Mohan D. Aggarwal

Present Status of Polymer : Ceramic Composites for Pyroelectric Infrared Detectors

‘Ferroelectrics:Polymer’ composites can be considered an established substitute to conventional electro-ceramics and to ferroelectric polymers. The composites have unique blend of polymeric properties such as mechanical flexibility, high strength, formability, and low cost with high electro-active properties of ceramic materials. It has attracted considerable interest because of their potential use in pyroelectric infrared detecting devices and piezoelectric transducers. These flexible sensors and transducers may eventually be useful for NASA crew launch vehicles and crew exploration vehicles being developed for their health monitoring applications. In the light of many technologically important applications in this field; it is worthwhile to present an overview of the pyroelectric infrared detector theory, models to predict dielectric behavior and pyroelectric coefficient in conjunction with the concept of connectivity and fabrication techniques of biphasic composites. An elaborate review of ‘Pyroelectric: Polymer’ composite materials investigated to date for their potential use in pyroelectric infrared detectors is presented.

Triboluminescent materials for smart sensors

Since the beginning of 21 st Century, scientists and engineers have been investigating triboluminescent materials for use in smart impact sensors. One of the brightest triboluminescent materials found thus far is europium dibenzoylmethide triethylammonium (EuD 4 TEA). This material was discovered by Hurt in 1966 and is bright enough to be seen in daylight. Through innovative design of the material synthesis steps and by exchanging europium chloride for europium nitrate, the triboluminescent emission was increased by over 80%. In addition, the material yield was increased, as chloride washing is not required. Here, we discuss the new synthesis process, triboluminescent results, and future applications of EuD 4 TEA phosphors.

Perovskites: transforming photovoltaics, a mini-review

Abstract. The recent power-packed advent of perovskite solar cells is transforming photovoltaics (PV) with their superior efficiencies, ease of fabrication, and cost. This perovskite solar cell further boasts of many unexplored features that can further enhance its PV properties and lead to it being branded as a successful commercial product. This article provides a detailed insight of the organometal halide based perovskite structure, its unique stoichiometric design, and its underlying principles for PV applications. The compatibility of various PV layers and its fabrication methods is also discussed.

Growth and characterization of doped DTGS crystals for infrared sensing devices

Abstract Modified deuterated triglycine sulfate (DTGS) single crystals have been grown from the deuterated aqueous solution simultaneously doped with l -alanine and neodymium sulfate in the ferroelectric phase using temperature-lowering technique. The effects of these different dopants on the growth, dielectric and pyroelectric properties have been investigated. Doped crystals exhibited higher material figures of merit for pyroelectric infrared sensing devices and vidicons applications with wider operating temperature, compared with virgin DTGS crystals.

SrI2, a Novel Scintillator Crystal for Nuclear Isotope Identifiers

The growth and scintillating properties of undoped and Eu2+ doped Strontium Iodide indicate excellent potential for gamma ray spectroscopy. Energy resolution at 662 keV was found to be as good as 2.7% at 662 keV. The effect of purification by zone refining was also studied and crystal growth of SrI2 by the Bridgman technique was found to be less subject to cracking compared to the growth of lanthanum halide scintillators.

Comparison of the triboluminescent properties for europium tetrakis and ZnS:Mn powders

In 2006, some authors determined that the triboluminescence (TL) of manganese-doped zinc sulfide (ZnS:Mn) increases with increasing impact velocity. In 2011, the authors discovered a method of synthesizing europium dibenzoylmethide triethylammonium (EuD4TEA) that produced TL 106% greater than ZnS:Mn. In fact, this material is bright enough to be seen in daylight. This paper investigates the effects of increasing impact energy on the TL of EuD4TEA and various grain sizes of ZnS:Mn using a drop tower. The low energy results indicate that increasing impact energy can increase the triboluminescent light yield for impact energies up to 1.4 J, the upper limit of the drop tower. The minimum activation energies required for each material are also explored. In addition, the effects of the increasing impact energy on the triboluminescent decay time are also investigated. The details of the experimental setup, synthesis of EuD4TEA, and results are discussed in this paper.

