A codoping route to realize low resistive and stable p-type conduction in (Li, Ni):ZnO thin films grown by pulsed laser deposition

We report on the growth of Li-Ni codoped p-type ZnO thin films using pulsed laser deposition. Two mole percent Li monodoped ZnO film shows highly insulating behavior. However, a spectacular decrease in electrical resistivity, from 3.6 × 10(3) to 0.15 Ω cm, is observed by incorporating 2 mol % of Ni in the Li-doped ZnO film. Moreover, the activation energy drops to 6 meV from 78 meV with Ni incorporation in Li:ZnO lattice. The codoped [ZnO:(Li, Ni)] thin film shows p-type conduction with room temperature hole concentration of 3.2 × 10(17) cm(-3). Photo-Hall measurements show that the Li-Ni codoped p-ZnO film is highly stable even with UV illumination. XPS measurements reveal that most favorable chemical state of Ni is Ni(3+) in (Li, Ni): ZnO. We argue that these Ni(3+) ions act as reactive donors and increase the Li solubility limit. Codoping of Li, with other transitional metal ions (Mn, Co, etc.) in place of Ni could be the key to realize hole-dominated conductivity in ZnO to envisage ZnO-based homoepitaxial devices.     

Steam leak detection in advance reactors via acoustics method

Prediction of LOCA (loss of coolant activity) plays very important role in safety of nuclear reactor. Coolant is responsible for heat transfer from fuel bundles. Loss of coolant is an accidental situation which requires immediate shut down of reactor. Fall in system pressure during LOCA is the trip parameter used for initiating automatic reactor shut down. However, in primary heat transport system operating in two phase regimes, detection of small break LOCA is not simple. Due to very slow leak rates, time for the fall of pressure is significantly slow. From reactor safety point of view, it is extremely important to find reliable and effective alternative for detecting slow pressure drop in case of small break LOCA. One such technique is the acoustic signal caused by LOCA in small breaks. In boiling water reactors whose primary heat transport is to be driven by natural circulation, small break LOCA detection is important. For prompt action on post small break LOCA, steam leak detection system is developed to detect any leak inside the reactor vault. The detection technique is reliable and plays a very important role in ensuring safety of the reactor. Methodology developed for steam leak detection is discussed in present paper. The methods to locate the leak is also developed and discussed in present paper which is based on analysis of the signal.     

Natural convection boundary layer flow of nanofluids around different stations of the sphere and into the plume above the sphere

The main intent of the present study is to investigate the natural convection boundary layer flow of nanofluids around different stations of the sphere and eruption of the fluid from the boundary layer in to the plume above the sphere. It is pertinent to point out that in this study heated sphere is treated as point source. The system of transport boundary layer equations is based on the effects of Brownian motion and thermophoresis. The system of dimensioned boundary layer equations is transformed into nondimensional form. Later, the nondimensional form of the mathematical model is solved numerically by using implicit finite difference method. The solution of the problem depends on a controlling parameters Prandtl number P_r, Lewis number , thermophoresis parameter , and Brownian motion parameter . Particularly, it is observed that for Lewis number , Prandtl number P_r, Brownian motion parameter , and thermophoresis parameter the velocity profile is maximum at station and minimum at station . On the other hand temperature distribution is uniform at each station around the sphere and slightly reduced for . It is also observed that nanoparticles concentration is maximum at station and minimum at station We also established the result that with the increase of skin friction is reduced while the heat and mass flux are increased in the plume region‐III.     

Preparation and characterization of rare earth orthoborates, LnBO3 (Ln = Tb, La, Pr, Nd, Sm, Eu, Gd, Dy, Y) and LaBO3:Gd, Tb, Eu by metathesis reaction: ESR of LaBO3:Gd and luminescence of LaBO3:Tb, Eu

