Research Papers/Topics in Chemistry
Investigations of Nano-crystalline Sr0.5Ba0.5Nb2O6 and Bulk Ceramics Synthesized by a Polymerization Method using PEG400
Abstract.J. Eur. Ceram. Soc. 39 (2019) 1156–1163. (DOI: 10.1016/j.jeurceramsoc.2018.11.043). Nano-crystalline Sr0.5Ba0.5Nb2O6 was synthesized by a one-pot method using PEG400 and citric acid. Calcination of the (Sr,Ba,Nb)-gel at 600 °C leads to Sr0.5Ba0.5Nb2O6 with a crystallite size of 24(2) nm and a specific surface area of 38.5(10) m2 g-1. Sintering upto 1325 °C leads to ceramics with globular or irregular-shaped grains and average grain sizes between 1.3 and 2.4 μm, whereas higher te...
Preparation and Characterization of Nano-sized Magnesium Ferrite Powders by a Starch-gel Process and Corresponding Ceramics
Abstract:J. Mater. Sci. 48 (2013) 6509–6518. (DOI: 10.1007/s10853-013-7447-x).The synthesis and characterization of nano-sized MgFe2O4 by a starch-gel method is described herein. A phase-pure nano-sized MgFe2O4 powder (1a) was obtained after calcining a (MgFe)-starch gel at 550 °C. The powder has a specific surface area of 60.6 m2/g and a crystallite size of 9 nm. TEM investigations reveal particles in the range of 7 to 15 nm. The activation energy of the crystallite gr...
BaGeO3 as Sintering Additive for BaTiO3-MgFe2O4 Composite Ceramics.
Abstract:RSC Adv. 5 (2015) 71491 (Open Access, DOI: 10.1039/c5ra12312g).BaTiO3-MgFe2O4 composites (30 wt.% MgFe2O4) with a small addition of BaGeO3 as a sintering additive were synthesized by a one-pot Pechini-like sol-gel process. Nano-crystalline composite powders with a crystallite size of about 10 nm were obtained after reaction at 700 °C for 1 h. Magnetic investigations suggest that the nano-powder is in its superparamagnetic state at room temperature. The addition of BaGeO3 leads to an...
Thermoanalytical, Optical, and Magnetic Investigations on Nanocrystalline Li0.5Fe2.5O4 and Resulting Ceramics Prepared by a Starch-based Soft-chemistry Synthesis.
Abstract. J. Solid State Chem. 287 (2020) 121380. (DOI: 10.1016/j.jssc.2020.121380).Nanocrystalline Li0.5Fe2.5O4 was prepared by a starch-based soft-chemistry synthesis. Calcining of the (LiFe)-gel between 350 and 1000 °C results in Li0.5Fe2.5O4 powders with crystallite sizes from 13 to 141 nm and specific surface areas between 35 and 7.1 m2 g-1. XRD investigations reveal the formation of ordered Li0.5Fe2.5O4. Sintering between 1050 and 1250 °C leads to ceramics with relative densities o...
Magnetic and Optical Investigations on LaFeO3 Powders with Different Particle Sizes and Corresponding Ceramics
Abstract.Solid State Ionics 249–250 (2013) 1–5. (DOI: 10.1016/j.ssi.2013.07.001). The optical and magnetic properties of nano-LaFeO3 powders prepared by a starch assisted soft-chemistry synthesis and corresponding ceramics have been investigated. Magnetic measurements on LaFeO3 powders with crystallite sizes of 37−166 nm showpronounced magnetization hysteresis loops. Measurements at 300 K reveal that the coercivity (Hc) of 19−32 kOe depends on the crystallite size, whereas the low ...
Synthesis and Characterization of Nano-LaFeO3 Powders by a Softchemistry Method and Corresponding Ceramics
Abstract. Solid State Ionics 231 (2013) 43–48. (DOI: 10.1016/j.ssi.2012.10.017).The preparation of a nano-sized LaFeO3 powder by a soft-chemistry method using starch as complexing agent is described herein. Phase evolution and development of the specific surface area during the decomposition process of (LaFe)-gels were monitored up to1000 °C. A phase-pure nano-sized LaFeO3 powder with a high specific surface area of 25.7 m2/g and a crystallite size of 37 nm was obtained after calcining ...
Crystallite Growth, Phase Transition, Magnetic Properties, and Sintering Behaviour of Nano-CuFe2O4 Powders Prepared by a Combustion-like Process
Abstract.J. Solid State Chem. 213 (2014) 57–64. (DOI: 10.1016/j.jssc.2014.02.010). The synthesis of nano-crystalline CuFe2O4 powders by a combustion-like process is described herein. Phase formation and evolution of the crystallite size during the decomposition process of a (CuFe2)-precursor gel were monitored up to 1000 °C. Phase-purenano-sized CuFe2O4 powders were obtained after reaction at 750 °C for 2 h resulting in a crystallite size of 36 nm, which increases to 96 nm after calcin...
Synthesis, Phase Evolution and Properties of Phase-pure Nanocrystalline BiFeO3 Prepared by a Starch-based Combustion Method
Abstract.J. Alloys Compd. 590 (2014) 324–330. (DOI: 10.1016/j.jallcom.2013.12.120). The preparation of phase-pure nano-sized BiFeO3 by a combustion-like method using starch as complexing agent is described herein. Phase evolution and development of the crystallite size during the synthesis were monitored depending on the heat treatment and the composition of the (BiFe)-gels. Phase-pure BiFeO3 was obtained at a low heating rate and calcination temperatures between 500 ...
