Fabrication and characterization of bismuth oxideeholmia nanofibers and nanoceramics

In this article, a novel and simple method to produce both boron doped and undoped holmia stabilized bismuth oxide nanoceramic materials has been put forward. Boron doped and undoped poly (vinyl alcohol)/bismutheholmia acetate nanofibers were produced

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  Full Terms & Conditions of access and use can be found athttp://www.tandfonline.com/action/journalInformation?journalCode=yaac20 Download by:  [Gazi University] Date:  23 January 2016, At: 07:55 Advances in Applied Ceramics Structural, Functional and Bioceramics ISSN: 1743-6753 (Print) 1743-6761 (Online) Journal homepage: http://www.tandfonline.com/loi/yaac20 Fabrication and characterisation of borondoped barium stabilised bismuth cobalt oxidenanocrystalline ceramic composite İ Uslu, E Çınar, S Koçyiğit, A Aytimur & A Akdemir To cite this article:  İ Uslu, E Çınar, S Koçyiğit, A Aytimur & A Akdemir (2013) Fabrication andcharacterisation of boron doped barium stabilised bismuth cobalt oxide nanocrystallineceramic composite, Advances in Applied Ceramics, 112:6, 336-340 To link to this article: http://dx.doi.org/10.1179/1743676113Y.0000000081 Published online: 04 Nov 2015.Submit your article to this journal View related articles  Fabrication and characterisation of borondoped barium stabilised bismuth cobalt oxidenanocrystalline ceramic composite I˙. Uslu 1 , E. C¸ınar  2 , S. Koc¸yig˘it * 1,3 , A. Aytimur  1,3 and A. Akdemir  2 In this paper, the fabrication and characterisation processes of both boron doped and undopedbarium stabilised bismuth cobalt oxide nanocrystalline ceramic powders using polymericprecursor were reported. Obtained boron doped barium stabilised bismuth cobalt oxidenanocrystalline ceramic powders, which have been synthesised by polymeric precursortechnique at temperatures below 900 u C and at atmospheric condition, were characterised byX-ray diffraction, Fourier transform infrared and scanning electron microscopy techniques.According to X-ray results, fcc and bcc phases coexist in the samples of the nanocrystallineceramic powders. Crystallite sizes for body centred cubic structure were calculated usingScherrer equation for both boron doped and undoped samples. In addition, lattice parameterswere calculated for all samples. Keywords:  Bismuth cobalt oxide, Ceramics, Nanostructured materials, Sol–gel, Polymer precursor Introduction Recently, oxide systems such as barium stabilisedbismuth cobalt oxide ceramic powders have attractedincreasing attention and have been revealed to havepotential as a thermoelectric material because BaO wasobserved as having the lowest transition temperatureand one of the highest ionic conductivities of the Bi 2 O 3 based systems. 1–6 In addition, the addition of B 2 O 3 ,which forms a network structure, creates Bi 2 O 3  basedceramic powders with a higher melting point and agreater ability to withstand temperature changes. 5–8 Bi 2 O 3  based ceramic powders were conventionallyprepared by solid state reaction process, where a mixturecontaining bismuth, barium and cobalt oxides was ballmilled and finally calcined at desired temperature. 