Search results for: T.R.N. Kutty

Items from 1 to 20 out of 56 results

article

Gel- to -crystallite conversion technique for the syntheses of M-β/β″-alumina (M=Li, Na, K, Rb, Ca or Eu)

V. Jayaraman, G. Periaswami, T.R.N. Kutty

Materials Research Bulletin > 2008 > 43 > 10 > 2527-2537

Various alkali and alkaline earths hydroxides are reacted with hydrated alumina gel Al ₂ O ₃ ·nH ₂ O (80<n<120) in hydrophilic organic solvents to yield precursor(s) with metal cation entrapped in the matrix, with the general formula M _y AlO _y (OH) _3−y (where M=Li, Na, K, Rb, Ca and Eu). Depending on the cation, the precursor crystallizes as metal-inserted...

article

X-ray photoelectron spectroscopic investigations on cubic BaTiO3, BaTi0.9Fe0.1O3 and Ba0.9Nd0.1TiO3 systems

Hrudananda Jena, V.K. Mittal, Santanu Bera, S.V. Narasimhan, more

Applied Surface Science > 2008 > 254 > 21 > 7074-7079

X-ray photoelectron spectroscopic (XPS) studies were carried out on wet-chemically synthesized cubic BaTiO ₃ , Ba _0.9 Nd _0.1 TiO ₃ and BaTi _0.9 Fe _0.1 O _3−δ powders. The compounds were prepared by hydrothermal and gel to crystallite conversion technique; and phases formed readily at 420K. The phase purity of the powders was confirmed from X-ray...

article

Microwave dielectric properties of Mg4Al2Ti9O25 ceramics

S. Jayanthi, T.R.N. Kutty

Materials Letters > 2008 > 62 > 3 > 556-560

Phase-singular Mg ₄ Al ₂ Ti ₉ O ₂₅ ceramics with the pseudobrookite structure suitable for microwave devices such as antenna substrate have been prepared by gel-carbonate method with the dielectric permittivity of 24.7 (at 2–8 GHz), Q-values>30,000 and temperature coefficients in permittivity (TCK) of less than +17 ppm K ⁻¹ . The dielectric characteristics...

article

Preparation of BaTi4O9 and Ba2Ti9O20 ceramics by the wet chemical gel-carbonate method and their dielectric properties

Sanjiv Kumar, V.S. Raju, T.R.N. Kutty

Materials Science & Engineering B > 2007 > 142 > 2-3 > 78-85

Preparation of BaTi ₄ O ₉ and Ba ₂ Ti ₉ O ₂₀ ceramics by the wet chemical gel-carbonate method, and their microstructural and dielectric properties are presented. Monophasic Ba ₂ Ti ₉ O ₂₀ of triclinic symmetry having high dielectric constant (ɛ _r ∼52 at 1MHz), low temperature coefficient of dielectric constant (τ _ɛ ∼6ppm/°C)...

article

Calcium zinc manganites, Ca4Mn7Zn3O21−δ (0.5<δ<2.5) with beta-alumina or magnetoplumbite-type structure and their nonlinear electrical transport and magnetic properties

K. Vijayanandhini, T.R.N. Kutty

Materials Letters > 2007 > 61 > 17 > 3652-3657

Phase-pure calcium zinc manganite, Ca ₄ Mn ₇ Zn ₃ O ₂₁ ₋ _δ has been synthesized by the solid-state reaction between CaMnO ₃ , ZnO and Mn ₃ O ₄ at ∼1300 °C. Conversion of Ca ₄ Mn ₇ Zn ₃ O ₂₁ ₋ _δ to Ca ₄ Mn ₇ Zn ₃ O ₁₉ _± _δ occurs at 1330–1350 °C which is influenced...

article

Effects of Zn substitution on the magnetic and transport properties of La0.6Sr0.4Mn1−yZnyO3−δ (0≤y≤0.3)

K. Vijayanandhini, T.R.N. Kutty

Solid State Communications > 2007 > 141 > 5 > 252-257

Phase-singular solid solutions of La _0.6 Sr _0.4 Mn _1−y Zn _y O _3−δ (0≤y≤0.3) [LSMZO] perovskite of rhombohedral symmetry (space group: R3¯c) with y up to 30 at.% could be synthesized notwithstanding the differences in ionic radii of Mn _{V I} ³⁺ (i.r.=0.645 Å) and Zn _{V I} ²⁺ (i.r.=0.74 Å). The LSMZO≤02 compositions are ferromagnetic metallic...

