Phase Transition Dielectric Properties in Order-disorder Antiferroelectric NH4(H2PO4) (ADP) Crystal

A modified four sublattice pseudospin lattice coupled model Hamiltonian by adding extra spin-lattice interaction, direct spin-spin interaction has been used to study dielectric properties for ammonium dihydrogen phosphate (ADP) crystal. Using the double-time temperature-dependent Green’s function method, the expressions for soft mode frequency, dielectric permittivity and loss tangent have been derived. By fitting the model values of various physical parameters, the thermal variations of the above quantities are calculated and compared with the experimental results. Our theoretical obtained results are in good agreement with experimental data.

Phase stability analysis of shocked ammonium dihydrogen phosphate by X-ray and Raman scattering studies

Impact of shock waves on non-linear optical materials bring about a lot of unknown behaviors of materials and such kinds of shock wave recovery experiments are highly required for the better understanding of material-property relationship. In the present context, we have performed experiments on the impact of structural properties of ammonium dihydrogen phosphate (ADP) samples under shock wave loaded conditions and the results of the test samples have been evaluated by X-ray diffraction (XRD), Raman spectroscopy, diffused reflectance spectroscopy (DRS) and field emission scanning electron microscopic (FESEM) technique. Interestingly, prismatic face of ADP shows loss of degree of crystallinity whereas pyramidal face shows enhancement of crystalline nature with respect to number of shock pulses due to shock wave induced dynamic re-crystallization. Hence, the present problem is worthy enough to unearth and understand the anisotropic nature of the ADP crystal and their structural modifications at shock wave loaded conditions.

Precise Method for Measuring the Quadratic Electro-Optic Effect in Noncentrosymmetric Crystals in the Presence of Natural Birefringence

The application of the improved dynamic polarimetric method for the measurement of the quadratic electro-optic effect in NH4H2PO4 (ADP) crystal with the light beam propagating perpendicularly to its optical axis is presented. This technique can be applied in noncetrosymmetric crystals in the presence of natural birefringence even when the fast and slow rays diverge slightly, causing them to only partially interfere. The method allows for minor errors in cutting and orientation of the crystal samples, resulting in deviations from configurations in which the crystal symmetry vetoes the linear electro-optic effect. The occurring contribution of the linear effect, if it is not too large, not only does not exclude the measurement of the quadratic effect, but increases its accuracy. The method does not require any prior compensation for the natural birefringence. Its sensitivity allows for quadratic electro-optic effect measurements in ferroelectrics in temperatures significantly different from the phase transition temperature or in paraelectric crystals, for which this effect is relatively small.

Effect of Dicarboxylic Acid Dopant on ADP Crystal by Slow Evaporation Method

Influence of dicarboxylic acid dopant on growth and characterization of ADP crystal were grown by slow evaporation technique at room temperature. The transparent (ADFU) crystals are yield after a period of 15 days. The X-ray diffraction study reveals that ADFU crystal belongs to tetragonal system. The vibrational modes of grown crystal were confirmed by FTIR spectral analysis. In UV-Vis spectral analysis the absorbance is low than pure ADP which reveals that NLO active of grown crystal is more. The emission spectrum of grown crystal was studied using fluorescence spectral analysis. The nonlinear optical property was analyzed using Kurtz-Perry technique, the SHG efficiency of ADFU crystal has much higher than that of pure ADP. The mechanical behavior includes binding nature and strength for the grown crystal was investigated by Vickers microhardness test.

Effect of shock waves on structural and dielectric properties of ammonium dihydrogen phosphate crystal

In this research article, the authors pay attention to investigate the effect of structural and dielectric properties of ammonium dihydrogen phosphate (ADP) crystal under pre and post shock loaded conditions. A shock wave of Mach number 1.9 was utilized for the present investigation which was generated by a table-top pressure driven shock tube. The crystalline nature and grain size variations were estimated by powder X-ray diffraction technique. The grain size of post shock wave loaded ADP crystal is found to be larger than that of the pre shock wave loaded ADP crystal. The dielectric properties of the pre and post shock loaded crystals were analyzed by impedance analyzer as a function of frequency (1 kHz–1 MHz) at ambient temperature. The dielectric constant is observed to be varying from 346 to 362 at the frequency of 400 kHz for pre and post shock wave loaded ADP crystals, respectively. The obtained results suggest that shock waves can be an alternate tool to tailor the physical properties of materials without creating any change in the original crystal system and surface morphology.