respectively.…”

“…The OH − absorption peak of the CLN crystal is about 3484 cm −1 , so for comparison we only took values between 3420 cm −1 and 3560 cm −1 and then normalized them. Based on previous reports, the shift of Hf-doped LiNbO 3 crystals is very slight [23], and it is necessary to study the internal structure of the OH − absorption peak in more detail. The OH − absorption band of CLN crystal is broad, and we can decompose it into three peaks, in which the peak of 3466 cm −1 is thought to be caused by the direct substitution of protons for Li + ions, while the 3481 and 3489 cm −1 peaks are due to protons occupying the Li vacancy (V Li − ) in two different ion environments near Nb Li 4+ [25].…”

Hf 4+ Ion Concentration Dependence of Holographic Storage Properties in Hf:Fe:Cu:LiNbO3 Crystals

“…Recently, being a favorable material for holographic storage application, co‐doped Fe:Cu:LiNbO 3 crystal has attracted extensive interest . However, it also has shortcomings, such as optical damage, longer response time, and lower sensitivity . In order to eliminate the defect of the co‐doped crystals, people dope rare‐earth ions into the crystals .…”