article

Self-assembly of doped semiconductor nanocrystals leading to the formation of highly luminescent nanorods

K. Manzoor, V. Aditya, S.R. Vadera, N. Kumar, more

Applied Surface Science > 2006 > 252 > 11 > 3968-3971

Meso-scale self-assembly of doped semiconductor nanocrystals leading to the formation of monocrystalline nanorods showing enhanced photo- and electro-luminescence properties are reported. Polycrystalline ZnS: Cu ⁺ –Al ³⁺ nanoparticles of zinc-blended (cubic) structure with an average size of ∼4nm were aggregated in aqueous solution and grown into nanorods of length ∼400nm and aspect...

article

Dielectric properties of barium magnesiotitanate ceramics, BaMg6Ti6O19

S. Jayanthi, T.R.N. Kutty

Materials Letters > 2006 > 60 > 6 > 796-800

Phase-pure samples of barium magnesiotitanate, BaMg ₆ Ti ₆ O ₁₉ (BMT) are prepared by the wet chemical ‘gel–carbonate’ method wherein the formation of BMT is complete below 950 °C as a result of the reaction between nanoparticles of BaCO ₃ , MgO and TiO ₂ . BMT powders are sintered at 1350–1450 °C to dense ceramics. Extensive melting is noticed when the bulk...

article

Electrochemical co-deposition of ternary Sn–Bi–Cu films for solder bumping applications

Shany Joseph, Girish J. Phatak, K. Gurunathan, Tanay Seth, more

Journal of Applied Electrochemistry > 2006 > 36 > 8 > 907-912

This paper reports the co-deposition of Sn–Bi–Cu films using stannic salt bath which has good stability for up to a week. The effect of current density and bath stirring on the film composition and microstructure has been studied. The deposited films are rich in the more noble metal Bi at current densities up to 5 mA cm⁻² but stabilize to about 49 wt. % Bi, 47 wt. % Sn and 4 wt. % Cu at 10 mA cm⁻²...

article

Studies on surface composition and chemical states of calcium manganites

Sanjiv Kumar, V.S. Raju, Santanu Bera, K. Vijaynandhini, more

Nuclear Inst. and Methods in Physics Research, B > 2005 > 237 > 3-4 > 623-630

This paper describes investigations on atomic composition and chemical states of sintered calcium manganites discs in surface and near surface regions. The atomic composition was determined by 3.05MeV ¹⁶ O(α,α) ¹⁶ O resonance elastic scattering while the chemical states by, X-ray photoelectron spectroscopy (XPS). The specimens examined included undoped and donor (Y ³⁺ , Bi...

article

Enhanced electroluminescence properties of doped ZnS nanorods formed by the self-assembly of colloidal nanocrystals

K. Manzoor, V. Aditya, S.R. Vadera, N. Kumar, more

Solid State Communications > 2005 > 135 > 1-2 > 16-20

Aggregation based meso-scale self-assembly of doped semiconductor nanocrystals leading to the formation of monocrystalline nanorods showing enhanced photo- and electro-luminescence properties is reported. ∼4nm sized, polycrystalline ZnS nanoparticles of zinc-blende (cubic) structure, doped with Cu ⁺ –Al ³⁺ have been aggregated in the aqueous solution and grown into nanorods of length...

article

Spontaneous organisation of ZnS nanoparticles into monocrystalline nanorods with highly enhanced dopant-related emission

K. Manzoor, V. Aditya, S.R. Vadera, N. Kumar, more

Journal of Physics and Chemistry of Solids > 2005 > 66 > 7 > 1164-1170

A natural self-assembly process of semiconductor nanoparticles leading to the formation of doped, monocrystalline nanorods with highly enhanced dopant-related luminescence properties is reported. ∼4nm sized, polycrystalline ZnS nanoparticles of zinc-blende (cubic) structure, doped with Cu ⁺ -Al ³⁺ or Mn ²⁺ have been aggregated in the aqueous solution and grown into nanorods...

