Electron Donating Property and Catalytic Activity of Perovskite-type Mixed Oxides (ABO3 ) Consisting of Rare Earth and 3d Transition Metals

The catalytic activity of Perovskite-type mixed oxides (LaCo03 . PrCo03 and SmCo03 ) for the reduction of cyclohexanone to cyclohexanol with 2-propanol (Meerwein-Ponndorf-Verley reduction) has been studied. The data have been correlated with the surface electron donor properties of these mixed oxides.

Nanosecond optical limiting response of sandwich-type neodymium dyphthalocyanine in a co-polymer host

The nanosecond optical limiting characteristics of sandwich-type neodymium diphthalocyanine in a co-polymer matrix of polymethyl methacrylate (PMMA) and methyl-2-cyanoacrylate have been studied for the first time. The measurements were performed using 9 ns laser pulses generated from a frequency-doubled Nd:YAG laser at 532 nm wavelength. The optical limiting performance of neodymium diphthalocyanine in co-polymer host was studied at different linear transmission. Laser damage threshold was also measured for the doped and undoped co-polymer samples. The optical limiting response is attributed to reverse saturable absorption which is due to excited-state absorption.

Growth and characterisation of p-type delafossite transparent conducting thin films for heterojunction applications

In the present studies, various copper delafossite materials viz; CuAlO2, CuGaO2, CuFeO2 , CuGa1-xFexO2, CuYO2 and CuCaxY1-xO2 were synthesised by solid state reaction technique. These copper delafossite materials were grown in thin film form by rf magnetron sputtering technique. In general copper delafossites exhibit good optical transparency. The conductivity of the CuYO2 could be improved by Ca doping or by oxygen intercalation by annealing the film in oxygen atmosphere. It has so far been impossible to improve the p-type conductivity of CuGaO2 significantly by doping Mg or Ca on the Ga site. The ptype conductivity is presumed to be due to oxygen doping or Cu Vacancies [6]. Reports in literature show, oxygen intercalation or divalent ion doping on Ga site is not possible for CuGaO2 thin films to improve the p-type conductivity. Sintered powder and crystals of CuFeO2 have been reported as the materials having the highest p-type conductivity [14, 15] among the copper and silver delafossites. However the CuFeO2 films are found to be less transparent in the visible region compared to CuGaO2. Hence in the present work, the solid solution between the CuGaO2 and CuFeO2 was effected by solid state reaction, varying the Fe content. The CuGa1-xFexO2 with Fe content, x=0.5 shows an increase in conductivity by two orders, compared to CuGaO2 but the transparency is only about 50% in the visible region which is less than that of CuGaO2 The synthesis of α−AgGaO2 was carried out by two step process which involves the synthesis of β-AgGaO2 by ion exchange reaction followed by the hydrothermal conversion of the β-AgGaO2 into α-AgGaO2. The trace amount of Ag has been reduced substantially in the two step synthesis compared to the direct hydrothermal synthesis. Thin films of α-AgGaO2 were prepared on silicon and Al2O3 substrates by pulsed laser deposition. These studies indicate the possibility of using this material as p-type material in thin film form for transparent electronics. The room temperature conductivity of α-AgGaO2 was measured as 3.17 x 10-4 Scm-1and the optical band gap was estimated as 4.12 eV. A transparent p-n junction thin film diode on glass substrate was fabricated using p-type α-AgGaO2 and n-ZnO.AgCoO2 thin films with 50% transparency in the visible region were deposited on single crystalline Al2O3 and amorphous silica substrates by RF magnetron sputtering and p type conductivity of AgCoO2 was demonstrated by fabricating transparent p-n junction diode with AgCoO2 as p-side and ZnO: Al as n-side using sputtering. The junction thus obtained was found to be rectifying with a forward to reverse current of about 10 at an applied voltage of 3 V.The present study shows that silver delafossite thin films with p-type conductivity can be used for the fabrication of active devices for transparent electronics applications.

Development of p-type transparent semiconducting oxides for thin film transistor applications

Semiconductor physics has developed significantly in the field of re- search and industry in the past few decades due to it’s numerous practical applications. One of the relevant fields of current interest in material science is the fundamental aspects and applications of semi- conducting transparent thin films. Transparent conductors show the properties of transparency and conductivity simultaneously. As far as the band structure is concerned, the combination of the these two properties in the same material is contradictory. Generally a trans- parent material is an insulator having completely filled valence and empty conduction bands. Metallic conductivity come out when the Fermi level lies within a band with a large density of states to provide high carrier concentration. Effective transparent conductors must nec- essarily represent a compromise between a better transmission within the visible spectral range and a controlled but useful electrical con- ductivity [1–6]. Generally oxides like In2O3, SnO2, ZnO, CdO etc, show such a combination. These materials without any doping are insulators with optical band gap of about 3 eV. To become a trans- parent conductor, these materials must be degenerately doped to lift the Fermi level up into the conduction band. Degenerate doping pro- vides high mobility of extra carriers and low optical absorption. The increase in conductivity involves an increase in either carrier concen- tration or mobility. Increase in carrier concentration will enhance the absorption in the visible region while increase in mobility has no re- verse effect on optical properties. Therefore the focus of research for new transparent conducting oxide (TCO) materials is on developing materials with higher carrier mobilities.

