Pure KDP Research Articles

Growth and characterization of L‐alanine doped KDP crystals

AbstractPotassium Dihydrogen Phosphate (KDP) is an excellent inorganic nonlinear optical (NLO) material with different device applications. Most of amino acids possess NLO property; therefore, it is of interest to dope them in KDP crystals. In the present study, amino acid L‐alanine doped KDP crystals were grown by slow aqueous solvent evaporation technique. The doping of L‐alanine was confirmed by the paper chromatography, the CHN analysis and the FT‐IR spectroscopy. The powder XRD was carried out to assess the single phase nature of the samples. The effect of doping on thermal stability of the crystals was studied by TGA and the kinetic and thermodynamic parameters of dehydration were evaluated. As the amount of doping increased the thermal stability of crystals decreased. However, the second harmonic generation (SHG) efficiency and the UV‐Vis spectroscopy studies indicated that as the L‐alanine doping increased the SHG efficiency and optical transmission percentage increased. The dielectric behavior of the samples has been studied. The variation of dielectric constant, dielectric loss (tanδ), a.c.resistivity and a.c.conductivity with frequency of applied field in the range from 100 Hz to 100 kHz was studied. The dielectric constant and dielectric loss decreased with increase the value of frequency of applied field. The dielectric constant and the dielectric loss values of L‐alanine doped KDP crystals were lower than the pure KDP crystals. The results are discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Irradiation Effect on Second Harmonic Generation of Dyes Doped KDP Crystals

Most irradiation studies in the hydrogen bonded ferroelectrics have been concentrated on the transient defects induced by ionising radiation, such as ultraviolet (UV) light, where the defects are closely related to the optical properties. But heavy ion beam irradiation effects have rarely been studied. The structural, optical, and non-linear optical properties of the doped crystals were analyzed with the characterization studies, such as powder XRD, UV-Visible and second harmonic generation (SHG) measurements, respectively. The results for doped KDP crystal were compared with the results of the pure KDP crystals. The experiment results showed that Li3+ irradiation leads to the development of a well-defined surface H peak in dye doped KDP crystals. The stability of KDP single crystal was improved by doping organic dyes. The nano-islands of dye in KDP were likely to be dissolved and enhance the non-linear optical properties of these materials.

Structural, spectral, thermal, dielectric, mechanical and optical properties of urea l-alanine acetate single crystals

A new organic nonlinear optical crystal, urea l-alanine acetate (ULAA) has been grown by solution growth using slow cooling technique with the vision to improve the properties of the l-alanine crystals. Urea and l-alanine material were mixed in the molar ratio 1:4. Solubility and metastable zone width were determined. Single crystal XRD analyses revealed that the crystal lattice of ULAA is orthorhombic system, primitive lattice with cell parameters a=5.7971 Å, b=6.0391 Å, c=12.3276 Å with space group P2 12 12 1 (D 2 4). High-resolution X-ray diffraction (HR-XRD) analysis was carried out to study their crystalline perfection. FTIR spectrum was recorded to identify the presence of functional groups and molecular structure was confirmed by 1H NMR spectrum. From the mass spectrum, the ratio of compound formation of ULAA was analyzed. Thermal strength of the grown crystal has been studied using thermo-gravimetric (TG) and differential thermal analysis (DTA). Dielectric measurements reveal that the grown crystals have very low dielectric loss. The mechanical behavior was studied by Vickers microhardness test. The grown crystals were found to be transparent in the entire visible region. Preliminary measurement using Kurtz powder technique with Nd-YAG laser light of wavelength 1064 nm indicates that their second harmonic generation (SHG) efficiency is roughly equal to that of pure KDP.

FT-IR, Thermal and NLO Studies on Amino Acid (L-Arginine and L-Alanine) Doped KDP Crystals

Single crystals of pure and amino acid (L-arginine and L-alanine) doped potassium dihydrogen phosphate (KDP) for second harmonic generation have been grown from low temperature solution growth method by employing slow evaporation of the solvent. FT-IR spectrum of pure and doped KDP crystals confirms qualitatively the doping of the L-arginine and L-alanine in the host crystals. UV-visible spectroscopy shows the improvement in the transparency. Crystal structure has been studied by powder X-ray diffraction. Modification in the lattice parameters has been observed. Improvement in the SHG efficiency was studied by the Kurtz and Perry method. Thermal analysis has been performed on the grown crystals.

