@article { ISI:000239359100012, title = {Dielectric properties of BaTiO3 ceramics prepared from powders with bimodal distribution}, journal = {Journal of Industrial and Engineering Chemistry}, volume = {12}, number = {4}, year = {2006}, month = {JUL}, pages = {584-588}, publisher = {KOREAN SOC INDUSTRIAL ENGINEERING CHEMISTRY}, type = {Article}, address = {A-803 TWIN BLDG, 275-3, YANGJAE-DONG, SEOCHO-KU, SEOUL 137-130, SOUTH KOREA}, abstract = {

BaTiO3 (BT) powders having bimodal distribution were synthesized successfully through a simple classical solid-state reaction route using cheap BaCO3 and TiO2 as starting materials. These powders were further processed in the form of green pellets to obtain dense BT ceramics having densities of similar to 94 similar to 96 \% after sintering in air at 1350 and 1400 degrees C/4 h in air. The room temperature dielectric constant (epsilon(RT)) of similar to 1500 at 1 KHz frequency was increased to : 10000 at a Curie temperature (T-C) similar to 126 degrees C, showing a very sharp transition from a polar tetragonal to a non-polar cubic structure. The dielectric loss factor (tan 6) was similar to 1.5 \%. SEM studies revealed the presence of dense microstructures having a distribution of smaller grains (size: 2 similar to 3 gm) surrounded by larger grains (\>= 35 mu m). The ferroelectric hysteresis loop measurements on these samples gave values of spontaneous polarization (P-s) of similar to 12.0 mu C/cm(2), a coercive field (E-C) of similar to 2 similar to 2.5 kV/cm, and a dielectric strength (E-b) of similar to 48.0 kV/cm. DC-resistivity as high as 1.5 x 10(9) Omega-cm was obtained in these samples. All these results are quite comparable with reported ferroelectric/dielectric data and are discussed elaborately in this paper.

}, keywords = {BaTiO3, dielectric-ferroelectric properties, Microstructure, Sintering, stoichiometry}, issn = {1226-086X}, author = {Deshpande, S. B. and Potdar, H. S. and Patil, M. M. and Deshpande, V. V. and Khollam, Y. B.} } @article { ISI:000260483400085, title = {Varistor property of SnO2 center dot CoO center dot Ta2O5 ceramic modified by barium and strontium}, journal = {Journal of Alloys and Compounds}, volume = {466}, number = {1-2}, year = {2008}, month = {OCT}, pages = {483-487}, publisher = {ELSEVIER SCIENCE SA}, type = {Article}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

The influence of an alkali earth (Ba/Sr) element in small quantities (\< 1 at.\%) on non-linear electrical properties of 98.5\% SnO2 + 1\% CoO + 0.5\% Ta2O5 (all in at.\%) varistor system has been investigated. The non-linear coefficient increases from 33 to 52 whereas breakdown field strength varies 5025-6050 V cm(-1) for the barium-doped samples. In case of strontium-doped specimens moderate increase in non-linear coefficient but significant increase in breakdown field is observed. It is proposed that due to ionic size misfit, Ba and Sr segregates to grain boundaries thereby modifying their barrier properties. The contribution from grain boundary phase to the electrical property is confirmed by the impedance analysis. (C) 2007 Elsevier B.V. All rights reserved.

}, keywords = {Oxide materials, scanning electron microscopy, Sintering}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2007.11.062}, author = {Dhage, S. R. and Ravi, V. and Yang, O. B.} } @article { ISI:000271542900165, title = {Synthesis and characterization of CoCrxFe2-xO4 nanoparticles}, journal = {Journal of Alloys and Compounds}, volume = {485}, number = {1-2}, year = {2009}, month = {OCT}, pages = {798-801}, publisher = {ELSEVIER SCIENCE SA}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

Spinel-phase nanocrystalline CoCrxFe2-xO4 powders (0.0 \<= x \<= 2.0) were synthesized by citrate-gel precursor method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). transmission electron microscopy (TEM) and infra-red spectroscopy (FT-IR). The XRD and selected-area electron diffraction (SAED) patterns indicated that the synthesized nanoparticles have single-phase spinet structure without the presence of any other impurities. The changes in electrical and magnetic properties of different stiochiometric compositions have also been investigated. It is seen that with increase in chromium contents, the measured magnetic hysteresis loops become narrow with decreasing trend in saturation magnetization. Electrical resistivity indicated that all the compounds are semiconducting nature. (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {Magnetic measurements, Sintering, transmission electron microscopy, X-ray diffraction}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2009.06.087}, author = {Hankare, P. P. and Sankpal, U. B. and Patil, R. P. and Mulla, Imtiaz S. and Lokhande, P. D. and Gajbhiye, N. S.} } @article { ISI:000281175500059, title = {Simple chemical co-precipitation/calcination route for the synthesis of simulated synroc-B and synroc-C powders}, journal = {Materials Chemistry and Physics}, volume = {123}, number = {2-3}, year = {2010}, month = {OCT}, pages = {695-699}, publisher = {ELSEVIER SCIENCE SA}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

