@article { ISI:000227447800012, title = {Coprecipitation technique to prepare BaNb2O6}, journal = {Materials Science and Engineering B-Solid State Materials for Advanced Technology}, volume = {117}, number = {2}, year = {2005}, month = {MAR}, pages = {169-171}, publisher = {ELSEVIER SCIENCE SA}, type = {Article}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

A mixture of ammonium oxalate and ammonium hydroxide was used to coprecipitate barium and niobium ions as barium oxalate and niobium hydroxide under basic conditions. This precursor on calcination at 750degreesC yielded BaNb2O6 ceramics. This is a much lower temperature as compared to that prepared by traditional solid-state method (1000degreesC), as reported for the formation of BaNb2O6. Transmission electron microscope (TEM) investigations revealed that the average particle size is 100 nm for the calcined powders. The room temperature dielectric constant at 1 kHz is found to be 1100. The ferroelectric hysteresis loop parameters of these samples were also studied. (C) 2004 Elsevier B.V. All rights reserved.

}, keywords = {Ammonia, Ceramics, Electron microscopy, niobium oxide, Oxides}, issn = {0921-5107}, doi = {10.1016/j.mseb.2004.11.009}, author = {Natarajan, N and Samuel, V and Pasricha, R and Ravi, V} } @article { ISI:000230160700011, title = {Coprecipitation technique to prepare SrNb2O6}, journal = {Materials Characterization}, volume = {55}, number = {1}, year = {2005}, month = {JUL}, pages = {92-95}, publisher = {ELSEVIER SCIENCE INC}, type = {Article}, address = {360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA}, abstract = {

A mixture of ammonium oxalate and ammonium hydroxide was used to co-precipitate strontium and niobium ions as strontium oxalate and niobium hydroxide under basic conditions. This precursor yielded SrNb2O6 ceramics on calcining at 650 degrees C. This is a much lower temperature compared to preparation of SrNb2O6 by the traditional solid state method (900 degrees C). Transmission electron microscopy (TEM) revealed that the average particle size is 100 nm for the calcined powders. The room temperature dielectric constant at 1 kHz is found to be 550. The ferroelectric hysteresis loop parameters of these samples were also studied. (c) 2005 Elsevier Inc. All rights reserved.

}, keywords = {Ceramics, Electron microscopy, ferroelectric, Oxides, X-ray methods}, issn = {1044-5803}, doi = {10.1016/j.matchar.2005.04.002}, author = {Ravi, V} } @article { ISI:000232864800029, title = {Low temperature synthesis of MgTa2O6 powders}, journal = {Materials Letters}, volume = {59}, number = {29-30}, year = {2005}, month = {DEC}, pages = {3926-3928}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A combination of digestion and further low temperature calcination to crystallize the product is employed to prepare MgTa2O6 (MT) ceramics. Freshly prepared niobium hydroxide gel is mixed with magnesium hydroxide thoroughly and allowed to react at 100 degrees C under refluxing and stirring conditions for 6-12 h. The X-ray amorphous product so formed is heated at 550 degrees C to form crystalline MgTa2O6. This is the lowest temperature so far reported for the formation of MgTa2O6. For comparison, MT powders were also prepared by the traditional solid state method. Transmission electron microscope (TEM) investigations revealed that the average particle size is 40 nm for the low temperature calcined powders. (C) 2005 Elsevier B.V. All rights reserved.

}, keywords = {Ceramics, Electron microscopy, magnesium tantalate, Oxides, X-ray diffraction}, issn = {0167-577X}, doi = {10.1016/j.matlet.2005.07.035}, author = {Navale, SC and Samuel, V and Ravi, V} } @article { ISI:000228253200008, title = {Preparation of nanocrystalline ferroelectric BaNb(2)O6 by citrate gel method}, journal = {Bulletin of Materials Science}, volume = {28}, number = {2}, year = {2005}, month = {APR}, pages = {121-123}, publisher = {INDIAN ACADEMY SCIENCES}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, abstract = {

A gel was formed when a aqueous solution of BaCl2, NbF5 and citric acid in stoichiometric ratio is heated on a water bath. This gel on decomposition at 600 degrees C yielded the nano crystallites of BaNb2O6, as confirmed by X-ray diffraction study (XRD). This is a much lower temperature as compared to that prepared by traditional solid state method (1000 degrees C) as reported for the formation of BaNb2O6. Transmission electron microscopic. (TEM) investigations revealed that the average particle size is 50 nm for the calcined powders. The room temperature dielectric constant at 1 kHz is found to be 1000. The ferroelectric hysteresis loop parameters of these samples were also studied.