9 Thisconventional ceramic preparation technique usuallyleads to inevitable particle coarsening and aggregationof the fabricated powder. The presence of agglomerateswill also result in poor microstructure and properties.Many efforts have been made to avoid this problem. Thepolymer precursor technique has been proven to be oneof the suitable techniques for the preparation of composite oxide, which employs complexing of metalacetate/nitrate precursor in a polymer solution, forexample, polyvinyl alcohol (PVA). The formation of low cost resultant polymeric product is calcined at ahigh temperature to remove the polymer and obtainhomogeneous and unagglomerated crystalline ceramicpowders. The main advantages of polymeric precursortechniques (PPTs) are the homogeneity of the pre-cursors on a molecular level and the low processingtemperatures. 10–17 To the best of our knowledge, we are here for the firsttime reporting fabrication of boron doped bariumstabilised bismuth cobalt oxide ceramic powders atlow temperature under 900 u C and investigating thecrystallisation behaviour and structural changes of thefinal composite Bi 2 O 3  based ceramic nanocrystallinestructure. Experimental In the experiments, PVA (average  M  w  of 85 000– 124 000 g mol 2 1 ), bismuth(III) acetate and bariumacetate were obtained from Sigma Aldrich, andcobalt(II) acetate and boric acid were obtained fromMerck. Ultrapure deionised water was used as a solvent.An aqueous PVA solution (10%) was first prepared bydissolving PVA powder in distilled water and heating at80 u C with stirring for 3 h, and then cooling to roomtemperature. In the experiments, three hybrid polymersolutions were prepared. As a general process, properamounts of bismuth(III) acetate, barium acetate,cobalt(II) acetate and boric acid were added drop bydrop to the 20 g aqueous PVA (10%) solution at 60 u Cseparately ( see  Table 1). The solution was vigorouslystirred for 1 h at this temperature. Stirring wascontinued for 3 h at room temperature. Finally, viscousgels of both boron doped and undoped PVA/Bi–Ba–Coacetate hybrid polymer solutions were obtained.Obtained solutions were poured into ceramic crucibles 1 Department of Chemical Education, Gazi Faculty of Education, GaziUniversity, Teknikokullar, Ankara 06500, Turkey 2 Department of Mechanical Engineering, Faculty of Engineering &Architecture, Selc¸uk University, Selc¸uklu, Konya 42090, Turkey 3 Department of Advanced Technologies, Institute of Science andTechnology, Gazi University, Teknikokullar, Ankara 06500, Turkey * Corresponding author, email sergas_29@hotmail.com  2013 Institute of Materials, Minerals and Mining Published by Maney on behalf of the InstituteReceived 6 December 2012; accepted 29 March 2013 336  Advances in Applied Ceramics  2013  VOL  112  NO  6  DOI 10.1179/1743676113Y.0000000081    D  o  w  n   l  o  a   d  e   d   b  y   [   G  a  z   i   U  n   i  v  e  r  s   i   t  y   ]  a   t   0   7  :   5   5   2   3   J  a  n  u  a  r  y   2   0   1   6  and then calcined at 850 u C for 2 h. Resulting oxideceramic composites obtained from solutions 1 to 3,named as PPT-1 to PPT-3, were ground into powderusing a mortar. Prepared solutions and values of solution components are given in Table 1.The pH and conductivity of the solutions were mea-sured using Wissenschaftlich-Technische-Werksta¨ttenWTW and 315i/SET apparatus. The viscosity of thehybrid polymer solutions was measured with an ANDSV-10 viscometer. The surface tension of the complexhybrid polymer solutions was measured using KRUSSmodel manual measuring system. The crystal structuresof the calcined powders were investigated by means of X-ray diffraction (XRD) (Ultima-IV XRD; Rigaku,Tokyo, Japan) with Cu  K  a 1  radiation at 40 kV and30 mA and graphite monochromator. Results and discussion The pH, viscosity, conductivity and surface tension of the PVA/Bi–Ba–Co acetate solution were measured andgiven in Table 2.The XRD patterns shown in Fig. 1 reveal that theboron doped barium stabilised bismuth cobalt oxide wasformed at the calcination temperatures of 850 u C.Barium oxide stabilised body centred cubic bismuthcobalt oxide structure was identified with eight diffrac-tion peaks that appeared at 2 h  values and associatedplanes of 24 ? 01 u  (220), 28 ? 04 u  (310), 32 ? 81 u  (321), 42 ? 14 u (332), 44 ? 94 u  (431), 54 ? 32 u  (600), 55 ? 67 u  (611) and 58 ? 10 u (620). According to Joint Committee on Powder Diffra-ction Standards International Center for DiffractionData [Joint Committee on Powder Diffraction Stan-dards files 01-074-1228 for the BaO fcc phase and 01-082-1322 for the (Bi 24 2 x Co x )Co 2 2 a O 40  bcc phase], thesepeaks are in good agreement with Fig. 1.X-ray diffraction peaks became sharper with increas-ing boron content in the samples, and full width at half maximum decreased. Therefore, boron doping resultedin a progressive increase in the bcc crystallite size,indicating the crystallinity and stability of the bariumstabilised Bi 2 O 3  –CoO 2  system. This trend is in accor-dance with the SEM results given below. The crystalstructure directly affects the mechanical and electricalproperties of the composite material. 18 As an example,the hardness and strength increase with the increasingamount of bcc phases, but the composite ceramicmaterial gets brittle. It is certainly important to be ableto control the formation of the bcc phases in thecomposite material. 18–21 The crystallite size  D  was calculated based upon themain diffraction peaks’ broadening in the XRD patternusing the Scherrer formula. 22–26 The lattice parametersof the composite samples were determined by comparing Table 2 Physical properties of polymer solutions Solution no. pH Conductivity/mS cm 2 1  Viscosity/mPa s Surface tension/mN m 2 1 PPT-1 3.72 12.07 45.7 53PPT-2 3.61 11.38 38.9 50PPT-3 3.66 11.93 41.1 51 1 X-ray diffraction patterns of crystalline structure of cal-cined boron doped and undoped barium stabilised Bi– Co nanoceramic powders:  a   PPT-1;  b   PPT-2;  c   PPT-3nanocrystalline powder samplesTable 1 Value of polymer solution components Solution no. Equation Value of components/gBismuth acetate Barium acetate Cobalt acetate Boric acid PVA solution (10%) PPT-1 Bi 2 Ba 3 Co 2 O c  2 1.9845 1.2902 … 20PPT-2 Bi 2 Ba 3 Co 2 O c B 0 ? 1  2 1.9845 1.2902 0.0160 20PPT-3 Bi 2 Ba 3 Co 2 O c B 0 ? 5  2 1.9845 1.2902 0.0800 20 2 Fourier transform infrared spectra of  a   PPT-1,  b   PPT-2and  c   PPT-3 nanocrystalline powder samples Uslu et al.  Bismuth cobalt oxide nanocrystalline ceramic composite  Advances in Applied Ceramics  2013  VOL  112  NO  6  337    D  o  w  n   l  o  a   d  e   d   b  y   [   G  a  z   i   U  n   i  v  e  r  s   i   t  y   ]  a   t   0   7  :   5   5   2   3   J  a  n  u  a  r  y   2   0   1   6  the peak positions (2 h ) of the XRD patterns using thebelow relations 27 1 d  2 ~ h 2 z l  2 z k  2 a 2  (2)The calculated structural parameters of the compositesamples for the bcc phase were given in Table 3.According to the calculation results, average structurallattice parameters  a  of the bcc phase for the mainreflection (310) peak were given as 10 ? 