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Dokonano analizy właściwości elektrycznych, elektrochemicznych i mechanicznych kompozytowych elek... more Dokonano analizy właściwości elektrycznych, elektrochemicznych i mechanicznych kompozytowych elektrolitów tlenkowych, a także membran o mieszanym (jonowo-elektronowym) przewodnictwie elektrycznym pod kątem poprawy parametrów pracy stałotlenkowych ogniw paliwowych (SOFC) czy reaktorów do wytwarzania gazu syntezowego w porównaniu do tworzyw jednofazowych. Dodatek wtrąceń Al2O3 do osnowy przewodnika jonowego 8% mol Y2O3 w ZrO2 (8YSZ) powoduje niewielki wzrost przewodnictwa jonowego tego materiału w temperaturach 500800°C, a także prowadzi do polepszenia właściwości mechanicznych. Znaczny wzrost odporności na kruche pękanie zanotowano dla kompozytowych spieków 8YSZ zawierających wtrącenia Nd2Ti2O7. Poprawa właściwości mechanicznych elektrolitu 8YSZ jest cechą korzystną w aspekcie zastosowania go jako elementu konstrukcyjnego do budowy większości urządzeń elektrochemicznych. Wzrost składowej przewodnictwa elektronowego w elektrolitach cerowych przy niskich prężnościach tlenu prowadzi do spadku efektywności pracy ogniw SOFC. Projektowanie gradientowych elektrolitów tlenkowych Ce0,8Sm0,2O2-Bi0,8Eb0,2O2 lub hybrydowych zbudowanych z przewodnika protonowego BaCe0,8Y0,2O3 i przewodnika jonów tlenu, np. Ce0,8M0,2O2, M = Sm, Gd, powoduje poprawę stabilności tych materiałów w redukujących atmosferach gazowych. Stałotlenkowe ogniwa paliwowe (SOFC) z tymi elektrolitami posiadają znacznie lepsze parametry pracy niż te same ogniwa, lecz zawierające tylko elektrolit cerowy. Kompozytowe ceramiczne membrany o jonowo-elektronowym przewodnictwie w układzie Ce0,8Sm0,2O2-La0,8Sr0,2CrO3 czy Ce0,8Sm0,2O2-CoFe2O4 wydają się być perspektywicznymi tworzywami do konstrukcji reaktorów chemicznych przeznaczonych do wytwarzania gazu syntezowego. Podstawowymi zaletami tych kompozytów oprócz zdolności do transportu strumienia tlenu są także stabilność chemiczna i termiczna podczas długotrwałej pracy w warunkach znacznego gradientu ciśnień tlenu. Słowa kluczowe: energetyka wodorowa, elektrolity tlenkowe, przewodniki protonowe, stałotlenkowe ogniwa paliwowe, gaz syntezowy COMPOSITE IONIC OR IONIC-ELECTRONIC CONDUCTORS INVOLVING CeO2 OR ZrO2 FOR HYDROGEN ENERGY This work is focused on the comparative analysis of electrical, electrochemical and mechanical properties of composite ceramic oxide electrolytes or composite mixed (ionic-electronic) oxide membranes providing a brief overview of the materials having better performance than monophase ones in solid oxide fuel cells or electrochemical reactors for syngas production. Introduction of Al2O3 inclusions into 8% mol Y2O3 in ZrO2 (8YSZ) matrix, caused small improvement of ionic conductivity in the temperature range 500800°C and also lead to improvement of mechanical properties compared to pure 8YSZ. The Nd2Ti2O7 secondary phase was also able to coexist with 8YSZ matrix and the fracture toughness KIc of 8YSZ ceramics was also significantly improved by Nd2Ti2O7 addition. The improvement of mechanical properties of 8YSZ electrolyte is a important feature for application of this material in electrochemical devices. The increase of electronic conductivity in ceria-based electrolytes in low oxygen partial pressure caused the decrease of solid oxide fuel cell performance. On the other hand composite layered ceramics involving Ce0.8Sm0.2O2/Bi0.8Eb0.2O2 or Ce0.9Gd0.1O2/BaCe0.8Y0.2O3/Ce0.9-Gd0.1O1.95 system exhibited better electrolytic stability in gas atmospheres with low oxygen partial pressure at the temperatures 600800°C. These materials are successfully tested as electrolytes in solid oxide fuel cells. The gradient ceramic oxide electrolytes seems to overcome the limitation of applying them as solid electrolytes in solid oxide fuel cells for long time performance. The design of gradient solid oxide