}, keywords = {Ceramics, Chemical synthesis, electronic material, ferroelectricity, Oxides}, issn = {0250-4707}, doi = {10.1007/BF02704230}, author = {Gaikwad, S. P. and Samuel, V and Pasricha, R and Ravi, V} } @article { ISI:000231592300006, title = {Synthesis of Sr0.5Ba0.5Nb2O6 by citrate gel method}, journal = {Materials Chemistry and Physics}, volume = {94}, number = {1}, year = {2005}, month = {NOV}, pages = {34-36}, publisher = {ELSEVIER SCIENCE SA}, type = {Article}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

A gel was formed when an aqueous solution of BaCl2, SrCl2, NbF5 and citric acid in stoichiometric ratio is heated on a water bath. This gel on decomposition at 700 degrees C yielded the nanocrystallites of ternary oxide, Sr0.5Ba0.5Nb2O6 (SBN) as confirmed by X-ray diffraction study (XRD). Particle size and morphology was studied by transmission electron spectroscopy (TEM). The room temperature dielectric constant at I kHz is 1000. The ferroelectric hysteresis loop parameters of these samples were also studied by a home built Sawyer-Tower circuit. (c) 2005 Elsevier B.V. All rights reserved.

}, keywords = {Ceramics, Electron microscopy, ferroelectricity, Oxides}, issn = {0254-0584}, doi = {10.1016/j.matchemphys.2005.04.003}, author = {Pasricha, R and Ravi, V} } @article { ISI:000232196200008, title = {TiO2 ceramic varistor modified with tantalum and barium}, journal = {Materials Science and Engineering B-Solid State Materials for Advanced Technology}, volume = {123}, number = {1}, year = {2005}, month = {NOV}, pages = {50-52}, publisher = {ELSEVIER SCIENCE SA}, type = {Article}, address = {PO BOX 564, 1001 LAUSANNE, SWITZERLAND}, abstract = {

The non-linear current (I)-voltage (V) characteristics of titanium dioxide doped with small quantities of tantalum and barium (99.9 TiO2 + 0.1 Ta and 99.4 TiO2 + 0.1 Ta + 0.5 Ba, all are in at.\%) were investigated. These samples have the non-linear coefficient (alpha) values of (20-30) with high breakdown voltages (E-B similar to 400-700 V mm(-1)). The pentavalent tantalum acts as donor and increases the electronic conductivity. The higher electrical conductivity and decrease in the breakdown field strength with barium addition is attributed to higher density. The acceptor like surface states formed by barium ions segregate to grain boundaries due size misfit to thereby modifying the electrical barrier characteristics of grain boundaries. (c) 2005 Elsevier B.V. All rights reserved.

}, keywords = {Ceramics, Oxides, TiO2, varistor, X-ray diffraction}, issn = {0921-5107}, doi = {10.1016/j.mseb.2005.06.015}, author = {Gaikwad, A. B. and Navale, SC and Ravi, V} } @article { ISI:000237439300005, title = {Coprecipitation technique to prepare NaNbO3 and NaTaO3}, journal = {Bulletin of Materials Science}, volume = {29}, number = {2}, year = {2006}, month = {APR}, pages = {123-125}, publisher = {INDIAN ACADEMY SCIENCES}, type = {Article}, address = {C V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIA}, abstract = {

A simple coprecipitation technique has been used successfully for the preparation of pure, ultrafine, single phases of NaNbO3 (NN) and NaTaO3 (NT). An alcoholic solution of ammonium carbonate and ammonium hydroxide was used to precipitate Na+ and Nb5+ (or Ta5+) cations under basic conditions as carbonate and hydroxide, respectively. On heating at 700 degrees C, these precursors produce respective products. For comparison, both NN and NT powders were also prepared by the traditional solid state method. The phase purity and lattice parameters were studied by powder X-ray diffraction (XRD). The particle size and morphology were studied by scanning electron microscopy (SEM).

}, keywords = {Ceramics, Chemical synthesis, Electron microscopy, electronic materials, Oxides, X-ray methods}, issn = {0250-4707}, doi = {10.1007/BF02704604}, author = {Samuel, V and Gaikwad, A. B. and Ravi, V} }