0546, 10 ? 0371 and10 ? 0546 nm for the PPT-1, PPT-2 and PPT-3 samplesrespectively. Crystallite sizes  D  were calculated for themain reflection (310) peak using equation (1) as 23, 57and 48 nm for PPT-1, PPT-2 and PPT-3 respectively.The Fourier transform infrared (FTIR) spectra of thebarium stabilised Bi–Co oxide nanocrystalline ceramicpowders were given in Fig. 2. Absorption of IR below610 cm 2 1 is attributed to various modes of Bi–Ovibration in BiO 6 . As mentioned by Cong  et al. , theband at 664 cm 2 1 is attributed to Co–O stretching. Theabsorption band at 692 cm 2 1 is attributed to thebismuth oxide. At 855 cm 2 1 , Bi–O stretching vibrationshave been observed for all samples. The band at765 cm 2 1 is assigned to the B–O–B bending vibrationof bridges containing one trigonal and one tetrahedralboron and has approximately the same intensity for allthe compositional range. At 1200 cm 2 1 , B–O stretchingvibration of trigonal BO 3  units has been observed. The Table 3 Calculated structural parameters for bcc phase Sample (   hkl   )  2 h  /  u  Full width at half maximum/  u  d   /nm  a  /nm  D  /nm  d  /  6 10 2 11 cm 2 2 e  /  6 10 2 3 PPT-1 (220) 24.01 0.2206 3.7033 10.4746(310) 28.04 0.3602 3.1796 10.0546 23 1.9352 2.7974PPT-2 (220) 24.01 0.1239 3.7033 10.4746(310) 28.09 0.1433 3.1740 10.0371 57 0.3062 1.1108PPT-3 (220) 23.96 0.1378 3.7109 10.4961(310) 28.04 0.1715 3.1796 10.0546 48 0.4387 1.3319 3 Scanning electron microscopy analysis shows that more severe agglomeration occurred in PPT-1 samples (undopedboron)4 Images (SEM) show that B 2 O 3  is effective calcining aid and boron doping leads to plate-like grain formation in PPT-2sample Uslu et al.  Bismuth cobalt oxide nanocrystalline ceramic composite 338  Advances in Applied Ceramics  2013  VOL  112  NO  6    D  o  w  n   l  o  a   d  e   d   b  y   [   G  a  z   i   U  n   i  v  e  r  s   i   t  y   ]  a   t   0   7  :   5   5   2   3   J  a  n  u  a  r  y   2   0   1   6  absorption band at 1414 cm 2 1 is thought to arise due tobismuth oxide, cobalt oxide or barium oxide. 5,6,28–30 Figure 3 presents the SEM images of boron undopedbarium stabilised bismuth cobalt oxide nanocrystallineceramic composite (PPT-1). As can be seen, the sampleshave a granular structure of spherical grains with ahomogeneous mean grain size in the order of 60–80 nmfor both materials. These values are in agreement withthe XRD data.Figures 4 and 5 exhibit the SEM images of borondoped barium stabilised bismuth cobalt oxide ceramiccomposite (PPT-2). Plate-like grains were found in thesample possibly due to the anisotropic crystal structureon account of the anisotropic growth behaviour of suchmaterials. It is known that plate-like grain formationis a typical characteristic of bismuth layer structuredcomposite. 31 Conclusion Consequently, in this paper, we report the fabricationand characterisation of a bismuth oxide. Polymericprecursor technique is an alternative chemical methodthat allows for the fabrication of boron doped bariumstabilised Bi–Co oxide nanocrystalline ceramic compo-site using precursors such as metal nitrates, acetates orcarbonates. Obtained boron doped barium stabilisedbismuth cobalt oxide nanocrystalline ceramic powders,which have been synthesised by PPT at temperaturesbelow 900 u C and at atmospheric condition, werecharacterised by XRD, FTIR and SEM techniques.According to X-ray results, fcc and bcc phases coexist inthe samples of the nanocrystalline ceramic powders.Crystallite sizes for body centred cubic structure werecalculated as 23, 57 and 48 nm for PPT-1, PPT-2 andPPT-3 respectively using Scherrer equation. In addition,lattice parameters were calculated as 10 ? 