Analysis on suitability of pure and α-Histidine doped KDP crystals in high speed applications

Ferroelectric Potassium Dihydrogen Phosphate (KDP) crystals are widely used in modern short wavelength laser techniques, non-linear and integrated optics. The pure and α-Histidine doped KDP crystals were procured from SRM Institute of Science and Technology, Chennai. The presence of additive in the doped KDP crystal is confirmed through X-Ray diffraction patterns and the lattice parameters were evaluated. Also, Fourier Transform Infrared spectrum confirms the presence of α-Histidine in the doped crystals. The dielectric behaviour of the pure and doped crystals have been studied in the microwave region using K-band microwave bench equipped with the Gunn oscillator and guided with rectangular wave guide.

CRYSTAL GROWTH, THERMAL, OPTICAL, AND DIELECTRIC PROPERTIES OF L-LYSINE DOPED KDP CRYSTALS

Single crystals of pure and various amount of L-lysine doped KDP crystals were grown from aqueous solution. The doping of L-lysine was confirmed by CHN analysis and FT-IR spectroscopy. Powder XRD was carried out to assess the single phase nature of the samples. The effect of doping on thermal stability of the crystals was carried out by TGA and the kinetic and thermodynamic parameters of dehydration were evaluated. It was found that as the amount of doping of amino acid, L-lysine, increased the thermal stability of the grown crystals decreased. However, the second-harmonic generation (SHG) efficiency of Nd :YAG laser and UV-vis spectroscopy studies indicated that as the L-lysine doping increased in KDP crystals the SHG efficiency and optical transmission percentage increased. The dielectric constant and the dielectric loss of L-lysine doped KDP crystals are lower than the pure KDP crystals. Hence L-lysine doped KDP crystals are found to be more beneficial from an application point of view as compared to pure KDP crystals. The results are discussed.

Application of on-line Raman spectroscopy on monitoring semi-batch anti-solvent crystallization

Anti-solvent crystallization of potassium dihydrogen phosphate (KDP) from aqueous solution was studied by using on-line Raman spectroscopy. The used anti-solvent was acetone and semi-batch crystallization experiments were conducted by adding acetone into an initially pure aqueous KDP solution saturated at 25 °C. The solubility of KDP in acetone–water mixtures was determined at 25 °C. A calibration model of Raman spectra was created using a series of KDP–water–acetone ternary or binary solutions, and the calibration model was used to attain the on-line KDP concentration profile during the crystallization. The evolution of supersaturation during the whole process was then obtained. The reliability of the calibration model was validated by the off-line measured KDP concentrations. The effects of the feeding rate and feeding position of the anti-solvent on precipitation were discussed based on the obtained supersaturation profile.

Enhancement of stability of growth, structural and NLO properties of KDP crystals due to additive along with seed rotation

AbstractPotassium Acetate (CH3COOK) and Potassium Citrate (K3C6H5O7) as new additives were added into the potassium dihydrogen phosphate (KDP) solutions in different molar ratios. The metastable zone width and induction period with and without these additives were determined and compared. Dielectric measurements on pure and doped KDP crystals at various temperatures ranging from 313 to 423 K were carried out by the conventional parallel plate capacitor method which results low dielectric constant value dielectrics in doped crystals. The high resolution XRD studies show that CH3COOK doped KDP crystal and K3C6H5O7 doped KDP crystal do not contain any internal structural grain boundaries and indicates that the crystalline perfection is very good. Moreover, the addition of these potassium additives improves the quality of the crystal and yields highly transparent crystals with well defined features. The effect of additives on the growth, nucleation kinetics, structural, NLO and optical properties has been investigated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Growth and characterization of KDP crystals with potassium carbonate as additive

Potassium carbonate (K 2CO 3) as a new additive was added into the potassium dihydrogen phosphate (KDP) solutions in different molar ratios. The metastable zone width of KDP solution with 5 M% K 2CO 3 was determined and compared with the pure system. A good-quality KDP crystal with 5 M% K 2CO 3 additive was grown by the slow cooling method from aqueous solution by the rotation of the seed crystal with the in-house built rotation assembly. Dielectric measurements were carried out on pure and doped KDP crystals at various temperatures ranging from 313 to 423 K by the conventional parallel plate capacitor method, and it indicates that 5 M% K 2CO 3 addition leads to low dielectric constant value dielectrics. The addition of 5 M% K 2CO 3 and proper rotation of seed crystal (40 rpm) improves the quality of the crystal. The high-resolution X-ray diffractometry (HRXRD) analysis shows that the crystalline perfection of the crystal grown in these optimum conditions is extremely good without having any internal structural grain boundaries and mosaic nature. The crystals grown by these optimum conditions show positive effects in the various characterization techniques. The effect of additive on the growth, nucleation kinetics, structural, nonlinear optical, laser-induced damage threshold and optical properties have been investigated by the studies on pure and K 2CO 3-doped (in different concentrations viz., 1, 5 and 10 M%) KDP crystals grown under identical conditions.

