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The dielectric behavior of lithium tantalate (LT) single crystals has been investigated in the vicinity of the ferroelectric phase transition for nonstoichiometric and near-stoichiometric compositions. Fitting of the experimental data to a modified Curie-Weiss equation indicates the occurrence of a mildly relaxor-ferroelectric-like phase transition in congruent LT single crystals (with the Curie-Weiss exponent γ having a value 1.2, rather than the value unity for a regular ferroelectric). As the Li concentration of these crystals approaches the stoichiometric value, the phase transition gets sharper, indicative of an increasing amount of long-range ordering. The bulk concentration of cation vacancies has also been estimated. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report the existence of anisotropic behavior along the crystallographic axes in optical, electrical and thermal properties of lithium tri borate, a recently developed vacuum UV-NLO material. The variation of refractive index with the wavelength along the crystallographic axes was investigated by prism coupling method. The results of impedance spectroscopy measurement reveal the presence of a strong anisotropy in ionic conductivity and dielectric constant along the axes and also show the super-ionic conduction behavior along the c-axis with the activation energy of Δ∼0.20eV. A thermo-mechanical study in the temperature range of 300–900K indicates the existence of a strong variation in the linear thermal expansion coefficient (positive value along the a-axis, and negative value along the c-axis) of LiB3O5 crystals. [Copyright &y& Elsevier]

The effects of Lead oxide (as solvent) content in the perovskite phase formation in spontaneous growth of PZN single crystal have been studied. In spite of adopting columbite route, 50 wt% of solvent leads to the growth of undesirable pyrochlore phase. With the increase of solvent content, the probability of formation of perovskite phase was found to increase. Growth run performed with PZN/PbO weight ratio 35:65 resulted the growth of crystals with > 98% perovskite phase present in it. With the help of oscillating thermal profile PZN single crystal was grown of the size 10 × 10 × 8 mm 3 . [ABSTRACT FROM AUTHOR]

Single crystals of 0.91PZN-0.09PT were grown by flux method. (001) oriented crystal plates were poled under different electric fields. Dielectric measurements show a phase transition peak at 460 K in unpoled samples. Poled samples show an additional anomaly around 360 K. Heat flow measurements also reflect a hump near 450 K in unpoled crystals. The hump gets diffused as we increase the poling field. As we pole the sample at 6kV/cm, before carrying out the heat flow measurement, the hump disappears. [ABSTRACT FROM AUTHOR]

Abstract: For pure SLN and SLT crystals the coercive field measured from ferroelectric hysteresis loop was found to be independent of ramp rate. Decreased lithium concentration in pure SLN samples, the coercive field and internal field are strongly enhanced. NbLi antisites are the major contribution to the internal field. Coercive field depends strongly on the ramp rate in case of MgSLN and MgSLT samples, because of domain pinning. The coercive field is considerably reduced in Mg doped SLN and SLT compared to pure samples, indicating that the switching fields are strongly dependent on the nonstoichiometry of the crystals. The coercive field values were found to be constant under multiple cycling in case of Mg (1mol%) doped SLN crystal. A strong correlation is found to exist between coercive field value and the Curie temperature. [Copyright &y& Elsevier]

Abstract: In this paper we report the growth of pure and Rhodium ion incorporated KTiOPO4 (Rh:KTP) single crystals by top seeded solution growth (TSSG) technique with an improved seeding procedure. The optical transmission/absorption spectra of pure and Rh:KTP crystals in the UV–VIS region are discussed. It is shown that the presence of Rh ion increases the indirect energy gap (E g) and shifts the lower absorption edge of KTP towards higher energy region. The ionic conductivity and dielectric properties of pure and Rh:KTP crystals were studied by means of impedance spectroscopy. The frequency and temperature dispersion behavior of dielectric constant and ionic conductivity of doped crystals are similar to pure KTP. Measured activation energies (E a) from the ionic conductivity and dielectric loss spectra indicate the existence of superionic conduction behavior. Linear thermal expansion coefficients of pure and doped crystals along the polar axis were obtained using a thermo mechanical analyzer. [Copyright &y& Elsevier]

Abstract: A thorough study reveals the importance of a proper synthesis condition in the growth of colour-free lead tungstate single crystals. An optimised synthesis scheme is described. The temperature gradient required, above the melt, for the growth of crack-free crystals is 25°C/cm. Differential thermal analysis shows that an improper synthesis results in a compositional variation along the vertical axis of the crystal. UV-visible absorption detects an enhanced absorption in the wavelength, 380–450nm for the pale yellow-coloured crystals. Annealing in air for 15h at 1050°C removes the special blue absorption in the coloured crystal. [Copyright &y& Elsevier]

Single crystals of lead zinc niobate-lead titanate (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 for x = 8% and 9% have been grown by flux method using Lead Oxide (PbO) as flux. Low scan rate XRD has been carried out to investigate on the structural influence of the compositional variations in the grown crystals. Transmission spectra in the range of UV-Vis-Near IR and mid IR regions have been carried out to understand the distortions caused in the BO6 octahedral lattice. Morphological aspects of as-grown PZN-PT crystals have also been investigated. Dielectric measurements clearly explained the dependence of Tc and diffusiveness with PT content. The values of Pr and Ecobtained from P-E loops suggest the presence of ordered domain state in these PZN-PT single crystals. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: Stability of the solution against spurious nucleation plays a dominant role in the growth of crystals at high growth rates requiring high levels of supersaturation. If any spurious nucleation does occur during a growth run, it becomes practically impossible to grow a very large crystal. A novel nucleation-trap crystallizer has been developed and used for the growth of crystals from aqueous solution so as to trap any unwanted nuclei and the particles that appear and settle at the bottom of the crystallizer during the growth process. In this crystallizer, any particles and nuclei nucleating during the growth are forced into the nucleation trap (or well) and subsequently by manipulating the temperature of the well; the growth of the nuclei is arrested. DKDP and ammonium acid phthalate crystals were grown in the developed system. X-ray rocking curve measurements on DKDP and ammonium acid phthalate crystals yielded FWHM of 89.1 and 29.71arcsec, respectively. [Copyright &y& Elsevier]

Abstract: Single crystals of 0.5 mol% Cr2O3 doped Pb(Zn1/3Nb2/3)O3 [PZN] have been grown by flux method. The dielectric and the piezoelectric properties have been investigated for <001> oriented single crystals and the results are compared with the pure PZN single crystal. The dielectric permittivity, remnant polarization and d 33 values are found to decrease on doping with chromium. On the contrary, the coercive field and quality factor (Q m) increases. All these results provide an evidence of the piezo-hardening effect, which can be attributed to the incorporation of the Cr3+ ion at the Nb5+ site rather than the Zn2+ sites. The relaxational behaviour of PZN is not much affected by doping chromium. [Copyright &y& Elsevier]

Abstract: In this investigation, ferroelectric Pb(Zn1/3Nb2/3)O3–PbTiO3 single crystals have been grown by modified flux technique with PbO self flux. Well-defined domain patterns were observed through polarized light on the as-grown crystals. Fingerprint like pattern and tweed pattern have also been observed. In PZN–PT system the fingerprint domain area is found to be elongated along one direction for increasing PT content. [Copyright &y& Elsevier]