0546, 10 ? 0371and 10 ? 0546 nm for the PPT-1, PPT-2 and PPT-3samples respectively. References 1. T. Suzuki, Y. Dansui, T. Shirai and C. Tsubaki: ‘Defect structureand electrical conductivity in rapidly-quenched and slowly-cooledrhombohedral solid solutions of the system Bi 2 O 3  –BaO’,  J. Mater.Sci. , 1985,  20 , 3125–3130.2. N. M. Sammes, G. A. Tompsett, H. Naefe and F. Aldinger:‘Bismuth based oxide electrolytes – structure and ionic conductiv-ity’,  J. Eur. Ceram. Soc. , 1999,  19 , 1801–1826.3. J. M. Tarascon, R. Ramesh, P. Barboux, M. S. Hedge, G. W. Hull,L. H. Greene, M. Giroud, Y. LePage, W. R. McKinnon, J. V.Waszczak and L. F. Schneemeyer: ‘New non-superconductinglayered Bi-oxide phases of formula Bi 2 M 3 Co 2 O y  containing Coinstead of Cu’,  Solid State Commun. , 1989,  71 , 663–668.4. M. Hervieu, A. Maignan, C. Michel, V. Hardy, N. Cre´on andB. Raveau: ‘Metallicity and thermopower of the misfit cobaltite[Bi 2 Ba 1.8 Co 0.2 O 4 ](RS)[CoO 2 ](2)’,  Phys. Rev. B  , 2003,  67B , 045112.5. T. Tunc, I. Uslu, S. Durmusoglu, S. Keskin, A. Aytimur andA. Akdemir: ‘Synthesis and properties of boron doped Na x Co 2 O 4 nanocrystalline ceramics’,  J. Inorg. Organomet. Polym. , 2012,  22 ,105–112.6. S. Durmusoglu, I. Uslu, T. Tunc, S. Keskin, A. Aytimur andA. Akdemir: ‘Synthesis and characterization of boron-dopedBi 2 O 3  –La 2 O 3  fiber derived nanocomposite precursor’,  J. Polym.Res. , 2011,  18 , 1999–2004.7. S. E. Vankirk and S. W. Martin: ‘Preparation and characterizationof high-density PBO–BI 2 O 3  –B 2 O 3  glasses’,  J. Am. Ceram. Soc. ,1992,  75 , 1028–1031.8. B. Karthikeyan and S. Mohan: ‘Structural, optical and glasstransition studies on Nd 3 z -doped lead bismuth borate glasses’, Physica B  , 2003,  334B , 298–302.9. M. Villegas, A. C. Caballero, C. Moure, P. Duran and J. F.Fernandez: ‘Factors affecting the electrical conductivity of donor-doped Bi 4 Ti 3 O 12  piezoelectric ceramics’,  J. Am. Ceram. Soc. , 1999, 82 , 2411–2416.10. R. Riedel, G. Mera, R. Hauser and A. Klonczynski: ‘Silicon-basedpolymer-derived ceramics: synthesis properties and applications – areview’,  J. Ceram. Soc. Jpn , 2006,  114 , 425–444.11. M. A. Schiavon, K. J. Ciuffi and I. V. P. Yoshida: ‘Glasses in theSi–O–C–N system produced by pyrolysis of polycyclic silazane/siloxane networks’,  J. Non-Cryst. Solids , 2007,  353 , 2280–2288.12. M. A. Schiavon and I. V. P. Yoshida: ‘Ceramic matrix compositesderived from CrSi 2 -filled silicone polycyclic network’,  J. Mater.Sci. , 2004,  39 , 4507–4514.13. M. Takeyama and C. T. Liu: ‘Effects of grain-size and testtemperature on ductility and fracture-behaviour of a B-dopedNi 3 Al alloy’,  Acta Mater. , 1988,  36 , 1241–1249. 5 Images (SEM) show that grain size tends to becomesmall and uniform when boron doping decreasesagglomeration and grain sizes considerably (PPT-3) Uslu et al.  Bismuth cobalt oxide nanocrystalline ceramic composite  Advances in Applied Ceramics  2013  VOL  112  NO  6  339    D  o  w  n   l  o  a   d  e   d   b  y   [   G  a  z   i   U  n   i  v  e  r  s   i   t  y   ]  a   t   0   7  :   5   5   2   3   J  a  n  u  a  r  y   2   0   1   6
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