article

Photoluminescence due to efficient energy transfer from Ce3+ to Tb3+ and Mn2+ in Sr3Al10SiO20

Abanti Nag, T.R.N. Kutty

Materials Chemistry and Physics > 2005 > 91 > 2-3 > 524-531

Sr ₃ Al ₁₀ SiO ₂₀ , doped with Ce ³⁺ , Tb ³⁺ , Eu ²⁺ , (Ce ³⁺ +Tb ³⁺ ), (Ce ³⁺ +Mn ²⁺ ), (Eu ²⁺ +Tb ³⁺ ) and (Eu ²⁺ +Mn ²⁺ ) are prepared by wet-chemical route and energy transfer from Ce ³⁺ to Tb ³⁺ or Mn ²⁺ are investigated. The spectrum of Sr ₃ Al ₁₀...

article

Effect of interface states associated with transitional nanophase precipitates in the enhancement of red emission from SrAl12O19:Pr3+ by Ti4+ incorporation

Abanti Nag, T.R.N. Kutty

Journal of Physics and Chemistry of Solids > 2005 > 66 > 1 > 191-199

SrAl ₁₂ O ₁₉ :Pr ³⁺ , Ti ⁴⁺ phosphor suitable for field emission displays is prepared by the wet chemical gel-carbonate method and the mechanism of enhancement in red photoluminescence (PL) intensity with Ti ⁴⁺ therein has been investigated. The PL spectra of Pr ³⁺ show both ¹ D ₂ – ³ H ₄ and ³ P ₀ – ...

article

Ionic transport and structural investigations on MSn(OH)6 (M = Ba, Ca, Mg, Co, Zn, Fe, Mn) hydroxide perovskites synthesized by wet sonochemical methods

Hrudananda Jena, K.V. Govindan Kutty, T.R.N. Kutty

Materials Chemistry and Physics > 2004 > 88 > 1 > 167-179

Hydroxide perovskites of MSn(OH) ₆ (M = Ba, Ca, Mg, Co, Zn, Fe or Mn) were synthesized by co-precipitation and sonochemical reaction routes. Some of the compounds were also prepared by the hydrothermal method. These were characterized by XRD, TGA/DTA, TEM and IR studies. The hydroxide perovskites are stable up to ∼523K and all the compounds stabilize in cubic crystal system (SG = Pn3m) at...

article

Novel wet chemical synthesis and ionic transport properties of LaGaO3 and selected doped compositions at elevated temperatures

Hrudananda Jena, K.V. Govindan Kutty, T.R.N. Kutty

Materials Science & Engineering B > 2004 > 113 > 1 > 30-41

LaGaO ₃ , La _0.9 Ga _0.8 Mn _0.1 O ₃₋ _δ and La _0.9 Sr _0.05 Ga _0.8 Li _0.01 O ₃₋ _δ synthesized by the decomposition of metal nitrate–tartarate complex were found to yield the cubic phase on heat treatment at 1023–1273K; above which they transformed to distorted cubic phase (orthorhombic). LaGaO ₃ was also synthesized...

article

Structural and magnetic characteristics of cobalt ferrite-coated nano-fibrous γ-Fe ₂ O ₃

C. Sudakar, T.R.N. Kutty

Journal of Magnetism and Magnetic Materials > 2004 > 279 > 2-3 > 363-374

The presence of mesopores in γ-Fe ₂ O ₃ is a limiting factor for its optimal magnetic properties. Therefore, high coercive γ-Fe ₂ O ₃ nano-fibrous particles are obtained by coating cobalt ferrite on the surface. An aqueous solution of cobalt nitrate+ammonium ferrous sulphate (in the ratio 1:2) precipitated at pH>12.5 in the presence of uniformly dispersed γ-Fe ...

article

Extended phase homogeneity and electrical properties of barium calcium titanate prepared by the wet chemical methods

S. Jayanthi, T.R.N. Kutty

Materials Science & Engineering B > 2004 > 110 > 2 > 202-212

Ca-substituted BaTiO ₃ with extended homogeneity range upto ~50mol% CaTiO ₃ have been prepared by three different chemical routes namely carbonate-oxalate (COBCT), gel-carbonate (GCBCT), and gel-to-crystallite conversion (GHBCT) followed by heat treatment above 1150 ^o C. X-ray powder diffraction (XRD) data show continuous decrease in the tetragonal unit cell parameters as well...

