Enhanced Room Temperature Coefficient of Resistance and Magneto-resistance of Ag-added La0.7Ca0.3-xBaxMnO3 Composites

In this paper we report an enhanced temperature coefficient of resistance (TCR) close to room temperature in La0.7Ca0.3-xBaxMnO3 + Agy (x = 0.10, 0.15 and y = 0.0 to 0.40) (LCBMO+Ag) composite manganites. The observed enhancement of TCR is attributed to the grain growth and opening of new conducting channels in the composites. Ag addition has also been found to enhance intra-granular magneto-resistance. Inter-granular MR, however, is seen to decrease with Ag addition. The enhanced TCR and MR at / near room temperature open up the possibility of the use of such materials as infrared bolometric and magnetic field sensors respectively.Comment: 22 pages of Text + Figs:comments/suggestions([email protected]

Growth of dense CNT on the multilayer graphene film by the microwave plasma enhanced chemical vapor deposition technique and their field emission properties

Catalyst assisted carbon nanotubes (CNTs) were grown on multilayer graphene (MLG) on copper and silicon substrates by the microwave plasma enhanced chemical vapor deposition technique. The transmission of the MLG was found to vary between 82 to 91.8% with the increase of deposition time. Scanning electron microscopy depicted that the MLG film survived at the deposition condition of CNTs with the appearance of the damaged structure due to the plasma. Growth of CNTs was controlled by adjusting the flow rates of methane gas. The density of carbon nanotubes was observed to increase with a higher supply of methane gas. It was observed that the field emission properties were improved with the increased density of CNTs on MLG. The lowest turn-on field was found to be 1.6 V mu m(-1) 1 accompanied with the highest current density of 2.8 mA cm(-2) for the CNTs with the highest density. The findings suggested that the field emission properties can be tuned by changing the density of CNTs

Electrical Properties of lead free ceremics Na1−XKxNbO3, at x=0.305.

By solid state reaction method, ceramic pellets of Na0.695K0.305NbO3 have been prepared. X-ray- diffraction, Piezo properties, scanning electron microscope, and temperature dependence of dielectric constant and loss tangent of the prepared samples have been studied. It has been observed that, at the transition temperature, dielectric constant peak shifts to lower temperature, and the dielectric constant and loss tangent peak heights decrease, with  increasing frequency, and show three structural phase transitions

Dielectric properties of Na1−xKxNbO3, near x = 0.475 morphotropic phase region

11-17Sodium-potassium niobate (Na1−xKxNbO3) ceramic pellets, with x = 0.465, 0.470, 0.475, 0.480 and 0.485, were prepared by solid state reaction method with double sintering. With varying composition (x), the dielectric properties, X-ray diffraction peaks shifting pattern, in this system. Among the prepared compositions, a break in the X-ray diffraction peaks shifting tendency; minimum dielectric constant, loss tangent and dielectric conductivity indicate a morphotropic phase transition type behavior, at the composition with x = 0.475

Electrical Properties of lead free ceremics Na1−XKxNbO3, at x=0.305.

783-786By solid state reaction method, ceramic pellets of Na0.695K0.305NbO3 have been prepared. X-ray- diffraction, Piezo properties, scanning electron microscope, and temperature dependence of dielectric constant and loss tangent of the prepared samples have been studied. It has been observed that, at the transition temperature, dielectric constant peak shifts to lower temperature, and the dielectric constant and loss tangent peak heights decrease, with increasing frequency, and show three structural phase transitions

Piezoelectric Properties of Ta (≤ 5 (mole)%) Doped in Na0.685K0.315NbO3

To explore the piezoelectric potential of Ta doping on the MPB- like composition Na0.685K0.315NbO3, ceramic pellets of Na0.685K0.315Nb1-yTayO3 (y ≤ 0.05) were arranged by solid-state reaction method. For piezoelectric measurements, sintered pellets were electroded, in parallel capacitor configuration, with silver coating deposited by direct current (dc) magnetron sputtering of a silver target. Polarization and piezoelectric parameters were measured using a ferroelectric (PE- loop tracer) and piezo- meter (AixACCT Systems, GmbH). Composition (y) variation of remnant polarization, coercive field, converse piezoelectric coefficient (d*33), and polarization current measurements were carried out in the prepared compositions. The remnant polarization (Pr) is 18.439 μC/cm2 with a coercive field (Ec) of 8 kV/cm for NKNT single crystals. d*33 was observed 300.76 pm/V for y = 0.04 at the applied field of 22kV/cm

Structural and Piezoelectric Properties of (Ba1-xCaxZr0.1Ti0.9)O3 Ceramics, Near Morphotropic Phase Boundary (0.140 ≤ x ≤ 0.160)

111-116Ceramic pellet samples of (Ba1-xCaxZr1-yTiy)O3 (x = 0.140- 0.160, y = 0.9), were prepared using the conventional solidstate reaction method followed by double sintering. Structural and piezoelectric measurements of the prepared compositions were carried out at room temperature. For the compositions with x ≤ 0.150, the converse piezoelectric constant (d33*), strain (%), coercive field (Ec) and remnant polarization (Pr), were found increasing with x, which were found anomalously to decrease with further increase in x above 0.150. Among the prepared compositions, maximum value of d33* was found 342 pm/V, for the samples with x = 0.150. The measured maximum values of strain (%), piezoelectric constant (d33*) and break in XRD peak shifting patterns of the prepared samples indicate composition dependent piezoelectric properties, showing morphotropic- like phase boundary (MPB), near x = 0.150 composition. The prepared compositions of lead- free BCZT ceramics will extend the possibilities to use this compound in the field of piezoelectric sensors

Nonlinear regression techniques for analysis of onion (Allium cepa) production in India

India occupies second position in the production of onion in the world. Keeping in view the importance of this crop, the present study has been undertaken to find out the growth in production of onion and discusses the application of nonlinear models, viz. Gompertz, Logistic, MMF, Richards and Weibull models, which measure the growth. Time series data on onion production in major growing states; viz. Andhra Pradesh, Gujarat, Karnataka, Maharashtra, Uttar Pradesh, and all India from 1990–91 to 2009–10 has been utilized for the present study. From a realistic point of view, the relationships among variables in agricultural and horticultural sciences are non-linear in nature. Non-linear models are very popularly used to estimate the trend in various fields such as population studies and animal growth where growth is not symmetrical about the point of inflection. The results showed that Logistic and Gompertz models faired marginally better than Weibull and MMF model