electrolytes in the Ce0.8Sm0.2O2-Bi0.8Eb0.2O2 system or hybrid composite electrolytes involving BaCe0.8Y0.2O3 as a proton ionic conductor and Ce0.8M0.2O2, M = Sm, Gd as a oxygen ionic conductor caused the improvement of chemical stability of this material in reducing gas atmospheres. The solid oxide fuel cells involving such composite electrolytes have a much better parameters of performance than the same solid oxide fuel cell involving only ceriabased electrolytes. The dense composite ceramic membrane made of mixed oxygen ion and electron conducting oxides Ce 0.8Sm0.2O2-La0.8Sr0.2CrO3 or Ce0.8Sm0.2O2-CoFe2O4 seem to be perspective materials for electrochemical reactors for partial methane oxidation (POM). The main advantages of such composites are only considerable amounts of oxygen permeation flux but also chemical and thermal stability in long-term performance in reactor conditions.
International Journal of Electrochemical Science
Raw wood chips from beech and acacia were chosen as a source of solid carbon fuels for utilizatio... more Raw wood chips from beech and acacia were chosen as a source of solid carbon fuels for utilization in tubular solid oxide fuel cells. These materials are typical wood waste products from carpentry in Poland. The physicochemical properties of carbon particles produced in situ during the operation of tubular direct carbon oxide fuel cells were determined by different analytical methods. It was found that solid carbon fuel had possessed high carbon content. Based upon structural investigations (X-ray diffraction analysis, Raman spectroscopy), it was found that disordered carbon or highly defected particles had been formed from raw waste wood during the operation of the fuel cell. No products of possible chemical reactions between carbon solid carbon fuel, or evaluated gases and nickel-ceria anodes, were observed during the start-up and operation of the DC-SOFC. It was found through electrochemical investigations that the power output of the DC-SOFC in question was ca. 100 mW/cm 2 at 800°C, which was similar to the performance of a DC-SOFC supplied with activated charcoals. A proposal of the construction of a small stack of tubular solid oxide fuel cells fed with biochar-based fuel was mentioned.
Journal of Solid State Electrochemistry, 2014
Silver-Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathodes were prepared in two ways. In the first ... more Silver-Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathodes were prepared in two ways. In the first method, Ag-BSCF composite powder was prepared in ethanol solution, where Ag nanoparticles serving as a component in the preparation of Ag-BSCF composite cathodes had been previously obtained via one-step synthesis in absolute ethanol using a neutral polymer (polyvinylpyrrolidone). To the best of our knowledge, this is the first study to use a Ag sol obtained by the above method for preparation of Ag-BSCF composite powder. Then, a paste containing this powder was screen-printed on a Sm 0.2 Ce 0.8 O 1.9 electrolyte and sintered at 1,000°C. In the second technique, an aqueous solution of AgNO 3 was added to a previously sintered BSCF cathode, which was then sintered again at 800°C. The oxygen reduction reaction at the quasi-point BSCF cathode on the Sm 0.2 Ce 0.8 O 1.9 electrolyte was tested by electrochemical impedance spectroscopy at different oxygen concentrations in three electrode setup. The continuous decrease of polarization resistance was observed under polarization −0.5 V at 600°C. The comparative studies of both obtained composite Ag-BSCF materials were performed in hydrogen-oxygen IT-SOFC involving samariadoped ceria as an electrolyte and Ni-Gd 0.2 Ce 0.8 O 1.9 anode. In both cases, the addition of silver to the cathode caused an increase in current and power density compared with an IT-SOFC built with the same components but involving a monophase BSFC cathode material.