A simple chemical co-precipitation/calcination route was developed for the synthesis of simulated synroc-B and synroc-C powders using mostly nitrate salts as starting chemicals and 20\% ammonia solution as precipitant. In this route, a mixed solution containing Al-nitrate, Ca-nitrate, Ba-nitrate, zirconyl nitrate and titanyl nitrate in the molar proportion required for synroc-B is added to dilute ammonia solution to precipitate these cations in the form of their hydroxides at room temperature by maintaining pH approximate to 10.5 during precipitation. Formation of a major fluorite phase with minor amounts of anatase, rutile and hollandite phases is observed in the powder obtained after calcination in air at 750 degrees C. Multiphase crystalline synroc-B matrix containing hollandite, perovskite, zirconolite, and rutile phases is obtained after sintering the heat treated powder in the form of pellets at 1230 degrees C for 4h in air. Similarly, pure synroc-C phases with 14 and 20\% simulated waste loadings were synthesized following the same synthesis protocol. These pre-treated powders with a high surface area of similar to 25 m(2) g(-1) gave sintered ceramics having density of similar to 90\% for 14 and 20\% waste loadings. (C) 2010 Elsevier B.V. All rights reserved.

}, keywords = {Ceramics, Chemical synthesis, Oxides, Sintering}, issn = {0254-0584}, doi = {10.1016/j.matchemphys.2010.05.039}, author = {Potdar, H. S. and Vijayanand, S. and Mohaideen, Kamal Khaja and Patil, K. R. and Joy, Pattayil Alias and Madhavan, R. Raja and Kutty, K. V. G. and Ambashta, Ritu D. and Wattal, P. K.} } @article { ISI:000278744500055, title = {Synthesis and characterization of nanocrystalline zinc substituted nickel ferrites}, journal = {Journal of Alloys and Compounds}, volume = {496}, number = {1-2}, year = {2010}, month = {APR}, pages = {256-260}, publisher = {ELSEVIER SCIENCE SA}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

Nanocrystalline zinc substituted nickel ferrites, Ni(1-x)Zn(x)Fe(2)O(4) (0.0 \<= x \<= 1.0) have been prepared by citrate gel auto-combustion method. The effect of zinc ion content on structural, electrical transport and magnetic properties has been studied. The X-ray diffraction (XRD) pattern revealed that, all the compositions possess single-phase spinel structure. The nano-sized grain structure formation was confirmed by transmission electron microscopy (TEM). The dc electrical resistivity shows the samples are semiconducting in nature. The magnetic measurements showed that the composition Ni(0.6)Zn(0.4)Fe(2)O(4) has maximum saturation magnetization (M(s)) while high coersivity (Hc) for ZnFe(2)O(4). Thermoelectric power measurement study showed that the compounds, with x \<= 0.4 are p-type and for x \> 0.4 behaves n-type conduction mechanism. (C) 2010 Published by Elsevier B.V.

}, keywords = {Electron microscopy, Magnetic, Sintering, X-ray diffraction}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2010.01.009}, author = {Hankare, P. P. and Sankpal, U. B. and Patil, R. P. and Mulla, Imtiaz S. and Sasikala, R. and Tripathi, A. K. and Garadkar, K. M.} } @article { ISI:000313149800004, title = {Enhancement in the magnetostriction of sintered cobalt ferrite by making self-composites from nanocrystalline and bulk powders}, journal = {ACS Applied Materials \& Interfaces}, volume = {4}, number = {12}, year = {2012}, month = {DEC}, pages = {6421-6425}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Sintered polycrystalline cobalt ferrite is a potential magnetostrictive smart material for applications as sensors and actuators. A novel concept of enhancing the magnetostrictive strain of sintered cobalt ferrite by making self-composites from nanosized and bulk powders with different particle sizes of the same material as components is reported. The self-composites give higher magnetostriction coefficient and strain derivative when compared to the sintered products obtained from the individual powders. The individual components give a maximum magnetostriction up to similar to 310 ppm, whereas up to similar to 370 ppm is obtained for a two-component system consisting of powders of two different sizes. On the other hand, a three-component self-composite made from starting powders of 3 nm, 40 nm and \>1 mu m give very high magnetostriction of similar to 400 ppm at 800 kA/m, suitable for making devices.

