Prapun Manyum

Crystal Growth of Ferroelectric N,N′-Diphenylguanidinium Hydrogen (+)-L-Tartrate Monohydrate Single Crystals and Their Characterizations

Single crystals of a new ferroelectric material, N,N′-Diphenylguanidinium hydrogen (+)-L-tartrate monohydrate (DPT), were grown from an aqueous solution using the slow evaporation solution technique (SEST). The grown DPT crystals were subjected to powder X-ray diffraction analysis and Fourier transform infrared spectral studies. The dielectric constant and dielectric loss of the crystal were determined as a function of frequency at room temperature and the results are discussed. The result shows that a DPT single crystal has some ferroelectricity with a saturated polarization of approximately 6.5 μC/cm2 at a coercive field of about 0.5 kV/cm.

Growth and Characterization of L-Arginine Doped Potassium Dihydrogen Phosphate Single Crystals Grown by Sankaranarayanan-Ramasamy Method

Single crystals of L-arginine doped potassium dihydrogen phosphate (KDP) were grown by both conventional and Sankaranarayanan-Ramasamy (SR) methods. The grown crystals were characterized by powder X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, optical transmission, dielectric constant, and Vickers microhardness. The reflectance and extinction coefficients of the grown crystal were calculated and discussed. The variations of dielectric constant, dielectric loss, a.c. resistivity and a.c. conductivity were studied. The lower values of dielectric loss due to fewer defects were observed in SR grown L-arginine doped KDP crystals. Vickers microhardness study showed higher mechanical stability in SR method grown crystals.

Crystal Growth, Structural, Thermal, Optical, Dielectric, and Ferroelectric Characterization of Sodium Hydrogen L-Tartrate Single Crystals

Single crystals of sodium hydrogen L-tartrate (SHT) were grown by the slow evaporation solution technique (SEST) from an aqueous solution of sodium hydroxide and L-tartaric acid at 353 K. It could successfully grow a large high-quality SHT single crystal. The 20 × 20 × 10 mm3 crystal was grown under controlled ambience for 40 days. The single crystal and powder XRD spectra confirmed the formation of the SHT single crystal, while the FTIR spectrum has shown the presence of the sodium hydrogen L-tartrate within the grown crystal. There is evident that SHT crystals have high thermal stability without any decomposition and phase transition. Additionally, the SHT may be composed of large electric dipoles, and hence, possess distinct physical properties, such as dielectricity, for optical applications.

Effects of Triglycine Sulphate on Ferroelectric Behavior of Ammonium Dihydrogen Phosphate Crystals

Pure ADP and TGS doped ADP crystals were grown successfully in aqueous solution using the conventional slow evaporation technique. The structural characteristics of the grown crystals were examined by power X-ray diffraction spectroscopy. The results confirm that the samples were single crystalline with some additional planes when adding TGS dopant in the solution. Also, the results from the FT-IR show the presence of TGS in the grown ADP crystal. However, the addition of TGS did not show a strong influence on the dielectric nor the ferroelectric properties of the TGS doped ADP. Higher concentrations of TGS may be needed to improve both the dielectricity and ferroelectricity properties of ADP single crystals.

Growth of Ferroelectric Tri-Glycine Sulphate Doped Potassium Dihydrogen Phosphate Single Crystal and Its Characterization

Potassium dihydrogen phosphate (KH2PO4, KDP) single crystals have been long studied due to their non-linear optical property. Also, these crystals can exhibit some ferroelectricity when applying an external electric field. In the absence of the external field, the remaining polarization is weak, and hence, the applications of KDP in the electronic industry are limited. In order to enhance the ferroelectricity of the KDP crystals, tri-glycine sulphate (TGS) was added to the KDP solution and then the doped crystals were grown using the slow evaporation method. The results show that the properties of TGS doped KDP crystals are similar to those of the pure KDP. However, the ferroelectricity of the TGS doped KDP has been improved by the small addition of the TGS. These reveal that the TGS molecules may disrupt the KDP lattice and hence, lead to the enhancement of the built-in polarization.

Fabrication of nanocrystalline CuO powder and giant dielectric properties of its ceramic

CuO nanoparticles of 80 nm were successfully prepared by solution method. X-ray diffraction and scanning electron microscopy were used to characterize the phase formation and microstructure of the CuO powder and ceramics, respectively. CuO ceramics were obtained by sintering the CuO nanocrystalline powder at 900 (PR-900) and 950 °C (PR-950) for 10 h in air. Giant dielectric properties of the sintered CuO ceramics were investigated as functions of temperature, frequency, dc bias, and uniaxial compressive stress. It was found that the uniaxail compressive stress and dc bias had a remarkable effect on the giant low-frequency dielectric properties of the CuO ceramics.