Some observations on synthesis and electrolytic properties of nonstoichiometric calcium zirconate
Journal of Alloys and Compounds, 2009
Stoichiometric CaZrO3 (CZ-50) and CaZrO3 doped with excess CaO (CZ-51) powders, whose formula (Ca... more Stoichiometric CaZrO3 (CZ-50) and CaZrO3 doped with excess CaO (CZ-51) powders, whose formula (CaO)1−x(ZrO2)x, where x=50 or 51mol.% CaO was successfully synthesised by the co-precipitation calcination method with a saturated solution of (NH4)2C2O4 in concentrated NH3 solution as a precipitation agent. The thermal evolution of CaZrO3 dried precursor during heating them up to 1200°C was monitored by thermal (DTA, TG)
1 August 2012 Development of direct carbon fuel cells opens new options for utlization of various... more 1 August 2012 Development of direct carbon fuel cells opens new options for utlization of various carbonaceous fuels to produce electricity. Moreover, even some waste materials and by-products from industrial processes appear to be suitable for conversion in DCFC. An attractive opportunity is the use of carbon based by-products of methane plasma dissociation as a fuel. In this work comprehensive studies of two types of carbon fuels were performed, namely carbon powder (carbon A) produced by methane plasma dissociation and comercially available carbon black powder (carbon B). Before the electrochemical testing, both carbon fuels were characterized by X-ray, Raman, XPS/ESCA spectroscopy, thermal analysis (DTA,TG), electrical conductivity and other methods. Carbon A possessed larger particle surface area and lower ohmic resistance than carbon B, its purity was comparably high and ash content was low. Four different types of DCFCs were used during testing: all of them used solid electro...
Advances in Materials Sciences, 2011
The Ca 0.95 Mg 0.05 ZrO 3 nanopowder was successfully synthesized by the citrate method. The XRD ... more The Ca 0.95 Mg 0.05 ZrO 3 nanopowder was successfully synthesized by the citrate method. The XRD diffraction method evaluated that the orthorombic CaZrO 3 phase was detected in powders or sintered samples. The sintered sample at 1450 o C for 2 hours exhibits about 98 % of theoretical density. The electrical conductivity was measured by a.c impedance spectroscopy method in the temperature range of 200-800 o C. The transference oxygen ion number of CaZrO 3 sample was estimated from electromotive force measurements (E m) of galvanic cell in the temperature range of 550-1100 o C. The Ca 0.95 Mg 0.05 ZrO 3 exhibits purely oxygen ion conductivity. It was successfully applied as a solid electrolyte in the electrochemical oxygen sensor operating at 660 o C. The measured electromotive force of investigated cell was found to be linear with the logarithm of oxygen partial pressure in the range of 10-6 atm 1 atm and in the temperature range of 660-1000 o C.
Advances in Materials Sciences, 2008
This work is focused on the comparative analysis of electrical, electrochemical and mechanical pr... more This work is focused on the comparative analysis of electrical, electrochemical and mechanical properties of composite ceramic oxide electrolytes, providing a brief overview of the materials having better performance than monophase ones in various high temperature electrochemical devices such as: solid oxide fuel cells, sensors for automotive industry, oxygen probes for controlling metal processing. Introduction of Al 2 O 3 inclusions into cubic yttria-zirconia solid solution (8YSZ) matrix, caused the improvement of electrical and mechanical properties compared to pure 8YSZ. The Nd 2 Ti 2 O 7 secondary phase was also able to coexist with 8YSZ matrix and the fracture toughness K Ic of 8YSZ ceramics was also significantly improved by Nd 2 Ti 2 O 7 addition. Heterophase oxide ionic conductors in the system Calcium zirconate-cubic calcia zirconia solid electrolytes seem to be promising solid electrolytes for application in electrochemical probes for controlling oxygen dissolved in molten steel. The ionic conduction limit for electrolytes based on CaZrO 3 is lower than that for calcia-stabilized zirconia (13CSZ). Hence CaZrO 3-based materials perform better at low oxygen concentration at molten alloys. On the other hand composite layered ceramics involving Ce 0.8 Sm 0.2 O 2 /Bi 0.8 Eb 0.2 O 2 or Ce 0.9 Gd 0.1 O 2 /BaCe 0.8 Y 0.2 O 3 /Ce 0.9 Gd 0.1 O 1.95 system exhibited better electrolytic stability in gas atmospheres with low oxygen partial pressure at the temperatures 600-800 o C. These materials are successfully tested as electrolytes in solid oxide fuel cells. The gradient ceramic oxide electrolytes seems to overcome the limitation of applying them as solid electrolytes in solid oxide fuel cells for long time performance.
