Synthesis and investigation of structural, thermal and electrical properties of the BaZr1-xInx O3-ä (x00.50) perovskite
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Manuscript Num: C_335 Journal Name : ChemXpress Manuscript Title : Synthesis and Investigation of Structural, Thermal and Electrical Properties of the BaZr1xInx O3-δ (x�0�0.50) Perovskite Article Type : Full Paper Corresponding Author : Shahzad
Original Article Synthesis and investigation of structural, thermal and electrical properties of the BaZr1-xInx O3-ä (x00.50) perovskite H.Shahzad1*, M.S.Aktar1, S.M.Yunus1, I.Kamal1, A.K.M.Zakaria1, T.K.Datta1, A.K.Das1, S.Eriksson3, Shafinaz A.Lopa2, M.Abdul Jalil2 1
Institute of Nuclear Science & Technology, Bangladesh Atomic Energy Commission, (BANGLADESH) 2 Department of Electrical & Computer Engineering, Presidency University, 10 Kemal Ataturk Avenue, Banani, Dhaka 1213, (BANGLADESH) 3 Department of Chemical & Biological Engineering, Chalmers University of Technology, (SWEDEN) E-mail:
[email protected];
[email protected]
Abstract : The polycrystalline samples of BaZr1- shifted with increasing Indium concentrations. The TGA InxO3-ä (0.0, 0.10, 0.15, 0.175, 0.20, 0.225, 0.25, 0.27, 0.30 and 0.50) were prepared in the conventional solid state ceramic method in air at 1550°C. The X-ray diffraction experiments were performed on all of the samples. The X-ray diffraction patterns showed sharp Bragg peaks indicating the formation of single phased cubic perovskite structure. The peaks found right
was done for as-prepared x = 0.50 sample from 1007500C and found that a mass loss occurred due to dehydration at higher temperature e.g., T>6000C. The conductivity of the 50% Indium doped sample for various temperature were also measured and it is high in the intermediate temperature range (300-5500C). Global Scientific Inc.
INTRODUCTION
ity and high proton conductivity are the key features for technological application of these materials. The practical application of acceptor doped alkaline earth cerates is, for example, limited by their thermal instability[7]. Acceptor doped zirconates are in general chemically and mechanically more stable than cerates[6]. For oxide systems it has been shown that high symmetry and a large lattice constant are advantageous for the mobility of protonic defects, which plays a role for the selection of proton conducting materials. In this work, the highly symmetric perovskite structure series BaZr1-xInxO3-ä (0.0x0.50) has been studied both as-prepared and
x
To develop efficient solid state proton conducting materials suitable for application at an intermediate temperature range (200-5000C) is a challenge for the scientists[1]. This temperature range is often used both in chemical and energy processing industries. The investigation of proton conductivity in perovskite type materials started more than two and half decades ago, Yb doped SrCeO3[2], Nd doped BaCeO3[3] and Y doped BaZrO3[4-6] are examples of systems that exhibit good proton conducting properties. Thermodynamic stabil-
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Original Article hydrated form. By replacing some of the tetravalent zirconium ions with trivalent indium, oxygen vacancies and also holes may be formed in order to compensate for the change in charge. EXPERIMENTAL
tacts. After coving the surface with Pt paste, the sample was sintered at 10000C for 8 hrs prior to hydration. RESULTS AND DISCUSSION
Figure 1 shows the X-ray diffraction patterns of as-prepared BaZr1-xInxO3-ä (0x0.50) samples. The Ten samples were prepared by traditional solid state diffraction patterns indicate that the samples were highly sintering method. Approximate amount of BaCO3, In2O3 crystalline and no impurity peaks were detected. and ZrO2 have been mixed in order to obtain the deFigure 2 shows the X-ray diffraction patterns of sired BaZr1-xInxO3-ä, where x = 0.0, 0.10, 0.15, 0.175, deuterated BaZr1-xInxO3-ä (0x0.50) samples. In this 0.20, 0.225, 0.25, 0.275, 0.30 and 0.50. To ensure case a set of single phase was obtained for all investithorough mixing, ethanol (99.5%) was added during the gated samples, which clearly indicates that the deuteramilling, which was performed manually using an agate tion reaction has been completed in contrast to the hymortar and pestle. The finely ground material was fired drated sample. As already mentioned in the experimental at 10000C for 8 hours to 24 hours and subsequently part, all the deuteration reactions were carried out at ground and pelletized using a 13 mm diameter die under higher temperature (1850C) with a higher flow rate (1 a pressure of 6 tons. The pellets were (pressure 5-6 L/min) compared with the hydration attempt. tons) were pre-sintered at 12000C and 13500C in air Figure 3 shows the dynamic TGA result for the asfor 48 and 24 hrs respectively and finally reground and prepared x= 0.50 sample. A change in mass was mencompacted under similar conditions and re-fired at tioned during a heating and cooling run under humid con15000C for 24 hrs. After the final sintering the pellets dition (10 vol.