Influence of lithium ions on the NLO properties of KDP single crystals

AbstractPotassium Dihydrogen Phosphate (KDP) and its isomorphous deuterated form are popular due to their applications in frequency converters and electro‐optic modulation. Different attempts have been made to dope KDP with inorganic additives, organic materials and amino acids. Since many of the metal ions possess more electro negativity which increases the non centrosymmetry, it is of interest to dope them in KDP. The influence of lithium ion (Li+) on NLO properties of KDP crystal has been studied in the present investigation. Single crystal of Lithium ion doped Potassium Dihydrogen Phosphate (KDP) was grown by slow evaporation technique. The enhancement in SHG efficiency after addition of ion Lithium (Li+) was observed by Kurtz Powder SHG test. It was found that the SHG efficiency of KDP after addition of Lithium ion is 1.33 times more than pure KDP. The crystal structure and cell parameters of grown crystal were determined by X‐ray diffraction. The Energy Dispersive X‐ray analysis (EDAX) gives the chemical composition of grown crystal. The functional groups were identified by FT‐IR spectral analysis. The presence of Lithium in the material of grown crystal was detected by Atomic absorption spectroscopy (AAS). The optical absorption and transmission studies were done by UV‐Visible spectral analysis. The grown crystal was subjected to thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Nucleation studies and characterization of potassium dihydrogen phosphate single crystals with l-arginine monohydrochloride as additive

Abstract In the search for suitable non-linear optical (NLO) materials with higher non-linear responses and good optical, thermal, mechanical properties as well as fast growth rate, an attempt has been made to grow potassium dihydrogen phosphate (KDP) single crystals doped with l -arginine monohydrochloride (LAHCl). Slow cooling as well as slow evaporation methods were employed to grow crystals. The concentration of dopants in the mother solution varied from 1 to 10 M%. The solubility data for dopant concentration were determined and are compared with those of pure KDP. Nucleation studies show that metastable zone width of KDP is enhanced by the addition of LAHCl. The effect of additives on the growth, nucleation kinetics, structural, optical and mechanical properties has been investigated. With increasing additive concentration, the growth rate was found to increase. Vicker's microhardness study shows higher mechanical stability in LAHCl-added KDP crystals, the pure ones. Moreover, the addition of LAHCl improves the quality of the crystal surface and yields highly transparent crystals with well-defined features.

Effect of irradiation of swift heavy ions on dyes-doped KDP crystals for laser applications

Abstract The organic dyes (amaranth, rhodamine and methyl orange) are doped in potassium dihydrogen phosphate (KDP) crystals. Influences of super saturation and dye concentration in the solution, on the color and crystal habit of KDP, were observed. Amaranth in the solution at low super saturation and high dye concentration colored the pyramidal section (1 0 1) of the crystals. The highly super saturated solutions produce entirely colored crystals. The concentration of dopants in the mother solution was varied from 0.1 to 10 mol%. The studies on pure and doped KDP crystals clearly indicate the effect of dopants on the crystal structure, in the absorption of IR frequencies and the non-linear optical property. Dye doping improves the NLO properties of the grown crystals. The frequencies with their relative intensities are obtained in FT-IR of pure and doped KDP. The very weak bands for dopants indicate its presence in low concentration. In view of the ever-growing importance of ion beams in optical material processing, this letter reports room temperature MeV Li + ion irradiation-induced depletion of hydrogen from single crystalline KDP which has wide applications as a non-linear optical material in optoelectronics technology. Irradiations have been performed using 50 MeV Li + ions up to a maximum dose of 2.4×10 15 ions cm −2 . Simultaneously, detecting the elastically recoiled Li atoms has done hydrogen profiling. Bare KDP crystals show hydrogen loss of 72% at the maximum dose whereas Au-coated samples show that 60 Au layer acts as a barrier to considerably reduce hydrogen depletion from KDP. A possible explanation of these phenomena is suggested.