Investigations on Bi25FeO40 Powders Synthesized by Hydrothermal and Combustion-like Processes
Abstract. J. Solid State Chem. 217 (2014) 50–56. (DOI: 10.1016/j.jssc.2014.05.006).The syntheses of phase−pure and stoichiometric iron sillenite (Bi25FeO40) powders by a hydrothermal (at ambient pressure) and a combustion−like process are described. Phase−pure samples were obtained in the hydrothermal reaction at 100 °C (1), whereas thecombustion−like process leads to pure Bi25FeO40 after calcination at 750 °C for 2 h (2a). The activation energy of the crystallite growth proces...
Magnetic, Optical, Dielectric, and Sintering Properties of Nano-crystalline BaFe0.5Nb0.5O3 Synthesized by a Polymerization Method.
Abstract. J. Mater. Sci. 53 (2018) 1024–1034. (DOI: 10.1007/s10853-017-1609-1).A one-pot polymerization method using citric acid and glucose for the synthesis of nano-crystalline BaFe0.5Nb0.5O3 is described. Phase evolution and the development of the crystallite size during decomposition of the (Ba,Fe,Nb)-gel were examined up to 1100 °C. Calcination at 850 °C of the gel leads to a phase-pure nano-crystalline BaFe0.5Nb0.5O3 powder with a crystallite size of 28 nm. T...
Investigations of BaFe0.5Nb0.5O3 Nano Powders Prepared by a Low Temperature Aqueous Synthesis and Resulting Ceramics
Abstract. J. Eur. Ceram. Soc. 37 (2017) 1509–1516. (DOI: 10.1016/j.jeurceramsoc.2016.12.014).A facile method to prepare nanoscaled BaFe0.5Nb0.5O3 via synthesis in boiling NaOH solution is described herein. The nano-crystalline powder has a high specific surface area of 55 m2 g−1 and a crystallite size of 15 nm. The as-prepared powder does not show anysignificant crystallite growth up to 700 °C. The activation energy of the crystallite growth process was calculated as 590 kJ mol−1. ...
Fine-grained BaTiO3-MgFe2O4 composites prepared by a Pechini-like process
Abstract. J. Alloys Compd. 368 (2015) 141–147. (DOI: 10.1016/j.jallcom.2015.03.082). The synthesis of BaTiO3-MgFe2O4 composite powders by a Pechini-like one-pot process and resulting ceramic bodies is described herein. Phase formation during the decomposition of homogenous (Ba,Ti,Fe,Mg)-gels was monitored up to 1200 °C. Composite powders consisting of BaTiO3 and MgFe2O4 were obtained after decomposition at 700 °C for 1 h resulting in crystallite sizes of about 10 nm. The shrinkage a...
Preparation and Sintering Behaviour of a Fine Grain BaTiO3 Powder Containing 10 mol% BaGeO3
Abstract. J. Mater. Sci. 43 (2008) 832-838. (DOI: 10.1007/s10853-007-2195-4).The formation of solid solutions of the type [Ba(HOC2H4OH)4][Ti1-xGex(OC2H4O)3] as Ba(Ti1-x/Gex)O3 precursors and the phase evolution during thermal decomposition of [Ba(HOC2H4OH)4][Ti0.9Ge0.1(OC2H4O)3] (1) are described herein. The 1,2- ethanediolato complex 1 decomposes above 589 °C to a mixture of BaTiO3 and BaGeO3. A heating rate controlled calcination procedure up to 730 °C leads to a nm-size...
Shrinkage Mechanism and Phase Evolution of Fine-grain BaTiO3 Powder Compacts Containing 10 mol% BaGeO3 Prepared via a Precursor Route
Abstract. Mater. Chem. Phys. 112 (2008) 531-535. (DOI: 10.1016/j.matchemphys.2008.06.005).The shrinkage mechanism of BaTiO3 powder compacts containing 10 mol% BaGeO3, synthesized by a precursor route and a conventional mixed-oxide method, are described herein. The calcination of a barium titanium germanium 1,2-ethanediolato complex precursor - [Ba(HOC2H4OH)4][Ti0.9Ge0.1(OC2H4O)3] (1) - at 730 °C leads to a nm-sized Ba(Ti0.9/Ge0.1)O3 powder (1a) (SBET = 16.9 m2/g) consi...
Phase Transition and Dielectric Properties of BaTiO3 Ceramics Containing 10 mol% BaGeO3
Abstract. Mater. Chem. Phys. 119 (2010) 118-122. (DOI: 10.1016/j.matchemphys.2009.08.026).Dielectric properties and the cubic tetragonal phase transition temperature of dense BaTiO3 ceramics containing 10 mol% BaGeO3, sintered between 840 and 1350 °C, have been investigated. The ceramic bodies were prepared from a nano-sized BaTi0.9/Ge0.1O3 powder consisting of both BaTiO3 and BaGeO3 phases. The addition of BaGeO3 leads to a reduction and broadening of the permittivi...