Lanthanide orthoborates of composition LnBO₃ (Ln = Tb, La, Pr, Nd, Sm, Eu, Gd, Dy, Y) and LaBO₃:Gd, Tb, Eu have been prepared by metathesis reaction. This method provides a convenient route for the synthesis of orthoborates and its solid solutions at low temperatures. Powder X-ray diffraction and FT-IR spectroscopy were used to characterize these borates. Rare earth borates, (LnBO₃) are isomorphous with different forms of CaCO₃ depending on the radius of rare earth ion. LaBO₃, LaBO₃:Gd, Tb, Eu, PrBO₃, NdBO₃ crystallized in aragonite structure, SmBO₃ crystallized in H-form and TbBO₃, EuBO₃, GdBO₃, DyBO₃, YBO₃ crystallized in vaterite structure. The structural analysis of TbBO₃ was carried out. The morphology of these borates was obtained from Scanning electron microscopy. Spin-Hamiltonian parameters for Gd³⁺ are deduced from room temperature electron spin resonance spectrum of LaBO₃:Gd. The luminescence of LaBO₃:Tb, Eu gave characteristics peaks corresponding to Tb³⁺, Eu³⁺ respectively.     

Electrical conduction mechanism in plasma polymerized 1-Benzyl-2-methylimidazole thin films under static electric field

The electrical properties of alternating current plasma polymerized 1-Benzyl-2-methylimidazole (PPBMI) thin films were investigated to determine the dominant carrier transport mechanism under static electric field. Fourier transform infrared (FTIR) spectroscopy was employed for structural analysis of the monomer and that of the PPBMI. The FTIR analyses demonstrate that the chemical structure of PPBMI thin films is changed to some extent from that of the monomer. Current density-voltage characteristics were studied over the temperature range from 300 to 423 K for PPBMI thin films of thicknesses 100, 150, 200 and 250 nm in Al/PPBMI/Al sandwich configuration. It is revealed that the dominant conduction mechanism in PPBMI thin films is space charge limited conduction. The activation energy for the conduction mechanism is found to be 0.43 eV. Carrier mobility, free carrier density and trap density are found to be 1.48 × 10^− 18 to 6.35 × 10^− 18 m² V^− 1 s^− 1, 1.59 × 10²³ to 5.85 × 10²³ m^− 3 and 2.50 × 10²⁴ to 5.00 × 10²³ m^− 3, respectively.     

Synthesis and luminescent characteristics of yellow emitting GdSr2AlO5:Ce phosphor for blue light based white LED

A series of Ce³⁺ ions doped GdSr₂AlO₅ (GSA) phosphors were synthesized by a citric acid based sol–gel method. The X-ray diffraction patterns confirmed their tetragonal structure after the samples were annealed at 1300 °C, and the scanning electron microscope image showed the closely packed particles. The excitation spectra revealed that the GSA phosphor effectively excited with blue light of 442 nm due to the 4f¹→5d¹ transition and exhibited yellow emission corresponding to the 5d¹→4f¹ transition of Ce³⁺ ions. The optimum doping concentration of Ce³⁺ ions was 5 mol% and the critical distance was calculated to be ~17 Å. White LEDs were fabricated by combining blue LED (465 nm) chip with Ce³⁺:GSA phosphor. The CIE chromaticity coordinates (0.34, 0.31) provide their emission potentiality in the white light region.     

Vapour Phase Alkylation of Naphthalene over Lanthana Modified Zeolites

Lanthanum oxide impregnated large-pore zeolite catalysts were prepared. The catalysts were characterized by XRD （X-ray diffraction）, PSA （particle size analysis）, TPD （temperature programmed desorption） and SEM （scanning electron microscope）. The performances of the catalysts were investigated using the alkylation reaction of naphthalene with methanol. Under comparable conditions, the La-impregnated β-zeolite catalyst showed the highest catalytic activity among all the catalysts tested. The lower reaction temperature is favorable for the formation of 2,6-dimethyl naphthalene.     

Pollution studies of River Khan (INDORE) India—I. Biological assessment of pollution

Pollution studies of the River Khan, Indore (India) have been made, with an emphasis on the biological assessment of water quality. The study covers a critical analysis and testing of various European methods for the biological monitoring of water pollution, under the Indian conditions in the River Khan. The river has been divided into different zones of pollution. The biological data have been correlated with the chemical data, and the practical implications of the European saprobity system, under the Indian conditions have been discussed. The importance of benthic macro-invertebrates in the assessment of water quality in the river has also been discussed.