}, keywords = {Cobalt ferrite, Magnetostriction, Nanocrystalline, self-composite, Sintering}, issn = {1944-8244}, doi = {10.1021/am302053q}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article { ISI:000329554400013, title = {Studies on the effect of sintering conditions on the magnetostriction characteristics of cobalt ferrite derived from nanocrystalline powders}, journal = {Journal of the European Ceramic Society}, volume = {34}, number = {3}, year = {2014}, month = {MAR}, pages = {677-686}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

The effect of sintering conditions on the magnetostriction characteristics of sintered cobalt ferrite derived from nanocrystalline powders is studied. It is observed that the magnetostriction coefficient as well as the slope of the magnetostriction as a function of field depends on the microstructure of the sintered product. There is a direct correlation between the magnetostriction characteristics and density as well as porosity of the sintered products. Intragranular pores are found to be strongly influencing the magnetostriction characteristics. Similarly, correlation is found between the magnetostriction parameters and the Curie temperature, indicating the role of cation distribution which affects the magnetic anisotropy. Sintering the compacts made from nanocrystalline powders at 1450 degrees C for a very short duration is found to give high values of magnetostriction coefficient. However, higher values of magnetostriction at low magnetic fields are obtained for samples sintered at lower temperatures for longer duration and having relatively lower density. (C) 2013 Elsevier Ltd. All rights reserved.

}, keywords = {Cobalt ferrite, Magnetostriction, Microstructure, Nanocrystalline, Sintering}, issn = {0955-2219}, doi = {10.1016/j.jeurceramsoc.2013.09.018}, author = {Mohaideen, Kamal Khaja and Joy, Pattayil Alias} } @article { ISI:000354137000018, title = {Encapsulation of ultra small metal clusters in silica: evolution of the concept of nanoreactors and the case of Ag-Pd@SiO2 alloy catalyst}, journal = {Catalysis Today}, volume = {251}, year = {2015}, note = {7th Tokyo Conference on Advanced Catalytic Science and Technology (TOCAT), Kyoto, JAPAN, JUN 01-06, 2014}, month = {AUG}, pages = {114-120}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The concept of encapsulation of ultra small clusters within silica evolved as a means to address the sintering of active metal nanoparticles and subsequent deactivation observed in supported noble metal catalysts. It is hypothesised that sintering, which mainly occurs due to mobility of metal species on the support surfaces, can be minimised if the growth and movement of metal nanoparticles are constrained. First, nanoparticles are isolated inside 1D channels in 2D mesoporous compounds and the idea develops to complete encapsulation of thiol protected ultra small nanoclusters in silica spheres. Sintering is better controlled in the latter due to the confined space for growth of nanoparticles. Access of reactant molecules to the active metal surfaces also is ensured by porosity created in the silica matrix forming the basis of the concept of nanoreactors. In this paper, we elaborate on the evolution of this concept from our earlier work on highly sinter resistant silica encapsulated Au, Pd and Au-Pd alloys to the present system of Ag-Pd alloy encapsulated in silica. Silver, with the lowest Tammann temperature among noble metals, is highly prone to sintering which is adequately controlled by alloying with Pd as well as encapsulation in silica. Its enhanced activity in paranitrophenol reduction in comparison with pure metals indicates the advantageous effect of alloying. (C) 2014 Elsevier B.V. All rights reserved.

}, keywords = {Ag-Pd alloy, Encapsulation, Sinter resistant, Sintering, Ultra small nanoclusters}, issn = {0920-5861}, doi = {10.1016/j.cattod.2014.11.006}, author = {Mondal, Sourik and Samanta, Anupam and Dhar, Basab B. and Devi, R. Nandini} } @article {46008, title = {Magnetic properties of sintered CoFe2O4-BaTiO3 particulate magnetoelectric composites}, journal = {Ceramics International}, volume = {45}, year = {2019}, month = {JUN}, pages = {12307-12311}, type = {Article}, abstract = {

The magnetic properties of sintered particulate magnetoelectric CoFe2O4 - BaTiO3 composites have been studied. The particulate composites are sintered in the temperature range 1000-1300 degrees C, for a short duration of 10 min. The magnetic transition temperature (T-c) of CoFe2O4 is found to decrease with increasing the sintering temperature and sintering time, as well as on increasing the BaTiO3 content in the composites. Similarly, a reduced saturation magnetization at room temperature, compared to that expected for the CoFe2O4 content, is also observed. Powder X-ray diffraction studies showed the presence of the impurity phase related to the hexagonal ferrite BaFe12O19 in all the composites. Ba2Fe2Ti4O13 is observed as a second impurity phase in the BaTiO3 - rich composites. The present studies suggest that the composition of the piezomagnetic (CoFe2O4) phase in the CoFe2O4 - BaTiO3 magnetoelectric composite is affected during the sintering process.

}, keywords = {composites, magnetic properties, Sintering}, issn = {0272-8842}, doi = {10.1016/j.ceramint.2019.03.145}, author = {Mohan, S. and Joy, P. A.} }