% water vapor). During the heating cycle showed a density corresponding to 75% of the theo- mass gain occurred below 3000C, while mass loss started retical value. In order to ensure the removal of as many above 3000C. A step during the heating cycle close to protons as possible from the as-prepared material, the 6000C was observed. This step may be an effect of samples were annealed at 6000C under 2×10-6 mbar rapid heating, or an effect of gas flow fluctuations. Above for 1h. The as-prepared samples were hydrated by an- 7000C no mass change was observed. This indicates nealing the powder at 2500C for 198h in flowing N2 that the vast majority of protons have left the sample saturated at 2200C with air bubble. Later deuteration and further proton up-take is not possible at such high reactions were performed by annealing powder samples temperature even under humid atmosphere. However, 1850C under air flow. The X-ray diffraction measure- during the cooling cycle below 7000C the sample starts ments were carried out at ambient temperature using a to gain the mass under the same atmosphere. Finally, Guinier-Hagg camera (CuKá1 = 1.5406 Å) with sili- the sample regains its hydrated mass, which confirms con (NBS 640b) as internal standard. Then the samples the reversibility of the hydration process. The reversible were vacuum dried at 9500C for 12 hrs. Finally the mass loss/gain under humid atmosphere was about 1.4 samples were deuterated at 1850C for 15-18 hrs. The wt.%[9]. The TGA result for x = 0.50 sample indicates TGA was carried out for as-prepared x = 0.50 sample that a mass loss occurred due to dehydration at higher from 100-7500C with a Sataram TAG 16. To avoid temperature e.g., T>6000C. The conductivity result obcondensation of water, the equipment was kept at 6500C tained at different temperatures and the Arrhenius plot for several hours before transferring the sample into the of hydrated 50% In-doped BaZrO3 is shown in Figure furnace. Heating as well as cooling cycles were made at 4. At lower temperatures (150-3000C) and higher tema rate of 1.50C/min in a stream of Ar gas saturated at peratures (550-9000C) a typical Arrhenius behavior, 6000C with water vapor at a flow rate of 20 ml/min. The where conductivity increases with increasing the temconductivity cell used was ProboStatTM[8]. The oxide perature was observed. In contrast, a plateau was found electrode surface was covered with conducting plati- in temperature range 350-5500C. This plateau can be a num paste and platinum grid to assure good Ohmic con- consequence of an increase in protonic charge mobility
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Original Article and a simultaneous decrease in proton concentration due to a loss of water[10]. The bulk and total conductivity during the heating cycle were 8.7×10-4 S cm-1 b(activation energy 0.40 eV) and 9.0×10-5 S cm-1 (activation energy is 0.63 eV) respectively at 3000C. In comparison, the total con-
ductivity was nearly one order of magnitude lower than that of bulk. Lower conductivity and higher activation energy compared to the bulk may be a result of local structural distortion in the grain boundary region which possibly decreases proton mobility and reduces the proton concentration in the grain boundary region[11].
Figure 1 : X-ray diffraction patterns of as-prepared BaZr1-xInxO3-ä (0x0.50) samples.
Figure 2 : X-ray diffraction pattern of deuterated BaZr1-xInxO3-ä (0x0.50) samples.
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Original Article ACKNOWLEDGEMENTS We give thank specially to Swedish International Development Authority (SIDA) and Swedish Research Council for funding of research, for facilitating collaboration between Chalmers University of Technology and Bangladesh Atomic Energy Commission searching new ceramic materials of Solid Oxide Fuel Cells. REFERENCES
Figure 3 : TGA curve for as-prepared BaZr1-xInxO3-ä, x= 0.50, taken at 1.50C/min under an Argon gas flow saturated with water. : heating cycle and : cooling cycle
Figure 4 : Arrhenius plot of ó for hydrated BaZr1-xInxO3-ä, x= 0.50. : bulk ó, : total ó during heating cycle, : total ó during cooling cycle.
CONCLUSION It was possible to obtain single phase BaZr1-xInxO3(0x0.50) samples by using a standard solid-state ä synthesis route. The XRD scans data showed that all samples posses cubic symmetry. The TGA experiment demonstrated that the maximum water uptake occurs below 3000C. The conductivity was high in the intermediate temperature range (300-5500C).
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