Slow-cooling Technique Research Articles

Divalent and trivalent neodymium photoluminescence in NaMgF3:Nd

Photoluminescence from Nd3+ and Nd2+ ions was observed in polycrystalline NaMgF3:Nd synthesised via a high-temperature melt, slow-cooling technique. The spectral features of Nd3+ were directly attributed to known intraconfigurational 4f3 → 4f3 transitions, where numerous emissions occurred in the infrared spectral region 840 nm–1390 nm. Additional emissions were observed over the range 850 nm–1500 nm that could not be attributed to Nd3+. The additional emissions were attributed to specific intraconfigurational 4f4 transitions of Nd2+ via comparison of the photoluminescence features with the known transitions of the isoelectronic Pm3+ ion in similar host compounds. The energies of the Nd2+ 4f4 levels were compressed by a factor of 1.09 relative to the Pm3+ ion. X-ray irradiation produced a radiophotoluminescence effect whereby the Nd2+ emission intensities increased for optical stimulations below 450 nm. Continuous stimulation at 400 nm reversed this effect. This phenomenon could be useful for applications in infrared lasing, radiation detection, and optical information storage.

Nucleation, growth, dielectric, polarizability, and Z-scan analysis of nicotinium tartrate & L-tartaric acid nicotinamide single crystals for third order NLO application: A comparative study

ABSTRACT Organic nonlinear optical (NLO) single crystalline materials of nicotinium tartrate (NT) and L-tartaric acid nicotinamide (LTN) were grown by slow evaporation solution technique (SEST), slow cooling technique (SCT), and seed rotation technique (SRT) using water as solvent. The growth of NT and LTN crystals by SCT and SRT are reported for the first time. Formation of nucleation from the supersaturated solutions of NT and LTN were observed experimentally using an optical microscope for different duration until the formation of nucleation with well-defined morphology for the first time. The dielectric constant and loss of the grown crystals were studied as a function of temperature by varying the frequency and vice versa and the results are discussed in detail. In addition, electronic properties such as plasma energy, Fermi energy, and electronic polarizability were calculated using Penn gap and Clausius-Mossotti relation and found that the polarizability values obtained are high in the present work. The low values of dielectric constant observed at high frequency regions indicate the suitability of these materials for nonlinear and electro-optical applications. The third order nonlinear optical parameters such as nonlinear refractive index (n2), nonlinear absorption coefficient (β), and third order susceptibility (χ3) were calculated using open aperture and closed aperture Z-scan techniques using He-Ne laser for the first time.

Investigations on nucleation, HRXRD, optical, piezoelectric, polarizability and Z-scan analysis of l–arginine maleate dihydrate single crystals

An efficient organic nonlinear optical single crystal of l-arginine maleate dihydrate (LAMD) has been grown by slow evaporation solution technique (SEST) and slow cooling technique (SCT). The crystalline perfection of the crystal was examined using high–resolution X–ray diffractometry (HRXRD) analysis. Photoluminescence study confirmed the optical properties and defects level in the crystal lattice. Electromechanical behaviour was observed using piezoelectric co-efficient (d33) analysis. The photoconductivity analysis confirmed the negative photoconducting nature of the material. The dielectric constant and loss were measured as a function of frequency with varying temperature and vice-versa. The laser damage threshold (LDT) measurement was carried out using Nd:YAG Laser with a wavelength of 1064 nm (Focal length is 35 cm) and the obtained results showed that LDT value of the crystal is high compared to KDP crystal. The high laser damage threshold of the grown crystal makes it a potential candidate for second and higher order nonlinear optical device application. The third order nonlinear optical parameters of LAMD crystal is determined by open-aperture and closed-aperture studies using Z-scan technique. The third order linear and nonlinear optical parameters such as the nonlinear refractive index (n2), two photon absorption coefficient (β), Real part (Reχ3) and imaginary part (Imχ3) of third-order nonlinear optical susceptibility are calculated.

Yb3+-doped KLu(WO4)2, Nb:RbTiOPO4 and KGd(PO3)4 crystals. Growth, characterization and laser operation

Macrodefect-free samples of Yb3+:KLu(WO4)2, Yb3+:Nb:RbTiOPO4 and Yb3+:KGd(PO3)4 laser crystals were grown using the Top Seeded Solution Growth – Slow Cooling technique. Structural and morphological studies related with the three materials were carried out and discussed. The dispersion of the refractive indices was measured and Sellmeier equations were constructed which are valid in the UV-Vis-IR range. The Stark splitting of the two electronic states of trivalent ytterbium was determined and the CW laser generation was demonstrated in these hosts. This paper shows a review of the main results achieved in FiCMA-FiCNA-URV laboratories in relation with these laser materials in the last years.

