Amino acid family crystals exhibit excellent nonlinear optical and electrooptical properties. L-Alanine single crystal belongs to the amino acid group and has been grown by the slow evaporation solution growth technique at room temperature. The grown crystals were characterized by high-resolution X-ray diffractometry (HRXRD), nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, UV-Vis, Raman spectroscopy, mass spectra analyses and density measurements. Its laser damage threshold was measured and its nonlinear optical response was tested by using a Q-switched Nd:YAG laser, and the value of laser damage threshold is greater than that of potassium dihydrogen phosphate (KDP).

Lead free piezoelectric single crystals of sodium potassium niobate (K 0.5 Na 0.5 )NbO 3 (KNN) were grown by high-temperature solution method using two different fluxes; one with a mixture of NaF and KF and other with addition of B 2 O 3 along with the mixture. In the present study, the growth of KNN crystals without B 2 O 3 flux and the same with B 2 O 3 flux were compared. It was found that additions of small amounts of B 2 O 3 lowered the melting temperature of the solid solution and enabled better dielectric properties. Phase analysis showed that all samples were crystallized in pure orthorhombic perovskite phase. AFM morphological studies showed that the addition of B 2 O 3 flux increased the roughness of the grown crystal. Further, addition of B 2 O 3 flux slightly decreased the orthorhombic to tetragonal phase transition temperature T (O-T) and the Curie temperature T C . The ferroelectric behaviour of KNN single crystal has been investigated at room temperature. The crystal grown using B 2 O 3 flux exhibited a remanent polarization (P r ) ∼ 32 μC/cm 2 and coercive field (Ec) of ∼11.8 kV/cm whereas the crystal grown without the use of B 2 O 3 flux had a remanent polarization (P r ) ∼ 36 μC/cm 2 and coercive field (Ec) of ∼14.6 kV/cm.

Abstract-Lead free piezoelectric single crystals of (K 0.5 Na 0.5 )NbO 3 and 0.5 wt%, 1.0 wt% and 1.5 wt% MnO 2 doped (K 0.5 Na 0.5 )NbO 3 (KNN) were grown by high-temperature solution method using K 2 CO 3 -Na 2 CO 3 eutectic composition as flux with addition of small amounts of boron oxide for lowering the melting temperature. The effect of the manganese dopant on the dielectric properties, surface morphology and the domain structure were investigated. The MnO 2 -doped KNN crystals were found to exhibit higher dielectric permittivity when compared with pure KNN single crystal. Mn doping increases the dielectric constant and decreases the dielectric loss. A slight decrease in the orthorhombic to tetragonal phase transition temperature T (O-T) and Curie temperature T C has been observed in manganese-doped KNN single crystals. From SEM and AFM analysis, the domain size of KNN-Mn crystal was found to be of the order of 5-13 µm at room temperature which is smaller than that of the pure KNN crystal (20-30 µm).

Abstract-Lead free piezoelectric single crystals of sodium potassium niobate (K0.5Na0.5)NbO3 and 0.5wt%, 1wt%, 1.5wt% of copper oxide CuO doped sodium potassium niobate (K0.5Na0.5)NbO3 (KNN) single crystals were grown by hightemperature solution method and the dielectric properties, morphology and domain pattern were investigated. The flux used during crystal growth is eutectic mixture of potassium carbonate K2CO3 and sodium carbonate Na2CO3. Additions of small amounts of boron oxide B2O3 further lower the melting temperature of the eutectic mixture. It was found that 1.5wt% CuO doped single crystals of sodium potassium niobate exhibits excellent dielectric properties. XRD results showed sharp peaks indicating good crystalline behavior of both pure and CuO doped KNN crystals. Phase analysis showed that all samples crystallized in pure orthorhombic perovskite phase. A slight decrease in the diffraction angles has been observed with increase in doping concentration. This is due to the replacement of Nb5+ ions by Cu2+ ions, leading to the formation of higher oxygen vacancies with the doping concentrations.

No abstract

No abstract

Abstract

Lead free piezoelectric single crystals of (K 0.5 Na 0.5)NbO 3 have been successfully grown by the high temperature flux solution method using B 2 O 3 flux. Structure of the grown KNN single crystals was confirmed by powder X-ray diffraction analysis. The chemical composition of the as-grown single crystal was determined by Energy Dispersive X-ray analysis (EDS). Dielectric properties and the domain structure of KNN single crystals were investigated. The two phase transition temperatures of orthorhombic-to-tetragonal (O-toT) and tetragonal-to-cubic (T-to-C) are found to be around 210°C and 429°C respectively for KNN single crystals as revealed from the dielectric measurements. The surface roughness was estimated to be about 6.96nm at room temperature using AFM studies. The Raman spectrum shows the characteristic peaks υ 1, υ 2 and υ 5 of KNN single crystals, which are correlated to the internal vibrations of the NbO 6 octahedron. The formation of single crystal of (K 0.5 Na 0.5)NbO 3 requires sintering below 1000°C to avoid the problem of potassium volatilization.