Single crystals and mixed crystals of KH₂PO₄ (KDP) and NH₄H₂PO₄ (ADP) were grown with different dopant concentrations of NH₄H₂PO₄ in KH₂PO₄ in solution by Holden’s rotary crystallizer technique. The effect of additives like Borax (Na₂B₄O₇·10H₂O), seed crystal rotation rate and qualities of the crystals were studied. The half-wave voltages (in longitudinal mode) for KDP mixed with 1% ADP (by weight) were found and hence the unclamped (low frequency) electro-optic coefficients (r₆₃) were calculated for various wavelengths in the visible region of the spectrum. It was noted that the half-wave voltage increases with increase in wavelength and temperature.

The photoelastic behaviour ofkdp crystals with additives like borax,adp, nickel phosphate, manganese phosphate and sodium dihydrogen orthophosphate has been studied as a variable birefringent compensator. The dispersion of the stress birefringence with wavelength was studied for a single orientation.

A rapid quenching technique with a quenching rate of roughly 10⁶°C/sec has been developed to prepare glassy samples of ABO₃ type materials. Glasses of potassium lithium niobate have been prepared by this technique. These glasses have been characterized by x-ray diffraction, electron diffraction and differential scanning calorimetry techniques to assess the quality of the obtained glasses.

A novel solid solution in the system Bi-W-Cu-O has been synthesized and its structural and dielectric properties studied. The solid solution Bi₂O₃-(1 −x)WO₃-xCuO exists up tox=0·7; the solid solutions up tox=0·65 are orthorhombic but stabilize in tetragonal structure in a narrow range aroundx=0·7. The solid solutions are non-centrosymmetric and exhibit ferroelectric behaviour similar to their parent phase Bi₂WO₆. The Curie point of the solid solution is found to decrease with increase inx.

Glass composites of strontium tetraborate, SrB₄O₇(SBO) with bismuth vanadate, Bi₂VO_5·5 (BiV) of the composition (1 −x) SBO-x BiV (0 ≤x ≤ 0·75), have been synthesized. X-ray powder diffraction and electron microscopy indicate as-quenched composites to be amorphous and the annealed samples showed the presence of nanometer sized particles of BiV dispersed in the glassy matrix of SBO. The dielectric constant of these composites increases with increase in the volume fraction of BiV, at 300 K. The measured dielectric constant of the composite very nearly obeys the Maxwell’s relationship. Optical transmission studies confirm a steady shift in the optical absorption edge towards longer wavelengths with increase inx.

Large single crystals of an organic nonlinear optical (NLO) material, benzil, have been grown by employing an indigenously built Bridgman-Stockbarger crystal grwoth system. The dielectric constant (ε_r), dielectric loss tangent (tanδ) and impedance (Z) of these crystals, monitored along the crystallographica-axis, as a function of frequency in the 100kHz-10MHz range, exhibit sharp resonance effects in the 100–300kHz region. These strong resonance effects are attributed to the piezoelectric nature of the crystal. The origin of the appearance of the sharp peaks in the frequency variation ofε_r and tanδ is in response to the elastic resonances induced via the externally applied electric field. The resonance peak positions shift towards lower frequencies with increase in temperature as a consequence of the decrease in the stiffness coefficient (C₁₁) of the crystal.

X-ray line broadening is found to be an effective parameter to estimate the strain associated with rare earth ion (Gd³⁺)-doped polycrystalline bismuth vanadate(Bi₂VO_5·5). The strain increases with increasing Gd³⁺ concentration. It is anisotropic and found to be maximum in (111) plane. The Curie temperature which is known to decrease with increase in the rare earth ion concentration in these compounds is correlated with increase in strain.

Polycrystalline BiFeO3 and Bi$_{0.9}$Gd$_{0.1}$Fe$_{1−x}$Ti$_x$O$_3$ ($x = 0$, 0.01, 0.05 and 0.1) samples were synthesized by solid-state reaction route. Structural, magnetic and ferroelectric properties of these samples were investigated. X-ray powder diffraction (XRD) results confirmed the presence of a significant amount of Bi$_2$Fe$_4$O$_9$ impurity phase in the undoped BiFeO$_3$ sample. Mössbauer spectroscopy studies corroborated the XRD studies to confirm the presence of impurity phase.We have observed that gadolinium (Gd$^{3+}$) and titanium (Ti$^{4+}$) doping, respectively, on Bi$^{3+}$ and Fe$^{3+}$ sites facilitated a significant reduction in the impurity phase formation in BiFeO$_3$. Interestingly, Gd$^{3+}$-doping significantly reduced the impurity phase formation as compared to the undoped BiFeO$_3$ sample. This impurity phase formation was further overcome by doping higher ($x \ge 0.05$) amounts of Ti in BiFeO$_3$. The crystallographicsite occupancies of Gd and Ti were confirmed by Rietveld refinement of XRD data,Mössbauer spectroscopy and magnetization measurements. An enhancement in ferromagnetic properties along with moderate ferroelectricproperties have been observed after co-doping. There was an increasing trend in remnant polarization (Pr) with the increase in Ti concentration besides an improvement in the characteristic saturation magnetization. Our resultsdemonstrate that Gd$^{3+}$ and Ti$^{4+}$ doping could be used to enhance multifunctional properties of BiFeO3 ceramics to enable them as potential material for various devices.