Crystal growth and optical characteristics of beryllium-free polyphosphate, KLa(PO3)4, a possible deep-ultraviolet nonlinear optical crystal.

Deep-ultraviolet nonlinear optical crystals are of great importance as key materials in generating coherent light with wavelength below 200 nm through cascaded frequency conversion of solid-state lasers. However, the solely usable crystal in practice, KBe2BO3F2 (KBBF), is still commercially unavailable because of the high toxicity of beryllium-containing and the extreme difficulty of crystal growth. Here, we report the crystal growth and characteristics of an beryllium-free polyphosphate, KLa(PO3)4. Centimeter-sized single crystals have been easily obtained by the flux method and slow-cooling technique. The second-harmonic generation efficiency of KLa(PO3)4 powder is 0.7 times that of KH2PO4; moreover, the KLa(PO3)4 crystal is phase-matchable. Remarkably, the KLa(PO3)4 crystal exhibits an absorption edge of 162 nm, which is the shortest among phase-matchable phosphates so far. These attributes make KLa(PO3)4 a possible deep-ultraviolet nonlinear optical crystal. An analysis of the dipole moments of the polyhedra and theoretical calculations by density functional theory were made to elucidate the structure-properties relationships of KLa(PO3)4.

Synthesis, growth and optical properties of an efficient nonlinear optical single crystal: L-alanine DL-malic acid

Single crystals of L-alanine DL-malic acid (LADLMA) have been grown from aqueous solution by slow-cooling technique. Powder X-ray diffraction studies reveal the structure of the crystal to be orthorhombic. The nonlinear optical conversion efficiency test was carried out for the grown crystals using the Kurtz powder technique. The third order nonlinear refractive index and the nonlinear absorption coefficient where evaluated by Z-scan measurements. As the material have a negative refractive index it could be used in the protection of optical sensors such as night vision devices.

Nanocrystalline Intermetallics in Al-Cu-Fe-Cr Decagonal Quasicrystalline Alloy

In the present investigation, an Al-Cu-Fe-Cr decagonal quasicrystalline alloy synthesized by a slow-cooling technique was mechanically milled in a high-energy ball mill for various times ranging up to 100 hours under liquid hexane medium at the speed of 400 rpm with a ball to powder ratio of 40:1. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential thermal analysis (DTA), and energy-dispersive x-ray analysis (EDX) were employed to characterize the as-cast, milled, and annealed samples. Powders milled for more than 10 h contained predominantly the B2-type nano-crystalline phase with a lattice parameter of ∼0.29 nm. The 100 h milled powder was annealed in air at 500°C for 20–40 h. It was observed that 40 h annealed sample shows the best yield for the fabrication of nanospinel. The processing technique could be optimized to manufacture the composites of nano-quasicrystal, nano-B2, and nanospinels. These materials may be further investigated as a suitable material for pigment industries.

Growth, Crystal Structure and Characterization of a New Single Crystal: Lithium Sodium Acid Phthalate (LiNaP), for Third Order Nonlinear Optical Applications

A new alkali metallo-organic single crystal of Lithium Sodium Acid Phthlate (LiNaP) complex has been synthesized from aqueous solution in the equimolar ratio 3:1:2. Transparent and bulk single crystals of dimension 9 × 4 ×2 mm3 have been grown from the conventional slow-cooling technique. The crystal structure of the compound has been solved from single crystal X-ray diffraction. The compound 2[C8H4O3]4-Li3+Na+ crystallizes in triclinic system with a space group of Pī having cell dimensions a = 7.5451(2) ? b = 9.8422(3) ? c = 25.2209(7) ? α = 80.299(2); β = 89.204(2); γ = 82.7770(10). FTIR measurement was carried out fo? LiNaP to study the vibrational structure of the compound. The various functional groups present in the molecule and the role of H-bonds in stabilizing the crystal structure of the compound have been explained. Optical absorption properties were studied for the grown crystal using UV-Vis-NIR spectrum. Thermal measurements were carried out for LiNaP to determine the thermal strength as well as to ascertain the hydrated nature of the crystal. Third order nonliner optical studies have also studied by Z-scan techniques. Nonlinear absorption and nonlinear refractive index were found out and the third order bulk susceptibility of compound was also estimated. The results of all studies have been discussed in detail.

