Correlation between Infrared Absorption and Lithium Sublattice Disorder in Magnesium-Doped Lithium Niobate

Abstract

Lithium niobate is a ferro- and piezoelectric material with excellent optical properties and a wide variety of applications. The defect structures of congruent and Mg-doped crystals are still under intense discussion. In this work, undoped lithium niobate and magnesium-doped lithium niobate grown from congruent melt with the addition of 0 to 9 mol% MgO were investigated by infrared absorption, establishing the dependence of the absorbance on the Mg-doping level in two bands related to OH− stretching vibrations. The absorption band at 3485 cm−1 peaks at a MgO concentration in melt of 1 mol% and vanishes for MgO concentrations above the threshold level for optical damage suppression (4.8 mol%). A corresponding peak occurs in the minimum yield of the 7Li(p,α)4He reaction during ion channeling measurements, indicating a maximum of disorder in the Li sublattice. A possible explanation for this correlation is the attribution of this absorption band to ilmenite stacking fault sequences instead of isolated NbLi antisites in undoped and low-doped material. On the other hand, the OH− absorption band at 3535 cm−1 stays weak up to the MgO concentration threshold, and then increases, hinting to a defect related to the increase of vacancies due to the lack of charge compensation.

Structure and Luminescent Properties of Double‐Doped LiNbO3:Zn:Mg Crystals

“…), as well as several dopants simultaneously. [ 1,7–9 ] The introduction of two dopants into a crystal in a different concentration ratio is of practical interest, since the combination of dopants provides new possibilities of controlling the optical properties of crystals. [ 1,7,10–12 ]…”

“…), as well as several dopants simultaneously. [1,[7][8][9] The introduction of two dopants into a crystal in a different concentration ratio is of practical interest, since the combination of dopants provides new possibilities of controlling the optical properties of crystals. [1,7,[10][11][12] Doping LN crystals with such photorefractive additives as magnesium and zinc leads to a decrease in the value of the coercive field (up to 4.6 and 1.4 kV mm À1 in LiNbO 3 :Mg and LiNbO 3 :Zn crystals) and a significant increase in the optical resistance of crystals to laser radiation.…”