Department of Physics

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We synthesized zinc titanate nanopowder in different crystal structures by varying calcination temperature and time and phase evolution is qualitatively investigated using reference intensity ratio (RIR) approach. The electronic properties showed 2.9 eV as indirect band transition, and 3.59 ± 0.02 eV as direct band transition for the highest temperature annealed rhombohedral ZnTiO3 and cubic spinel Zn2TiO4 zinc titanate materials. The intermediate temperature annealed (∼850 °C) material consists of ZnTiO3, Zn2TiO4, and Zn2Ti3O8 zinc titanate nanopowder, showing similar two electronic transitions. Zinc titanate with dominant rhombohedral phase ZnTiO3 (900 °C annealed) and dominant Zn2Ti3O8 phase (750 °C annealed) are used to synthesize mesoporous electrodes for integrating the ZnS passivated CdS quantum dots. Finally, Cu2S counter electrode is integrated with polysulfide electrolyte to realize 1 cm2 area quantum dot sensitized solar cells (QDSSCs). QDSSCs with dominant ZnTiO3 phase are showing lower photovoltaic performance (short circuit current 0.76 mA/cm2, open circuit voltage 0.55 V) with respect to that of dominant Zn2Ti3O8 phase with 2.2 mA/cm2 short circuit current and 0.69 V open circuit voltage, respectively. The observed difference is attributed to differences in electronic and morphological properties of the synthesized zinc titanate powders. © 2018 Elsevier Ltd

World University root node

Solar Energy

Nanostructured zinc titanate wide band gap semiconductor as a photoelectrode material for quantum dot sensitized solar cells

BiFeO3 thin films are deposited on FTO coated glass substrates using a simple sol-gel process, limiting thickness about 70 nm and Ag/BiFeO3/FTO RRAM devices are prepared. The devices showed low-voltage bipolar switching with the maximum Ion/Ioff ratio ∼450, and low set and reset voltages ∼1.1 V and −1.5 V, respectively. The devices are stable against on-off cycles with ∼104 s retention time without any significant degradation. The variations in the set and reset voltages are 0.4 V and 0.6 V, respectively. We found that ohmic and trap-controlled space charge limited conductions are responsible for low and high resistance states, respectively. The resistive switching mechanism is attributed to the formation and rupturing of the metal filament during the oxidation and reduction of Ag ions for the set and reset states. The devices showed strong robustness against environmental conditions even after ten months from their synthesis and first measurements, exhibiting good reproducibility, retention and endurance. © 2018 Elsevier Ltd

Fulltext

Superlattices and Microstructures

Robust non-volatile bipolar resistive switching in sol-gel derived BiFeO3 thin films

Two meteorite fragments collected from the Mukundpura impact site, Rajasthan, India have been analysed using scanning electron microscopy, energy dispersive X-ray spectroscopy, Mössbauer spectroscopy, thermogravimetric analysis (TGA) and Raman spectroscopy. High Fe (22.65 wt%), Ni (1.53%) and S (3.69%) and concentrations of other elements obtained by X-ray analysis indicate that it is a carbonaceous chondrite. Mössbauer spectra show similarity with those obtained from Cold Bokkeveld and Murchison carbonaceous chondrites, and this analogy allows us to classify it as belonging to CM group of carbonaceous chondrites. TGA shows large weight loss, implying presence of significant amount of volatiles in this meteorite and Raman spectroscopy shows the presence of abundant organic matter consisting of disordered and aromatic (graphitic or polyaromatic) carbon. These results indicate that Mukundpura meteorite is a rare type of extraterrestrial object deserving further in-depth studies.