Characterization of KNN Single Crystals by Slow-Cooling Technique

Lead free piezoelectric [001]-oriented (K 0.56 Na 0.44 )NbO 3 single crystals with very high crystallization have been grown by slow-cooling technique using 0.8(K 0.5 Na 0.5 )NbO 3 - 0.2K 2 CO 3 powder as starting materials. The dielectric properties, piezoelectric properties and domain structure of KNN single crystals were investigated. Three phase transition temperatures of rhombohedral-to-orthorhombic (R-to-O), orthorhombic-to-tetragonal (O-to-T) and tetragonal-to-cubic (T-to-C) are around −100°C, 214°C and 433°C for KNN single crystal according to the dielectric measurements, respectively. The relationship between dielectric permittivity ϵ and T(above T m ) is very well represented by a Cuire-Weiss law, where the Cuire constant C = 2.44 × 10 5 K and Curie-Weiss temperature T 0 = 647 K (374°C). The average piezoelectric coefficient d 33 of [001]-oriented KNN single crystal is 130pC/N at room temperature. The piezoelectric coefficient d 33 as a function of temperature was studied. The maximum d 33 reached to 220 pC/N around 130°C. Domain structure and the extinction of orthorhombic domain in [001]-oriented KNN single crystal was observed using polarizing light microscope.

Growth and characterization of pure and doped bis thiourea zinc acetate: Semiorganic nonlinear optical single crystals

Metal–organic coordination complex single crystals bis thiourea zinc acetate (BTZA) and Cd2+ doped BTZA have been synthesized and grown successfully by slow-cooling technique from their aqueous solutions. Single crystals of pure and Cd2+ doped BTZA with dimensions of 35×4×2mm3 and 10×5×6mm3, respectively were obtained with well defined morphology. The as grown single crystals are characterized by single crystal XRD studies and melting point measurements which reveal the incorporation of metallic dopants has not changed the structure of the parent crystal. The powder X-ray diffractogram of the grown crystals has been recorded and the various planes of reflection identified shows shift in the peak positions. The metal coordination with thiourea through sulphur in pure and Cd2+ doped BTZA were ascertained by FTIR studies and optical absorption study to identify the UV cut-off range. The presence of metals in pure and Cd2+ doped BTZA crystal lattice were confirmed by atomic absorption spectroscopy (AAS). The thermal decomposition of pure and Cd2+ doped BTZA crystals were investigated by thermo gravimetric analyses (TGA) and differential thermal analysis (DTA) indicate that doped crystals are more stable than pure crystals. The dielectric response of the crystals were studied in the frequency range 100Hz–5MHz at different temperatures and the results are discussed. Second harmonic generation (SHG) measurement confirms that the pure and Cd2+ doped BTZA have nonlinear optical (NLO) property. Laser damage threshold value of 12.44MW/cm2 has been determined using Q-switched Nd:YAG laser operating at 1064nm and with 8ns pulses in single shot mode for pure BTZA single crystal is reported for the first time.

Crystal growth and characterization of monometallic NLO single crystals of Cd(IO 3) 2

This work aims to study the growth and physicochemical properties of second-order nonlinear optical active inorganic crystal of cadmium iodate (CDI). Efforts have been made to grow an improved size single crystal of CDI by the slow-cooling technique. The XRD data of CDI are determined by single-crystal XRD analysis. CDI is further characterized by UV–vis–NIR spectroscopy, TGA, dielectric, ac conductivity, SEM and Vickers hardness studies. The second harmonic generation (SHG) of the sample is demonstrated by the Kurtz and Perry method using Nd:YAG laser and the results confirm that the grown crystal is roughly 6 times more efficient than KDP. The ac conductivity ( σ ac) of the grown crystal is measured in the frequency range 100 Hz–5 MHz and its temperature dependence is investigated. The estimated Vickers hardness number and work hardening coefficient of CDI ascertains the hard nature of the crystal.