Growth and high frequency dielectric study of pure and thiourea doped KDP crystals

AbstractNon linear optical (NLO) materials have acquired new significance with the advent of a large number of devices utilizing solid‐state laser sources. Several NLO materials have been used for this kind of technological applications. The Potassium di‐hydrogen phosphate (KDP) one of NLO material having superior non linear optical properties has been exploited for variety of applications. In the present investigation we have grown KDP crystals from aqous solution with thiourea, an organic non linear optical material. We could enhance the SHG efficiency of thiourea doped KDP crystal. It was 1.99 times more that of pure KDP. We observed more enhancements in nonlinearity for low concentration of thiourea.The crystal structure and cell parameters of grown crystal were determined from Powder XRD.The incorporation of thiourea in the grown crystals was qualitatively analyzed from FT‐IR study. The absorption spectra of pure and thiourea doped KDP crystal reveal that thiourea doped KDP crystals would be a better nonlinear optical (NLO) material for second harmonic generation (SHG) than pure KDP. The thermal decomposition and weight loss of pure and thiourea doped KDP crystal was observed by thermogravimetric (TGA) analysis and Differential Scanning Calorimetry (DSC). The high frequency dielectric study of pure KDP crystal, thiourea doped KDP crystals and organic additive thiourea was carried out using X‐band at frequency 8GHZ and 12GHZ by transmission line wave guide method. We observed low dielectric constant of thiourea doped KDP crystal when it is doped with 2mole% of thiourea. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Dielectric and polarization properties of KH2PO4 single crystals doped with Li, Na, and NH4 impurities

The dielectric and polarization properties of potassium dihydrogen phosphate (KDP) single crystals doped with Li, Na, and NH4 impurities have been investigated in the temperature range 70–150 K. It is found that the domain freezing temperature in the lithium-containing sample exceeds that for nominally pure KDP. Disappearance of freezing is observed in the ammonium-doped crystal.

Theoretical investigations of thermodynamic properties of partially deuterated K(H_{1-x}D_{x})_{2}PO_{4} ferroelectrics

The research of thermodynamic properties of partially deuterated K(H1 xDx)2PO4 crystals was performed within the framework of proton ordering model with tunnelling within the four-particle cluster approximation for short-range interaction and within the molecular field approximation for long-range interaction. The KD2PO4's model parameters were derived for the case of acceptable description of the experimental data for crystal ther- modynamic characteristics. Based on the introduced procedure of deriving parameters for K(H1 xDx)2PO4 crystals, the thermodynamic and dielectric properties of these crystals were calculated and the results were compared with the experimental ones. The problem of applying the mean crystal approximation to the analysis of physical characteristics of K(H1 xDx)2PO4 crystals was discussed. The investigations of partially deuterated ferroelectric crystals of the K(H1 xDx)2PO4 type make it possible to readily explain the thermodynamic and dynamic properties, peculiarities of the phase transitions, and the isotopic effect in the mixed ferroelectric crystals of the order-disorder type. A relatively simple structure of the KH2PO4 family of ferroelectrics and the peculiarities of their structure, related to the hydrogen bond system, allows us to use the methods and approxi- mations that provide high accuracy of calculation results. Close interplay between the theory and experiment is an essential point in the development of the physics of these crystals which makes it possible to work out adequate theoretical models and ultimately understand their physical prop- erties. Theoretic studies of the K(H1 xDx)2PO4 crystals ware carried out in the works (1-12). All studies of the mixed K(H1 xDx)2PO4 ferroelectrics were carried out within one of the modifications of the proton ordering model or within the proton-phonon model. The first model was proposed by Slater (13) and was developed and expanded in the works by Blinc (14,15), De Gennes (16), Vaks (17,18) and other researchers. Another model was proposed by Koboyashi (19) and then it was developed in the work (10). The first attempt to study the K(H1 xDx)2PO4 crystals was made by Tokunaga and Matsub- ara (1). The proton ordering model was exploited for the description of K(H1 xDx)2PO4 which was performed within the cluster approximation. In this work the assumption of the equality of all the interaction parameters for the KDP and DKDP crystals was made. The differences in the ferroelectric properties of these crystals were related to the tunnelling effects taking place in KDP: 6 0. Besides, it was assumed that the Tc(x) dependency can be obtained from the expression Tc() derived for pure KDP by replacing ! x·. However, the author failed to gain agreement between the theory and experiment for the Tc(x) dependency. Several other model theories related to the study of the dependencies of ferroelectric phase transition temperature and the Curie-Weiss constant on the deuteration level of K(H1 xDx)2PO4

