http://nopr.niscair.res.in/handle/123456789/11593 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/11606 Title: Effect of structural disorder on electrical and magneto transport of La_0.5Pr_0.2R_0.3MnO₃ (R = Sr and Ba) manganite films <br/> <br/>Authors: Markna, J H; Solanki, P S; Khachar, U D; Thaker, C M; Rana, D S; Kuberkar, D G <br/> <br/>Abstract: The manganite thin films La_0.5Pr_0.2R_0.3MnO₃ (R = Sr²⁺ and Ba²⁺) have been studied to understand the effect of A-site cationic size disorder (σ_A²) on their electrical and magneto transport properties. Epitaxial thin films of La_0.5Pr_0.2Sr_0.3MnO₃ (LPSMO) and La_0.5Pr_0.2Ba_0.3MnO₃ (LPBMO) were synthesized using Pulsed Laser Deposition (PLD) technique with desirable thicknesses of 150 nm. In the present paper, it is shown, how Sr⁺² and Ba⁺² substitution at La-site leads to half-metallicity in LPSMO and low temperature resistivity minima in LPBMO films, respectively. It is observed that the resistivity and high field magneto resistance (HFMR) increase to ~ 55% in LPSMO and ~ 95% in LPBMO films with increasing size disorder. The increase in cation size disorder in LPBMO as compared to LPSMO, results in high values of positive and negative temperature coefficient of resistance (TCR) ~ 59.8%K⁻¹ and −55.1% K⁻¹, respectively. <br/> <br/>Page(s): 354-359 http://nopr.niscair.res.in/handle/123456789/11605 Title: Dielectric and electrical properties of K_1−xNa_xNbO₃ system <br/> <br/>Authors: Uniyal, Manish; Bhatt, S C <br/> <br/>Abstract: Dielectric and electrical properties of K_1−xNa_xNbO₃ (<i>x</i>=0, 0.2, 0.4) ceramics have been investigated in the temperature range 35-250°C at different frequencies in the range 0.1-1 MHz. The samples have been prepared by the conventional solid-state reaction method and sintering process. It is observed that dielectric constant, loss tangent and electrical conductivity increase with increasing temperature. Near the transition temperature, dielectric constant, loss tangent and electrical conductivity of these samples show anomalous behaviour. All the prepared samples show orthorhombic structure at room temperature. <br/> <br/>Page(s): 350-353 http://nopr.niscair.res.in/handle/123456789/11604 Title: Prediction of effective thermal conductivity of cellular and polymer composites <br/> <br/>Authors: Singh, Ramvir; Sharma, P K; Bhoopal, R S; Verma, L S <br/> <br/>Abstract: Theoretical expression has been developed to predict effective thermal conductivity (ETC) of cellular and polymer composites considering random flow of heat flux lines. The concept of averaging temperature field within different phases has been used. For heterogeneous materials, the parameter <i style="">F</i> has been introduced in place of physical porosity. Due to the randomness of the flux lines in heterogeneous materials, the laws of statistical mechanics have been used to derive the expression in terms of the ratio of thermal conductivity of the constituents and the physical porosity. Expression so obtained for <i style="">F</i> is used in the model and it has been found that the predicted results of effective thermal conductivity are quite close to the experimental values. A comparison of the proposed relation with different models has also been made. <br/> <br/>Page(s): 344-349 http://nopr.niscair.res.in/handle/123456789/11603 Title: Synthesis, growth and characterization of copper mercury thiocyanate crystal <br/> <br/>Authors: Vijayabhaskarana, B; Arivazhagan, M; Raja, C Ramachandra <br/> <br/>Abstract: Synthesis and growth of nonlinear optical copper mercury thiocyanate, CuHg(SCN)₄ (CMTC) single crystals have been successfully carried out by slow evaporation technique using water and ethanol as solvents with dimensions up to 12´8´5 mm³. The grown single crystals have been studied by different characterization techniques in order to know their suitability for various applications. The lattice parameters of the crystal have been obtained by single crystal X-ray diffraction analysis. The presence of functional groups have been identified using FTIR analysis. The thermal stability and thermal decomposition of CMTC crystals have been &nbsp;investigated by using thermo gravimetric analysis and differential thermal analysis. The CMTC crystal exhibits good physio-chemical stability up to 253.8°C. The optical transparency of the grown crystal has been studied by UV-vis-NIR analysis. The lower cutoff wavelength of CMTC crystal occurs at 390 nm and has been discovered as a non linear optical crystal material. The relative second harmonic generation efficiency of the CMTC crystal has been tested by Kurtz - Perry powder technique. <br/> <br/>Page(s): 340-343