Effect of different methods of cryopreservation on the cytoskeletal integrity of dromedary camel ( Camelus dromedarius) embryos

This study examined the effect of different methods of cryopreservation on the cytoskeletal integrity of camel embryos. A total of 32 embryos were recovered on Days 6 and 7 after ovulation and measured before being frozen using either a conventional slow-cooling technique ( n = 12: six Day 6 and six Day 7 embryos) or vitrification ( n = 12: four Day 6 and eight Day 7). The remaining 8 ‘control’ embryos (four Day 6 and four Day 7) were not cryopreserved but instead incubated in holding medium for 30 min. After thawing, warming or incubation, the embryos were stained with 4,6-diamino-2-phenylindole dihydrochloride (DAPI) to identify dead cells. Subsequently, the embryos were fixed in 4% paraformaldehyde, permeabilized and labelled with Alexa Fluor 488-Phalloidin to enable assessment of cytoskeleton integrity. Vitrified–warmed embryos contained a significantly higher percentage of dead cells than either conventionally frozen embryos or controls ( P < 0.05). Although the proportion of dead cells in conventionally frozen embryos tended to be higher than in controls, the difference was not significant ( P ≥ 0.07). Whereas embryo size did not affect the number of dead cells in conventionally frozen embryos, vitrified–warmed embryos >300 μm in diameter had a significantly higher percentage of dead cells than embryos ≤300 μm ( P = 0.01). Cytoskeleton integrity was also affected by both freezing method and embryo diameter. All 8 control embryos had a Grade I cytoskeleton, compared with only 2/24 (8.3%) frozen or vitrified embryos. Of the 8 slow-frozen or vitrified embryos with a Grade III cytoskeleton post-thaw, 7 had been vitrified and 6 were larger (Day 7) embryos. These results indicate that while both slow-freezing and vitrification of camel embryos lead to cytoskeleton disruption and cell death, embryo quality is better preserved by slow-freezing.

Growth and morphological aspects of Pb[(Sc 1/2 Nb 1/2) 0.58Ti 0.42]O 3 single crystals by slow-cooling technique

We report here the effect of growth parameters on the growth process of Pb[(Sc 1/2 Nb 1/2) 0.58Ti 0.42]O 3 (PSN–PT) single crystals in the flux method. PSN–PT single crystals have been grown by the slow-cooling technique using PbO+B 2O 3 flux. The size of the crystals varies from 1 to 4 mm, mostly showing regular cubic shape. Pure perovskite phase formation has been confirmed by X-ray diffraction technique. Rietveld analysis reveals that the grown crystals have the monoclinic structure in the Cm space group. This is consistent with the recent reports revealing monoclinic structure in relaxor-based ferroelectric single crystals. Scanning electron and optical microscopic studies have been used to analyze the surface morphology of the crystals and to predict the structural changes during growth. Dielectric measurement of (0 0 1) showed a dielectric maximum near 234 °C ( T c), which is higher than that of PZN–PT and PMN–PT.

Bulk Growth and Characterization of Semi-Organic Nonlinear Optical Bis Thiourea Bismuth Chloride Single Crystals

Growth and property studies of a new nonlinear optical (NLO) metal−organic crystal, bis thiourea bismuth chloride (BTBC), is reported. BTBC crystals were grown from aqueous solution by a slow-cooling technique. It has been observed that the solution pH influences the growth rate along the [001] and [010] directions. The grown crystals have been characterized for their structural, thermal, mechanical, linear, and NLO properties. BTBC is found to be a uniaxial and optically positive crystal. The birefringence value of BTBC is found to be 0.103. BTBC crystallizes in a hexagonal system, and the complex formation is stabilized by a metal−sulfur bond. BTBC has good optical transmission in the entire visible region and hence is a potential material for nonlinear frequency conversion.

Growth, spectroscopy and laser operation of Yb:KGd(PO3)4single crystals

Macrodefect-free single crystals of Yb-doped KGd(PO(3)), a noncentrosymmetric laser host which possesses second-order nonlinear susceptibility, were grown using the top seeded solution growth slow-cooling (TSSG-SC) technique, reaching a maximum ytterbium concentration in the crystal of approximately 3.2x10(20) at/cm(3). In order to evaluate the potential for self-frequency doubling, the dispersion of the refractive indices of KGd(PO(3))(4) was studied and Sellmeier equations were constructed which are valid in the visible and near-infrared. The Stark splitting of the two electronic states of ytterbium was determined from absorption and emission measurements at room and low temperatures, and this allowed to compute the emission cross sections at room temperature. The fluorescence decay time is quite long, 1.22+/-0.01 ms. Laser generation in the 1 mum range is demonstrated with this new Yb host for the first time. Although the maximum output power achieved, of the order of 100 mW, was limited by the available crystal size and doping level, the more than 55% slope efficiency obtained with this first sample is rather promising for the future.