Current Science

Characterization of Mukundpura carbonaceous chondrite

Radiation calorimeter is a device for assessment of the incident local concentrated solar irradiance (CSI) onto a receiver surface. This is required to evaluate the performance of a concentrated solar thermal system using, for instance a volumetric receiver, for applications. In this paper a low-temperature water cooled radiation calorimeter (RADCAL) is presented. This is designed as a cavity based on the concept of blackbody to maximize the absorption of the incident CSI on its absorber surfaces. Solar selective coatings are deposited on its reflector and absorber surface to achieve the same and are characterized using standard methodologies. This depicts an absorptivity of 0.95 and a reflectivity of 0.87 in the desired range of the solar spectrum and is theoretically verified. The absorption of energy results in temperature rise of RADCAL, which is controlled by an external water jacket to limit its value at 100 °C for mitigating the use of pressurized water. At any instant and eventually at the steady-state the CSI is estimated following the conservation of energy principle. The developed RADCAL is experimentally evaluated up to a CSI of 800 Suns (1 Sun = 1 kW/m2) using Joule heating. The entire heat transfer process is analysed with the developed unsteady state one-dimensional mathematical model. A comparative assessment of the measured and calculated RADCAL body temperature provides the underlying uncertainty and confirms its design basis. Furthermore, the design and given consideration allows its use in arid desert condition with dust and wind. Thus, RADCAL is likely to serve in future for evaluating concentrated solar thermal system in arid deserts. © 2018 Elsevier Ltd

A low temperature water-cooled radiation calorimeter for estimation of concentrated solar irradiance

In this work we study temporal quantum correlations, quantified by Leggett-Garg (LG) and LG-type inequalities, in the B and K meson systems. We use the tools of open quantum systems to incorporate the effect of decoherence which is quantified by a single phenomenological parameter. The effect of CP violation is also included in our analysis. We find that the LG inequality is violated for both B and K meson systems, the violation being most prominent in the case of K mesons and least for Bs system. Since the systems with no coherence do not violate LGI, incorporating decoherence is expected to decrease the extent of violation of LGI and is clearly brought out in our results. We show that the expression for the LG functions depends upon an additional term, apart from the experimentally measurable meson transition probabilities. This term vanishes in the limit of zero decoherence. On the other hand, the LG-type parameter can be directly expressed in terms of transition probabilities, making it a more appropriate observable for studying temporal quantum correlations in neutral meson systems. © 2018 American Physical Society.

Physical Review D

Study of temporal quantum correlations in decohering B and K meson systems

Recent measurements of RD∗ have reduced tension with the Standard Model prediction. Taking all the present data into account, we obtain the values of the Wilson coefficients of each new physics four-fermion operator of a given Lorentz structure. We find that the combined data rule out most of the solutions based on scalar/pseudoscalar operators. By studying the inter-relations between different solutions, we find that there are only four allowed solutions, which are based on operators with (V − A), linear combination of (V − A) and (V + A), tensor and linear combination of scalar/pseudoscalar and tensor structure. We demonstrate that the need for new physics is driven by those measurement of RD and RD∗ where the τ lepton is not studied. Further, we show that new physics only in b→cμν¯ is not compatible with the full set of observables in the decays B→ Dlν¯ and B→ D*lν¯. © 2018, The Author(s).

Journal of High Energy Physics

New physics solutions for RD and RD∗

A field experiment was conducted on micro plots (2 m × 2 m) at Research Farm of CCS Haryana Agricultural University, Hisar, India to study the effect of different fertigation levels of tomato crop using good quality water through drip irrigation. There were three fertigation levels of nitrogen i. e. N1-75% of recommended dose of nitrogen (RDN), N2-100% RDN and N3-125% RDN. The volume of irrigation water applied per plant during an irrigation event was calculated based on crop spacing, pan evaporation, crop coefficient and per cent shaded area. A total of 948.4 litre of water was applied to each micro plot during the entire crop period. Soil moisture in profile of different treatments was taken at fortnight interval. 1/3 rd of nitrogen was applied before the transplanting of tomato plants. Remaining dose was equally split in 11 doses at weekly interval. Maximum tomato yield (61.53 t/ha) and water use efficiency (WUE = 26.0 kg/m3) were obtained with nitrogen fertigation level N3. Minimum tomato yield (43.25 t/ha) and water use efficiency (18.2 kg/m3) were obtained with nitrogen fertigation level N1. Maximum nitrogen use efficiency (NUE) (594.9 kg of tomato/kg of nitrogen) was obtained with fertigation level N2 and minimum NUE (492.2 kg of tomato/kg of nitrogen) was obtained with fertigation level N3 © 2018 Agri. Bio. Publishers. All rights reserved.

