V.K. Wadhawan

Growth and characterization of PbB4O7 single crystals

Abstract Good-quality and fairly large-sized single crystals of PbB 4 O 7 (PbO·2B 2 O 3 ) were grown by the top-seeded melt-growth method. The transparency range of these crystals was measured to be 240–3600 nm. The transmission fraction for an as-grown crystal plate was found to be ∼80%. Characterization of the grown crystals was carried out using X-ray diffraction, DTA/TG, and X-ray fluorescence techniques to establish their quality.

Studies on Nonlinear Optical Properties of Ferroelectric MgO-LiNbO3 Single Crystals

Undoped and MgO doped LiNbO3 crystals were grown by Czochralski technique. Blue shift in absorption edge was observed with MgO doping. The nonlinear optical properties of undoped and doped crystals were measured experimentally using Kurtz powder SHG analysis. According to defect structure model, the relative SHG efficiency is critically MgO doping and Li/Nb ratio dependant. The NLO coefficient were observed 40 times higher than KDP for undoped and 3 mol.% MgO doped crystals.

Effect of Oxygen Annealing on Domain Structure and Dielectric Properties of 0.91PZN-0.09PT Single Crystal

Single crystals of 0.91PZN-0.09PT were grown by flux method. Annealing of the crystals under oxygen atmosphere leads to stripe like domains. Dielectric properties were found to be enhances after oxygen annealing. P-E hystersis show increase in the remnant polarization and coercive field. Heat flow measurement does not reflect any significant change in the properties after oxygen annealing. Phase transition temperature remains the same for as grown and oxygen annealed samples. However, a little increase of the phase transition enthalpy is observed in oxygen annealed crystals. The change in properties due to oxygen annealing has been explained in terms of defect movement in the crystals.

Growth of 0.91PZN-0.09PT Single Crystal and Effect of Poling on Their Properties

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.

Growth of Relaxor Ferroelectric Single Crystals PbZn1/3Nb2/3O3 (PZN) by High Temperature Solution Growth

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 .