Growth and properties of dyed KDP crystals

AbstractPotassium dihydrogen phosphate (KDP) crystals doped with xylenol orange (XO) and methylthymol blue (MTB) are grown from aqueous solutions by the method of solvent evaporation at room temperature under the conditions of natural convection and by the method of temperature lowering. Studied is the influence of the mother solution acidity on the character of the crystal coloration. The color and coloration intensity of the grown crystals are shown to strongly depend on the solution's pH. It is revealed that the crystal habit changes in the presence of organic dyes. The optical transmission spectra and the luminescence spectra of KDP:XO solutions and of the grown crystals are measured. The effect of thermal treatment and UV‐irradiation on the coloration stability of the crystals is studied. It is found that the laser damage threshold in the prismatic impurity rich colored sectors of KDP:XO is the same as that in the prismatic sectors of pure KDP crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of La3+ ions on growth and NLO properties of KDP single crystals

Single crystals of pure and Lanthanum added KDP crystals were grown from aqueous solution. The influence of La3+ ions in KDP crystals is studied. Isolated centers are formed by La3+ ions in KDP structure along (100) plane. La3+ ions incorporated into superficial crystal growth layer and slightly affect the growth process as they generate weak lattice stresses. The creation of these weak lattice stress is confirmed by Vickers's micro hardness test. The HRXRD analysis showed reduced structural defects in the La added KDP in the (100) plane than pure KDP. The incorporation of La in the crystal was confirmed by EDAX analysis. The Kurtz's powder SHG efficiency was found to be 1.5 times that of pure KDP. The UV-Vis transmission spectra of La added KDP showed excellent transmittance from 1100 nm to 340 nm and did not show any change in lower cutoff wavelength with respect to pure KDP. Laser damage threshold value has been determined using Q-switched Nd:YAG laser operating at 1064 nm and with 65 ns pulses in single shot mode. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Study of the phase behaviour of chemically doped KH 2 PO 4

The results show variation in phase boundaries and ionic conductivity of KH2PO4 (KDP) with the type of added impurities and temperature. At higher temperatures, irregular endothermic peaks are observed which are associated with the thermal decomposition of the samples whose onset temperature depends on the sample. Electrical characterization shows enhancement of ionic conductivity in single crystal samples either doped or radiated with respect to that of pure KDP, either polycrystalline or single crystal samples. Our results thus show that structural phase transition occurs before the thermal dehydration of KDP only on single crystal samples and the onset of this reaction depends on the distribution of the point defects induced in the sample by doping or radiation. The results are explained in terms of the rigidity of the hydrogen bonds sub-lattice which is modified by these treatments. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Development and Application of the Modified Strong Dipole-Proton Coupling Model for KDP-Type Crystals

The modified strong dipole-proton coupling (MSDPC) model, which predicted several static and dynamic dielectric properties of KDP-type ferroelectrics, was used to investigate local properties of these crystals. The results showed both order-disorder and displacive characteristics of pure KDP and DKDP, as in many other experimental studies (NMR, neutron scattering) of local properties. Paramagnetic center SeO4 3− introduced in KDP and DKDP lattice as a local probe in EPR technique was treated within MSDPC model as a “soft” impurity. Simulated dipole reorientational dynamics of the impurity showed characteristics similar to the slow local dynamics of the probe detected in an EPR experiment. Additionally, the MSDPC model was adapted to describe dielectric properties of KDP-type antiferroelectrics. Antiferroelectric phase transition of the first order and isotopic shift in Tc were reproduced.

Habit modification of nearly perfect single crystals of potassium dihydrogen phosphate (KDP) by trivalent manganese ions studied using synchrotron radiation X-ray multiple diffraction in Renninger scanning mode

The X-ray multiple diffraction technique using synchrotron radiation is applied in the preliminary study of the habit modification of KDP samples as induced by incorporation of the trivalent transition metal cation Mn3+. High-resolution Renninger scans of pure and doped KDP were carried out using 400 as the primary reflection, echoing the fact that these impurity species were segregated in the {100} growth sector. The analysis of the Renninger scans of the doped KDP crystals is consistent with the presence of the impurity species chemically bound within the KDP crystal structure, as confirmed through the suppression of the huge observed peak asymmetry, characteristic of perfect crystals. In addition, an extra Renninger-scan peak measured for the doped material is indicative of the impurity atoms occupying interstitial crystallographic sites in the lattice, a result consistent with X-ray standing-wave measurements. Renninger-scan reflection curve widths and lattice parameter measurements reveal the decrease in crystalline perfection (increased mosaic spread, η) and lattice contraction ofca0.4% in theaandclattice directions at the surface plane for the Mn3+-doped KDP samples in comparison with the undoped crystals.