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. Den...
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 and sin...
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-sized Ba(Ti0.9/Ge...
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) consisting of BaTiO3 an...
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 permittivity maximum, and to a...
Abstract. J. Eur. Ceram. Soc. 29 (2009) 2317-2324. (DOI: 10.1016/j.jeurceramsoc.2009.01.026). Preparation of a very fine BaSnO3 powder by calcination of a barium tin 1,2-ethanediolato complex precursor and its sintering behaviour are described herein. A rate controlled calcination process to 820 °C leads to a nm-sized BaSnO3 powder with a specific surface area of S = 15.1 m2/g (dav. = 55 nm). The powder has a slightly larger cell parameter of a = 412.22(7) pm compared to the single cryst...
Abstract. Thermochim. Acta 441 (2006) 176-183. (DOI: 10.1016/j.tca.2005.12.010). The thermal behaviour of [Ba(C2H6O2)4][Sn(C2H4O2)3] used as a BaSnO3 precursor, and its phase evolution during thermal decomposition are described. The initially formed transient barium-tin-oxycarbonate phase disintegrates into BaCO3 and SnO2, reacting subsequently to BaSnO3. The existence of the intermediate oxycarbonate phase is evidenced by FT-IR, XRD, and EELS (ELNES) investigations.
Abstract. J. Eur. Ceram. Soc. 30 (2010) 1419-1425. (DOI: 10.1016/j.jeurceramsoc.2009.12.015). DTA, XRD and sintering investigations of the system BaSnO3−BaGeO3, prepared by a mixed-oxide method, are described herein. The melting temperature of this system is about 1270 ± 5 °C. We find a partial solubility of BaGeO3 into BaSnO3 of the order of 6−7 mol%. Up to 50 mol% BaGeO3, the calcined powders (1150 °C) as well as the once-sintered samples consist of BaSnO3 and orthorhombic BaGeO3 at ...
Abstract. J. Mater. Sci. 45 (2010) 3784–3790. (DOI: 10.1007/s10853-010-4432-5). The formation of solid solutions of the type [Ba(HOC2H4OH)4][Sn1−xGex(OC2H4O)3] as BaSn1-x/GexO3 precursor and the phase evolution during its thermal decomposition are described in this paper. The 1,2-ethanediolato complexes can be decomposed to nano-sized BaSn1−x/GexO3 preceramic powders. Samples with x = 0.05 consist of only a Ba(Sn,Ge)O3 phase, whereas powders with x = 0.15 and 0.25 show diffraction patte...
Abstract. Z. Anorg. Allg. Chem. 629 (2003) 371-373. (DOI: 10.1002/zaac.200390061). Colourless single crystals of BaC4O4 have been obtained from aqueous solution at 80 °C. BaC4O4 is stable in air up to 490 °C. BaCO3 is formed by further increase of temperature. BaC4O4 crystallizes in the tetragonal space group I4/mcm (nr. 140) with a=635.95(5),c=1240.77(13) pm, Z=4. Ba2+ is coordinated by eight oxygen atoms of the squarate dianions; Ba—O 276.1(1) pm. The coordination polyhedron is a distor...
Abstract. Z. Anorg. Allg. Chem. 641 (2015) 1150–1155. (DOI: 10.1002/zaac.201500050). Monoclinic single crystals of Ba2(H2O)[μ10-C6H2(COO)4] (1) and Pb2(H2O)[μ10- C6H2(COO)4] (2) were obtained using the silica gel method [space group C2/c (no. 15), Z = 4; 1: a = 780.89(4), b = 1756.19(8), c = 914.80(5) pm, β = 114.512(5)°; 2: a = 756.70(10), b =1772.8(2), c = 890.2(2) pm, β = 113.590(10)°]. There are two crystallographically independent M2+ ions (M = Ba, Pb). M(1) is surrounded by eigh...
Abstract 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. The shrinkage of compacted powders starts at 900 °C. Dense ceramic bodies (relative densit...
Abstract: Thermochim. Acta 457 (2007) 55-63. (DOI: 10.1016/j.tca.2007.02.021). The thermal behaviour of [Ba(HOC2H4OH)2Ge(OC2H4O)3] (2) as a BaGeO3 precursor, and its phase evolution during thermal decomposition in different atmospheres are described herein. The precursor complex decomposes in air to a finely divided mixture of BaCO3 and GeO2, which subsequently reacts above 650 °C to orthorhombic BaGeO3, transforming above 800 °C to hexagonal BaGeO3. The shrinkage behaviour of BaGeO3 co...
Abstract. Solid State Ionics 203 (2011) 52–56. (DOI: 10.1016/j.ssi.2011.09.010). The preparation of nano-sized BaCeO3 powder using starch as a polymerization agent is described herein. Phase evolution during the decomposition process of a (BaCe)-gel was monitored by XRD. A phase-pure nano-sized BaCeO3 powder was obtained after calcining of the (BaCe)-gel at 920 °C. The resulting powder has a specific surface area of 15.4m2/g. TEM investigations reveal particles mainly in the size range ...
Abstract. J. Mater. Sci. 45 (2010) 6521–6527. (DOI: 10.1007/s10853-010-4741-8). The formation of BaCeO3 by a co-precipitation method is described herein. The coprecipitation route leads to an orange (BaCe)-precursor powder (1). To improve the sintering behaviour, a small amount of Ge4+ was incorporated, leading to a (BaCe0.95/Ge0.05)-precursor (2). Both precursor powders results in fine-grained preceramic powders (1A, 2A) after calcination. The shrinkage and sintering behaviour of resulti...