Low temperature magnetic and magnetocaloric studies in YCr0.85Mn0.15O3 ceramic

We have investigated low temperature magnetic and magnetocaloric properties of manganese (Mn) doped YCr0.85Mn0.15O3 (YCMO) polycrystalline compound, synthesized via solid state reaction route. The lattice volume was found to increase in comparison to that of pristine YCrO3 (YCO) compound. On the other hand, the paramagnetic-antiferromagnetic Néel temperature (TN ∼ 132 K) was found to be lower than that for YCO ceramic. On cooling below TN, under field cooled (FC) mode with an applied magnetic field of 0.02 T, magnetization flipped the polarity from positive to negative at Tcomp = 62 K. Furthermore, the magnetization switching temperature, defined as compensation temperature, exhibited field dependency and decreased with increasing field. Besides, the magnetization reversal phenomenon disappeared under higher applied magnetic field values. For the first time, the magnetocaloric effect for this compound was measured near 36 K through the parameters like magnetic entropy change (−ΔS) = ∼0.186 J kg−1 K−1 and the relative cooling power (RCP) ∼ 6.65 J kg−1, under an applied field of 5 T.publishe

Structural, electrical, optical and magnetic properties of SmCrO3 chromites: influence of Gd and Mn co-doping

Impact of co-doping of Gadolinium (Gd) and Manganese (Mn) ions on the structural, electrical, optical and magnetic properties of SmCrO3 (SCO) orthochromite compound has been systematically investigated for the first time. The lattice volume expanded with only Mn substitution whereas it shrinks in the co-doped compounds. The tolerance factor decreased while the orthorhombic distortion was found to increase with co-doping. Tilt angle, θ[101] (ο) increased in the co-doped compounds. On the contrary, ∅[010] (ο) initially decreased and then increased. The increased orthorhombic distortion with co-doping also influenced the Raman modes. The electrical resistivity got enhanced in the co-doped samples and its behavior was explained based on Mott's variable range hopping model. Hopping energy and mean hopping distance have also been estimated for the co-doped compounds. The optical bandgap of pristine SCO compound was observed to vary with co-doping, signifying the potential applications of these compounds as photocatalyst. Two compensation temperatures (defined as a temperature where the magnetization changes polarity) were noticed in co-doped compounds. The magnetization reversal was observed in all the co-doped compounds under lower applied magnetic field. The low temperature magnetocaloric effect got enhanced significantly with increasing co-doping content implying the usefulness of these compounds as low temperature refrigerant materials.publishe

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

Composition-Dependent Dielectric and Piezoelectric Properties of Na1-zKzNbO3 Ceramics

Sodium potassium niobate, Na1-zKzNbO3, is a ceramic material that exhibits dielectric and piezoelectric properties, which can be tuned by changing the composition of the material. The dielectric properties of Na1-zKzNbO3 ceramics are characterized by a high dielectric constant and low loss, which makes them useful for applications in capacitors, filters, and resonators. Pellets of Na1-zKzNbO3 (0.120 ≤ z ≤ 0.210) were prepared by the solid-state reaction technique. The structural and morphological study was carried out on the prepared compositions at room temperature (RT). A Piezoelectric indirect constant (d33*) was obtained for the prepared compositions. Additionally, dielectric measurements were performed at frequencies 10-1000 kHz, from ambient temperature to 500 °C. For the prepared compositions with z = 0.175, a break in the XRD peak shifting patterns was observed, and the average grain size was calculated at 2.044 ± 0.3 µm. Also, the maximum indirect piezoelectric constant (d33*) was observed for z = 0.175 among the prepared compositions. For the prepared compositions, compositions with z = 0.140 showed the highest dielectric constant (peak value 1486, 385 °C). Among the prepared samples, dielectric constant (ε), loss tangent (tan δ) and electric conductivity (σ) were found to be minimum for the composition with z = 0.175 at all the measured frequencies. Anomalous dielectric, piezoelectric and structural properties are evident for the samples with z = 0.175 among the prepared samples. Overall, the composition-dependent dielectric and piezoelectric properties of Na1-zKzNbO3 ceramics make them promising materials for use in various electronic and sensing applications where high-performance dielectric and piezoelectric materials are required