article

Eu ³ ⁺ doped yttrium oxysulfide nanocrystals - crystallite size and luminescence transition(s)

J. Dhanaraj, M. Geethalakshmi, R. Jagannathan, T.R.N. Kutty

Chemical Physics Letters > 2004 > 387 > 1-3 > 23-28

Nanocrystals of yttrium oxysulfide doped with trivalent europium has been synthesized using a two step sol-gel polymer thermolysis method employing urea formaldehyde resin in the presence of ethylene diamine tetra acetic acid as chelating agent. In this synthesis, marginal tunability in crystallite size (φ = 7-15 nm) was achieved by varying the concentration of reactants and organic precursors. In...

article

The mechanism of long phosphorescence of SrAl ₂ _- _x B _x O ₄ (0<x<0.2) and Sr ₄ Al ₁ ₄ _- _x B _x O ₂ ₅ (0.1<x<0.4) co-doped with Eu ² ⁺ and Dy ³ ⁺

Abanti Nag, T.R.N. Kutty

Materials Research Bulletin > 2004 > 39 > 3 > 331-342

The role of B ₂ O ₃ in realizing the long phosphorescence of Eu(II)+Dy(III) doped strontium aluminates has been investigated. IR and solid state ² ⁷ Al MAS NMR spectra show the incorporation of boron as BO ₄ in the AlO ₄ framework of SrAl ₂ O ₄ and Sr ₄ Al ₁ ₄ O ₂ ₅ . Phosphor, made free of glassy phases by...

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Search results for: T.R.N. Kutty

Gel- to -crystallite conversion technique for the syntheses of M-β/β″-alumina (M=Li, Na, K, Rb, Ca or Eu)

X-ray photoelectron spectroscopic investigations on cubic BaTiO3, BaTi0.9Fe0.1O3 and Ba0.9Nd0.1TiO3 systems

Microwave dielectric properties of Mg4Al2Ti9O25 ceramics

Preparation of BaTi4O9 and Ba2Ti9O20 ceramics by the wet chemical gel-carbonate method and their dielectric properties

Calcium zinc manganites, Ca4Mn7Zn3O21−δ (0.5<δ<2.5) with beta-alumina or magnetoplumbite-type structure and their nonlinear electrical transport and magnetic properties

Effects of Zn substitution on the magnetic and transport properties of La0.6Sr0.4Mn1−yZnyO3−δ (0≤y≤0.3)

Self-assembly of doped semiconductor nanocrystals leading to the formation of highly luminescent nanorods

Dielectric properties of barium magnesiotitanate ceramics, BaMg6Ti6O19

Electrochemical co-deposition of ternary Sn–Bi–Cu films for solder bumping applications

Studies on surface composition and chemical states of calcium manganites

Enhanced electroluminescence properties of doped ZnS nanorods formed by the self-assembly of colloidal nanocrystals

Spontaneous organisation of ZnS nanoparticles into monocrystalline nanorods with highly enhanced dopant-related emission

Photoluminescence due to efficient energy transfer from Ce3+ to Tb3+ and Mn2+ in Sr3Al10SiO20

Effect of interface states associated with transitional nanophase precipitates in the enhancement of red emission from SrAl12O19:Pr3+ by Ti4+ incorporation

Ionic transport and structural investigations on MSn(OH)6 (M = Ba, Ca, Mg, Co, Zn, Fe, Mn) hydroxide perovskites synthesized by wet sonochemical methods

Novel wet chemical synthesis and ionic transport properties of LaGaO3 and selected doped compositions at elevated temperatures

Structural and magnetic characteristics of cobalt ferrite-coated nano-fibrous γ-Fe ₂ O ₃

Extended phase homogeneity and electrical properties of barium calcium titanate prepared by the wet chemical methods

Eu ³ ⁺ doped yttrium oxysulfide nanocrystals - crystallite size and luminescence transition(s)

The mechanism of long phosphorescence of SrAl ₂ _- _x B _x O ₄ (0<x<0.2) and Sr ₄ Al ₁ ₄ _- _x B _x O ₂ ₅ (0.1<x<0.4) co-doped with Eu ² ⁺ and Dy ³ ⁺

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