Raman and FTIR studies of the structural aspects of Nasicon-type crystals; AFeTi(PO4)3 [A ¼ Ca, Cd]

Raman and FTIR spectra of CaFeTi(PO4)3 and CdFeTi(PO4)3 are recorded and analyzed. The observed bands are assigned in terms of vibrations of TiO6 octahedra and PO4 tetrahedra. The symmetry of TiO6 octrahedra and PO4 tetrahedra is lowered from their free ion symmetry. The presence of Fe3+ ion disrupts the Ti–O–P–O–Ti chain and leads to the distortion of TiO6 octrahedra and PO4 tetrahedra. The PO4 3 tetrahedra in both crystals are linearly distorted. The covalency bonding factor of PO4 3 polyanion of both the crystals are calculated from the Raman spectra and compared to that of other Nasicon-type systems. The numerical values of covalency bonding factor indicates that there is a reduction in redox energy and cell voltage and is attributed to strong covalency of PO4 3 polyanionin

FT-IR and FT-Raman study of Nasicon type phosphates, ASnFe(PO4)3 [A=Na2, Ca, Cd]

FT-Raman and FT-IR spectra of ASnFe(PO4)3 [A=Na2, Ca, Cd] were recorded and analyzed. The bands were assigned in terms of the vibrational group frequencies of SnO6 octahedral and PO4 tetrahedral. The spectral analysis shows that the symmetry of corner shared octahedral (SnO6) and the tetrahedral (PO4) are lowered from their free ion symmetry state. The presence of Fe3+ ions disrupts the S–N–O–S–N chain in the structure. This causes distortion of SnO6 and PO4 in the structure of all the compounds. Also it is seen that there are two distinct PO4 tetrahedra of different P–O bond lengths. One of these tetrahedra is linearly distorted in all the title compounds. The PO4 frequencies and bond lengths are calculated theoretically and are in agreement with the experimental values. The presence of PO4 polyanion in the structure can reduce the redox energy and hence reduce the metal oxygen covalency strength in the structure

Significance Of Product Type And Brand In The Purchasing Behaviour Of Cattle Feeds: An Empirical Study In Kerala

Cattle feed industry is a major segment of animal feed industry. This industry is gradually evolving into an organized sector and the feed manufactures are increasingly using modern and sophisticated methods that seek to incorporate best global practices. This industry has got high potential for growth in India, given the fact that the country is the world’s leading producer of milk and its production is expected to grow at a compounded annual growth rate of 4 per cent. Besides, the concept of branded cattle feed as a packaged commodity is fast gaining popularity in rural India. There can be a positive change in the demand for cattle feed because of factors like (i) shrinkage of open land for cattle grazing, urbanization and resultant shortage of conventionally used cattle feeds, and (ii) introduction of high yield cattle requires specialized feeds. Earlier research studies done by the present authors have revealed the significant growth prospects of the branded cattle feed industry, the feed consumption pattern and the relatively high share of branded feeds, feed consumption pattern based on product types (like, pellet and mash), composition of cattle feed market and the relatively large shares of Kerala Feeds Ltd. (KFL) and Kerala Solvent Extractions Ltd. (KSE) brands, the major factors influencing the purchasing decisions etc. As a continuation of the earlier studies, this study makes a closer look into the significance of product types in the buyer behavior, level of awareness about the brand and its implications on purchasing decisions, and the brandshifting behavior and its determinants

Analysis of some Stochastic models in inventories and Queues

The thesis entitled Analysis of Some Stochastic Models in Inventories and Queues. This thesis is devoted to the study of some stochastic models in Inventories and Queues which are physically realizable, though complex. It contains a detailed analysis of the basic stochastic processes underlying these models. In this thesis, (s,S) inventory systems with nonidentically distributed interarrival demand times and random lead times, state dependent demands, varying ordering levels and perishable commodities with exponential life times have been studied. The queueing system of the type Ek/Ga,b/l with server vacations, service systems with single and batch services, queueing system with phase type arrival and service processes and finite capacity M/G/l queue when server going for vacation after serving a random number of customers are also analysed. The analogy between the queueing systems and inventory systems could be exploited in solving certain models. In vacation models, one important result is the stochastic decomposition property of the system size or waiting time. One can think of extending this to the transient case. In inventory theory, one can extend the present study to the case of multi-item, multi-echelon problems. The study of perishable inventory problem when the commodities have a general life time distribution would be a quite interesting problem. The analogy between the queueing systems and inventory systems could be exploited in solving certain models.