Annals of Biology

Evaluation of the effect of nitrogen fertigation on tomato under drip irrigation

Strong interest exists in the development of organic–inorganic lead halide perovskite photovoltaics and of photoelectrochemical (PEC) tandem absorber systems for solar fuel production. However, their scalability and durability have long been limiting factors. In this work, it is revealed how both fields can be seamlessly merged together, to obtain scalable, bias-free solar water splitting tandem devices. For this purpose, state-of-the-art cesium formamidinium methylammonium (CsFAMA) triple cation mixed halide perovskite photovoltaic cells with a nickel oxide (NiOx) hole transport layer are employed to produce Field's metal-epoxy encapsulated photocathodes. Their stability (up to 7 h), photocurrent density (–12.1 ± 0.3 mA cm−2 at 0 V versus reversible hydrogen electrode, RHE), and reproducibility enable a matching combination with robust BiVO4 photoanodes, resulting in 0.25 cm2 PEC tandems with an excellent stability of up to 20 h and a bias-free solar-to-hydrogen efficiency of 0.35 ± 0.14%. The high reliability of the fabrication procedures allows scaling of the devices up to 10 cm2, with a slight decrease in bias-free photocurrent density from 0.39 ± 0.15 to 0.23 ± 0.10 mA cm−2 due to an increasing series resistance. To characterize these devices, a versatile 3D-printed PEC cell is also developed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Advanced Energy Materials

Scalable Triple Cation Mixed Halide Perovskite–BiVO4 Tandems for Bias-Free Water Splitting

We collected the information of 304 gamma-ray bursts (GRBs) from the literature, and analyzed the correlations among the host galaxy offsets (the distance from the site of the GRB to the center of its host galaxy), T90,i (the duration T90 in rest-frame), TR45,i (the duration TR45 in rest-frame), Eγ,iso (the isotropic equivalent energy), Lγ,iso (=Eγ,iso/T90,i, the isotropic equivalent luminosity) and Lpk (peak luminosity). We found that T90,i, TR45,i, Eγ,iso, Lpk have negative correlation with offset, which is consistent with origin of short GRBs (SGRBs) and long GRBs (LGRBs). On separate analysis, we found similar results for log⁡Eγ,iso−log⁡(offset) and log⁡Lpk−log⁡(offset) relations in case of SGRBs only, while no obvious relation for LGRBs. There is no correlations between offset and Lγ,iso. We also put the special GRB 170817A and GRB 060218A on the plots. The two GRBs both have low luminosity and small offset. In the log⁡(offset)−log⁡T90,i plot, we found GRB 170817A locates in between the two regions of SGRBs and LGRBs and it is the outlier in the offset−Eγ,iso, offset−Lγ,iso and offset−Lpk plots. Together with GRB 060218A being an outlier in all plots, it indicates the speciality of GRBs 170817A and 060218A, and might imply more subgroups of the GRB samples. © 2018 Elsevier B.V.

Journal of High Energy Astrophysics

Possible correlations between gamma-ray burst and its host galaxy offset

Emerging autonomous electronic devices require increasingly compact energy generation and storage solutions. Merging these two functionalities in a single device would significantly increase their volumetric performance, however this is challenging due to material and manufacturing incompatibilities between energy harvesting and storage materials. Here we demonstrate that organic-inorganic hybrid perovskites can both generate and store energy in a rechargeable device termed a photobattery. This photobattery relies on highly photoactive two-dimensional lead halide perovskites to simultaneously achieve photocharging and Li-ion storage. Integrating these functionalities provides simple autonomous power solutions while retaining capacities of up to 100 mAh/g and efficiencies similar to electrodes using a mixture of batteries and solar materials. © 2018 American Chemical Society.