Crystal growth and optical properties of 4-aminobenzophenone crystals for NLO applications

Single crystals of 4-aminobenzophenone, a nonlinear optical (NLO) material have been grown successfully by a novel solution growth as well as modified Bridgman-Stockbarger techniques. The transmission spectrum (420-1400 nm) and SHG efficiencies were determined. 4-Aminobenzophenone crystals gave a lower limit on the second harmonic generation (SHG) efficiency of 10%. Laser damage threshold measurements conducted at the indicated wavelengths gave values of 1-2 GW/cm 2 .

Comparison of the triboluminescent yield and decay time for europium dibenzoylmethide triethylammonium synthesized using different solvents

Europium dibenzoylmethide triethylammonium (EuD4TEA) is one of the brightest known triboluminescent (TL) materials. First synthesized in 1966, emission from EuD4TEA is bright enough to be seen in daylight. In this paper we report the synthesis of Eu(III) tetrakis compounds using different solvents, and their influence on the appearance, TL yield, and decay time. The physical appearance of Eu compounds changed with the solvent type. Further, the solvents influenced the time for nucleation and completion of the reaction. TL measurements show that Eu tetrakis compounds derived from acetone solvent had the largest emission, while the smallest emission with the shortest decay time was obtained for the product from chloroform solvent. Photoluminescent emission spectra for the compounds from different solvents show the 5D0 → 7F1, 5D0 → 7F2 and 5D0 → 7F3 peaks which are consistent with previously reported results for EuD4TEA. However the intensity of the 5D0 → 7F2 transition shows the 613.5 nm is larger than the 611.7 nm for the products from 1-butanol and methylene chloride. Eu compound from 1-butanol shows a more intense 616.5 nm and 624.2 nm peaks, of which the later peak is almost merged into the background for Eu compounds obtained from the other solvents.

Oscillatory behavior of spatial solitons in two-dimensional waveguides and stationary temporal power law solitons in optical fibers

The one-particle type temporal soliton exists by maintaining a balance between dispersive linear contributions on the one hand and non-linear effects on the other. The linear contributions occur from processes such as group velocity and polarization mode dispersion. The non-linear features occur from Kerr, or power law non-Kerr behavior. In addition, a variety of perturbations, such as damping, Brillouin scattering, and Raman effects exist to alter the simple soliton solution. In this paper, we review the propagation of temporal solitons in power law non-Kerr media. This is developed through the higher nonlinear Schrödingers equation (HNLSE). Also, the fundamentals of multiple-scales are presented that will be used to yield quasi-stationary solitons when perturbations are present. In waveguides, the one-particle type spatial soliton exists by maintaining a balance between the linear propagational diffraction and non-linear self-focusing, while possibly being subjected to a variety of perturbations. Here, we use a spatial optical soliton solution to the nonlinear Schrödinger equation in an inhomogeneous triangular refractive index profile as a small index perturbation to illustrate the oscillation property within a two dimensional waveguide. We determine, from the motion of spatial soliton, its effective acceleration, period of oscillation, and compare results with the Gaussian refractive index profile. Such spatial solitons behave as point masses existing in a Newtonian gravitational potential hole.

Luminescent properties of lanthanide dibenzoylmethide triethylammonium compounds

Triboluminescence (TL) is defined as the emission of cold light based on mechanical action. In 1999, Sage and Geddes used this property to design a sensor capable of discerning the location of impacts. By coating a structure with various triboluminescent materials, impacts to structures could be monitored with simple light detectors. However, the intensity of most materials is very low. Of the thousands of known triboluminescent materials, only a few can emit enough light to be seen in daylight. One of these materials is europium dibenzoylmethide triethylammonium (EuD4TEA). This material shows 206% of the TL yield compared to the more commonly known manganese-doped zinc sulfide. Due to the high TL yield of EuD4TEA, exploration of the lanthanide series compounds was attempted for different emission wavelengths. This will help to monitor the locations of impacts on structures. This paper will investigate the TL yields, TL decay times, and the spectra of various lanthanide dibenzoylmethide triethylammonium compounds.PACS78.60.Mq, 78.55.Bq, 71.20.Eh