A study of the effect of annealing on Fe-doped LiNbO₃by HRXRD, XRT and FT–IR

Abstract

The annealing effect on the structural perfection of Fe-doped LiNbO 3 single crystals has been studied by high-resolution X-ray diffractometry (HRXRD), X-ray topography (XRT) and Fourier transform infrared (FT-IR) spectroscopy. The single crystals, prepared by mixing Li 2 CO 3 and Nb 2 O 5 powders in the molar ratio 48.6:51.4 with 0.05 mol% of iron at 1415 (1) K, were grown by the Czochralski (CZ) method along the [001] direction in air and poled during crystal growth by the application of a DC field. Two low-angle (tilt angle $1 arc minute) structural grain boundaries were observed in as-grown specimens. FT-IR spectra revealed that these crystals contain OH À and CO 3 2À ionic defects. Grain boundaries and CO 3 2À ionic defects were successfully removed, while the concentration of OH À ions was considerably reduced by post-growth thermal annealing at elevated temperatures.

Remarkable enhancement in crystalline perfection, second harmonic generation efficiency, optical transparency, and laser damage threshold in potassium dihydrogen phosphate crystals by L-threonine doping

“…3. The spectra ͑a͒, ͑b͒, ͑c͒, and ͑d͒, respectively, of pure, LT did not influence the internal vibrational modes of crystals as there is no shift or broadness of the main peak at 914 cm −1 corresponding to the asymmetric stretching vibration of H 2 PO 4 − anions at all concentrations. The same nature of all spectra confirms no deviation in tetragonal phase and also reveals the absence of any additional phase with LT doping at any concentration which is in tune with the powder XRD.…”

“…The curve is reasonably sharp having full width at half maximum ͑FWHM͒ of 7 arc sec as expected for a nearly perfect crystal from the plane wave dynamical theory of XRD. 30 Absence of additional peaks shows that the specimen crystal does not contain any internal structural grain boundaries 4 and indicates that the crystalline perfection is quite good.…”

“…Most of the anisotropic physical, optical, and electrical properties of the single crystals get deteriorated or completely diminished when these are not in the single domain crystal or having the defects like structural grain boundaries. 4,5 In parallel to the invention of new NLO materials, it is also important to modify the physical, optical, and electrical properties of these materials either by adding functional groups 6 or incorporation of dopants 7,8 for tailor made applications. In the presence of dopants growth promoting factors like growth rate 9 and many of the useful physical properties like optical transparency, 10,11 second harmonic generation ͑SHG͒ efficiency, 8 laser damage threshold ͑LDT͒, etc., get enhance.…”

Effect of necking on Czochralski-grown LiF crystals and its influence on crystalline perfection and the correlated physical properties

“…The solid red curve, which fits well with the experimental points (filled circles), was obtained by the convolution of the three peaks. Because of the good fit, it is clear that the two additional peaks correspond to two internal structural low-angle (tilt angle > 1 arcminute but less than a degree) grain boundaries (Bhagavannarayana, Ananthamurthy et al, 2005) whose tilt angles (misorientation angle between the two crystalline regions on each side of the structural grain boundary) are 648 and 412 00 from the main crystal block. The FWHM of the main peak and the very low angle boundaries are, respectively, 180, and 155 and 196 00 .…”

“…The moisture can be attacked in the title crystal at 673 K and it will soften at 873 K. In view of the above-mentioned potential applications of this material, it is important to grow defect-free bulk single crystals. Most of the anisotropic physical properties of single crystals, such as optical, electrical and dielectric properties, deteriorate or are significantly diminished when they are not in the single-crystal domain or have defects such as structural grain boundaries (Bhagavannarayana, Ananthamurthy et al, 2005;.…”