K. D. Parikh

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.

Vickers Micro-Hardness Studies of Amino Acids (L-Histidine, L-Threonien and DL-Methionine) Doped KDP Crystals

Pure and various amino acids (L-histidine, L-threonine, DL-methionine) doped KDP crystals were grown by slow solvent evaporation technique. The doping of amino acids was confirmed by C, H, N analysis, FTIR spectroscopy and paper chromatography .Pure and doped KDP crystals were subjected to Vickers microhardness studies. Indentations were made on smooth (100) as grown faces of pure and doped crystals. The Vickers indenter loads were varied from 0.298 N to 0.981 N in order to study the effect of load on microhardness. A number of indents were made at each load and the mean diagonal length (d) was used in calculating the Vickers Hardness Number (HV). The Vickers micro-hardness decreased as amino acid doping level was increased indicating that the KDP crystals became softer after doping. The Indentation size effect (ISE) the Kicks law as well as PSR model was verified for all samples. The values of the load independent hardness and the Newtonian pressure (W) were higher in pure KDP crystals than the amino acids doped KDP crystals. It was found that as the doping concentration of amino acids increased the values of load independent hardness and Newtonian pressure decreased. Hays and Kendall law analysis was also applied to the hardness data.

Dielectric relaxation, protonic defect, conductivity mechanisms, complex impedance and modulus spectroscopic studies of pure and L-threonine-doped ammonium dihydrogen phosphate

Ammonium dihydrogen phosphate (ADP) has a wide range of applications in integrated and nonlinear optics. The dopant-like L-threonine has hydrogen-bonded side chain that causes defects in ADP. The pure and L-threonine-doped ADP crystals are grown using slow evaporation technique. The powder XRD patterns show the single-phase nature of pure and doped ADP. The dielectric constant and dielectric loss have shown the usual behaviour with respect to frequency and temperature. The protonic conduction is prevailing for electric transport, and from Jonscher’s plot, the correlation barrier hopping (CBH) and non-overlapping small polaron tunnelling (NSPT) conduction mechanism is confirmed. The Nyquist plot and modulus spectra show the presence of grain and grain boundary. The stretch exponent exhibits non-Debye-type relaxation. The activation energy of relaxation time for all samples is calculated. The modulus master curve and variation of Z″ and M″ versus angular frequency confirmed the proposed conduction. The nonlinear optical counterpart is in accordance with dielectric results.

Raman, photoluminescence, and a.c. electrical studies of pure and L-serine doped ammonium dihydrogen phosphate single crystals: an understanding of defect chemistry in hydrogen bonding

Ammonium dihydrogen phosphate (ADP) crystals have a wide range of nonlinear optical applications. The hydrogen bond side chain contains dopant like L-serine causing defects in ADP. The pure and L-serine doped ADP crystals are grown using a slow evaporation technique. The powder XRD patterns show the single-phase nature of the pure and doped ADP crystals. The FT-Raman spectra show the presence of a variety of normal modes of vibrations of ADP. The photoluminescence study suggests an increase of the Stokes shift and the presence of vibrational energy relaxation phenomena. a.c. electrical studies such as dielectric, impedance and modulus spectroscopy were carried out to elucidate the behaviour of the charge carrier under the course of the alternating electrical field. The defect oriented correlated barrier hopping (CBH) conduction mechanism, the presence of grains and grain boundaries, and the non-Debye type relaxation phenomena are explained. The nonlinear second harmonic generation efficiency of the grown crystals is found to be improved on doping L-serine in ADP.

Growth and characterization of L-tryptophan doped KDP crystals

Potassium Dihydrogen Phosphate crystals are one of the most popular crystals used for Non-linear Optical applications. Most of the amino acids also exhibit NLO properties. The effect of doping of one of the amino acids, L-tryptophan in KDP crystals has been investigated. Pure and L-tryptophan doped KDP crystals were grown by slow solvent evaporation solution growth technique. Good quality transparent crystals were obtained. Doping of L-tryptophan in KDP crystal was confirmed by FT-IR spectroscopy studies. The value of second harmonic generation efficiency and optical transmission in UV-Vis spectra increased as doping of L-tryptophan increased in KDP crystals.

Powder XRD and dielectric studies of gel grown calcium pyrophosphate crystals

Formation of calcium pyrophosphate dihydrate (CPPD) crystals in soft tissues such as cartilage, meniscus and synovial tissue leads to CPPD deposition diseases. The appearance of these crystals in the synovial fluid can give rise to an acute arthritic attack with pain and inflammation of the joints, a condition called pseudo-gout. The growth of CPP crystals has been carried out, in the present study, using the single diffusion gel growth technique, which can broadly mimic in vitro the condition in soft tissues. The crystals were characterized by different techniques. The FTIR study revealed the presence of various functional groups. Powder XRD study was also carried out to verify the crystal structure. The dielectric study was carried out at room temperature by applying field of different frequency from 500 Hz to 1 MHz. The dielectric constant, dielectric loss and a.c. resistivity decreased as frequency increased, whereas the a.c. conductivity increased as frequency increased.

Dielectric and Spectroscopy Studies of L-Arginine Doped Potassium Dihydrogen Phosphate

Potassium dihydrogen phosphate (KDP) is a well known nonlinear optical (NLO) material having different applications in electro-optics and laser technology. Pure and amino acid L-arginine doped KDP single crystals were grown by the slow solvent evaporation technique. The 0.3, 0.4 and 0.5 weight % doping of L-arginine was successfully achieved in KDP crystals and confirmed by paper chromatography, CHN analysis, FTIR and UV-Vis spectroscopies. The dielectric behaviour 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 is reported. The effect of amino acid doping was observed on SHG efficiency. The results are discussed.

Growth and Characterization of DL-Methionine Doped KDP Crystals

Potassium Dihydrogen Phosphate (KDP) crystals are one of the most popular crystals used for Non-linear Optical (NLO) applications. Most of the amino acids also exhibit NLO properties; therefore, the effect of doping of one of the amino acids, DL-methionine, in KDP crystals has been investigated. Pure and DL-methionine doped KDP crystals were grown by slow solvent evaporation solution growth technique. For growing the doped crystal, 0.3 and 0.4 weight percent DL-methionine was added to aqueous solution of KDP. Good quality transparent crystals were obtained within 8 to 10 days. Doping of amino acid DL-methionine in grown crystals was confirmed by the CHN analysis and FT-IR spectroscopy studies. The powder XRD indicated the single phase nature of samples and the unit cell parameters were not altered much due to doping. The value of second harmonic generation (SHG) efficiency and optical transmission in UV-Vis spectra increased as the doping of DL- methionine increased in KDP crystals. The variation of dielectric constant, dielectric loss (tanδ), with frequency of applied field in the range from 100 Hz to 100 kHz is reported. The dielectric constant and dielectric loss decreased with increase the value of frequency of applied field. The dielectric constant and the dielectric loss of DL- methionine doped KDP crystals were lower than the pure KDP crystals. Thermal stability of the grown crystals was studied by employing thermo-gravimetry analysis (TGA). It was found that the doping of DL-methionine decreased thermal stability of KDP marginally, but enhanced optical properties.