Role of renewable energy sources in environmental protection: A review

Renewable technologies are considered as clean sources of energy and optimal use of these resources minimize environmental impacts, produce minimum secondary wastes and are sustainable based on current and future economic and social societal needs. Sun is the source of all energies. The primary forms of solar energy are heat and light. Sunlight and heat are transformed and absorbed by the environment in a multitude of ways. Some of these transformations result in renewable energy flows such as biomass and wind energy. Renewable energy technologies provide an excellent opportunity for mitigation of greenhouse gas emission and reducing global warming through substituting conventional energy sources. In this article a review has been done on scope of CO2 mitigation through solar cooker, water heater, dryer, biofuel, improved cookstoves and by hydrogen.Greenhouse gases CO2 mitigation Sustainable development Renewable energy sources

Changes in ecological conditions may influence intraguild competition: inferring interaction patterns of snow leopard with co-predators

Background Large-scale changes in habitat conditions due to human modifications and climate change require management practices to consider how species communities can alter amidst these changes. Understanding species interactions across the gradient of space, anthropogenic pressure, and season provide the opportunity to anticipate possible dynamics in the changing scenarios. We studied the interspecific interactions of carnivore species in a high-altitude ecosystem over seasonal (summer and winter) and resource gradients (livestock grazing) to assess the impact of changing abiotic and biotic settings on coexistence. Methods The study was conducted in the Upper Bhagirathi basin, Western Himalaya, India. We analyzed around 4 years of camera trap monitoring data to understand seasonal spatial and temporal interactions of the snow leopard with common leopard and woolly wolf were assessed in the greater and trans-Himalayan habitats, respectively. We used two species occupancy models to assess spatial interactions, and circadian activity patterns were used to assess seasonal temporal overlap amongst carnivores. In addition, we examined scats to understand the commonalities in prey selection. Results The result showed that although snow leopard and wolves depend on the same limited prey species and show high temporal overlap, habitat heterogeneity and differential habitat use facilitate co-occurrence between these two predators. Snow leopard and common leopard were spatially independent in the summer. Conversely, the common leopard negatively influences the space use of snow leopard in the winter. Limited prey resources (lack of livestock), restricted space (due to snow cover), and similar activity patterns in winter might result in strong competition, causing these species to avoid each other on a spatial scale. The study showed that in addition to species traits and size, ecological settings also play a significant role in deciding the intensity of competition between large carnivores. Climate change and habitat shifts are predicted to increase the spatial overlap between snow leopard and co-predators in the future. In such scenarios, wolves and snow leopards may coexist in a topographically diverse environment, provided sufficient prey are available. However, shifts in tree line might lead to severe competition between common leopards and snow leopards, which could be detrimental to the latter. Further monitoring of resource use across abiotic and biotic environments may improve our understanding of how changing ecological conditions can affect resource partitioning between snow leopards and predators

Low-Temperature Magnetic and Magnetocaloric Properties of Manganese-Substituted Gd0.5Er0.5CrO3 Orthochromites

Rare-earth chromites have been envisioned to replace gas-based refrigeration technology because of their promising magnetocaloric properties at low temperatures, especially in the liquid helium temperature range. Here, we report the low-temperature magnetic and magnetocaloric properties of Gd0.5Er0.5Cr1−xMnxO3 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) rare-earth orthochromites. The Néel transition temperature (TN) was suppressed from 144 K for Gd0.5Er0.5CrO3 to 66 K for the Gd0.5Er0.5Cr0.5Mn0.5O3 compound. Furthermore, magnetization reversal was observed in the magnetization versus temperature behavior of the Gd0.5Er0.5Cr0.6Mn0.4O3 and Gd0.5Er0.5Cr0.5Mn0.5O3 compounds at 100 Oe applied magnetic field. The magnetic entropy change (−∆S) value varied from 16.74 J/kg-K to 7.46 J/kg-K, whereas the relative cooling power (RCP) ranged from 375.94 J/kg to 220.22 J/kg with a Mn ion concentration at 5 T field and around 7.5 K temperature. The experimental results were substantiated by a theoretical model. The present values of the magnetocaloric effect are higher than those of many undoped chromites, manganites and molecular magnets in the liquid helium temperature range