Yb^3+ spectroscopy in (Nb or Ta):RbTiOPO_4 single crystals for laser applications

Single crystals of Yb:RbTiOPO(4) codoped with Nb(5+) or Ta(5+) were grown by the top seeded solution growth slow-cooling technique. The ytterbium concentration in the crystals varies as a function of the molar ratio of the precursor oxides and of the codopant, reaching a maximum value of 1.9x10(20) Yb(3+) ions/cm(3). The broad band near 1 mum in absorption and emission spectra at room temperature is due to the large splitting of the Yb(3+) ground state. The ytterbium (2)F(5/2) level radiative lifetime in Nb:RbTiOPO(4) (tau(rad) = 2.7 ms), was calculated and then compared to the measured fluorescence decay time (tau(em) = 2.2 ms), giving an intrinsic quantum efficiency of 81%. To evaluate the potentiality of these crystals for self-frequency doubling, preliminary results of Yb(3+) laser operation and fundamental wavelength measurements for type-II non-critical second harmonic generation ( lambda(NCPM)) are also reported.

Effect of sodium toluene sulfonate on the nucleation, growth and characterization of DAST single crystals

The metastable zone width and nucleation parameters such as interfacial tension were estimated for pure and sodium p-toluene sulfonate (NaTS)-doped 4- N, N dimethylamino-4′- N-methyl-stilbazolium tosylate (DAST) single crystals. Pure and additive-doped DAST single crystals were grown by the slow-cooling technique. The grown crystals were morphologically interpreted. The crystalline powders of the grown crystals were examined by X-ray diffraction to estimate the crystal lattice parameter values. From Vicker's microhardness test, the mechanical strength on (0 0 1) face of the crystals was found.

Growth and characterisation of EDTA-added TGS crystals

Triglycine sulfate (TGS) crystal with 1 wt% of EDTA (ETGS) addition was grown from aqueous solution by slow-cooling technique. The addition of EDTA enhanced the metastable zone width of TGS solution and, thereby, increased the growth rate of TGS crystal. The powder X-ray diffraction analysis showed a slight change in the cell parameter values of ETGS crystal. The presence of various functional groups in the grown crystal is identified from FTIR analysis. Optical transmission studies on ETGS crystal showed a lower UV cut-off of 237 nm and the transmission percentage of 95%. The dielectric studies were carried out to identify the phase transition temperature and to find the dielectric constant. The pyroelectric co-efficient was calculated, which increased slightly with EDTA addition in TGS. Piezoelectric studies were also done on the grown crystals. Microhardness studies carried out using Leitz–Weitzler hardness tester showed that the ETGS crystal was softer than pure TGS crystal.

Crystal Growth of RbTiOPO4:Nb: A New Nonlinear Optical Host for Rare Earth Doping

RbTiOPO4 doped with Nb (RTP:Nb) has been revealed as a new nonlinear optical host for rare earth doping. We have studied the growth conditions of single crystals of RTP:Nb doped with Er3+ and Yb3+ obtained by the TSSG (top-seeded-solution growth)/slow-cooling technique. The concentration of rare earth ions in RTP:Nb was 13 times higher than in RTP crystals. There were significant changes in the morphology of the crystals. While RTP crystals grew with normal morphology, showing the {100}, {201}, {201}, {110}, {011}, and {011} forms, RTP:Nb crystals show a habit as thin plates, maintaining all the forms above mentioned, but where the {100} form becomes the most developed in the crystal. RTP:Nb,Er and RTP:Nb,Yb crystals show the same habit as RTP:Nb crystals. A noncentric growth system, formed by a stirrer immersed in the growth solution, was used in the crystal growth process to minimize the difference in dimension between the a, b, and c directions in the crystals. We made preliminary optical characteriz...

Morphological aspects of flux grown 0.91PZN-0.09PT crystals

The nucleation and growth of 0.91PZN–0.09PT single crystals was investigated by the slow-cooling flux technique using PbO flux and by means of hot-stage microscopy. The results showed that during the initial stages of cooling small crystals of cubic morphology nucleated first. On further cooling, preferential growth developed along the four 〈111〉 corners of the cubic crystals, and one of the corners eventually outgrew the rest into a large arrowhead-shaped crystal against the heat flow direction. The terrace nature of the arrowhead crystals suggests that kinetic roughening, possibly promoted by a critical supersaturation in the solution, is the mechanism of the fast growth of PZN–PT crystals. The present work shows that under favorable conditions, such as with a high inverse temperature gradient and a solution cooling rate of about 1°C/h, large-sized PZN–PT crystals measuring 3.0×2.5×2.0cm3 can be reproducibly grown from PbO flux by the slow-cooling technique.