Journal of Solid State Electrochemistry, 2010
The aim of this work was to study the electrical and electrochemical properties of the (Ba 1−x Ca... more The aim of this work was to study the electrical and electrochemical properties of the (Ba 1−x Ca x)(Zr 0.9 Y 0.1) O 3 solid solutions. The powders of different calcium content (x=0, 0.05, 0.1, and 1) were prepared by a thermal decomposition of organo-metallic precursors containing ethylenediaminetetraacetate acid. X-ray diffraction analysis showed that a small substitution of calcium for barium caused formation of cubic solid solutions with the decreasing cell parameters. Electrical conductivity measurements were performed by the d.c. four-probe method in controlled gas atmospheres containing Ar, air, H 2 , and/or H 2 O at temperature from 300 to 800°C. It was found that the conductivity depended on a chemical composition of the samples and the atmosphere. Overall, the electrical conductivity was higher in wet atmospheres that contained oxygen that was in accordance with the model of a proton transport in perovskite structure which assumed the presence of the oxygen vacancies. The solid solution containing 5 mol% of calcium showed the highest conductivity and the lowest activation energy of conductivity regardless of the atmospheres; this can be attributed to the local changes in the cubic perovskite structure. Test results for CaZr 0.9 Y 0.1 O 3 used as an electrolyte in solid oxide galvanic cells involving CaCr 2 O 4 as a reference electrode are also reported.
Dokonano analizy właściwości elektrycznych, elektrochemicznych i mechanicznych kompozytowych elek... more Dokonano analizy właściwości elektrycznych, elektrochemicznych i mechanicznych kompozytowych elektrolitów tlenkowych, a także membran o mieszanym (jonowo-elektronowym) przewodnictwie elektrycznym pod kątem poprawy parametrów pracy stałotlenkowych ogniw paliwowych (SOFC) czy reaktorów do wytwarzania gazu syntezowego w porównaniu do tworzyw jednofazowych. Dodatek wtrąceń Al2O3 do osnowy przewodnika jonowego 8% mol Y2O3 w ZrO2 (8YSZ) powoduje niewielki wzrost przewodnictwa jonowego tego materiału w temperaturach 500800°C, a także prowadzi do polepszenia właściwości mechanicznych. Znaczny wzrost odporności na kruche pękanie zanotowano dla kompozytowych spieków 8YSZ zawierających wtrącenia Nd2Ti2O7. Poprawa właściwości mechanicznych elektrolitu 8YSZ jest cechą korzystną w aspekcie zastosowania go jako elementu konstrukcyjnego do budowy większości urządzeń elektrochemicznych. Wzrost składowej przewodnictwa elektronowego w elektrolitach cerowych przy niskich prężnościach tlenu prowadzi do spadku efektywności pracy ogniw SOFC. Projektowanie gradientowych elektrolitów tlenkowych Ce0,8Sm0,2O2-Bi0,8Eb0,2O2 lub hybrydowych zbudowanych z przewodnika protonowego BaCe0,8Y0,2O3 i przewodnika jonów tlenu, np. Ce0,8M0,2O2, M = Sm, Gd, powoduje poprawę stabilności tych materiałów w redukujących atmosferach gazowych. Stałotlenkowe ogniwa paliwowe (SOFC) z tymi elektrolitami posiadają znacznie lepsze parametry pracy niż te same ogniwa, lecz zawierające tylko elektrolit cerowy. Kompozytowe ceramiczne membrany o jonowo-elektronowym przewodnictwie w układzie Ce0,8Sm0,2O2-La0,8Sr0,2CrO3 czy Ce0,8Sm0,2O2-CoFe2O4 wydają się być perspektywicznymi tworzywami do konstrukcji reaktorów chemicznych przeznaczonych do wytwarzania gazu syntezowego. Podstawowymi zaletami tych kompozytów oprócz zdolności do transportu strumienia tlenu są także stabilność chemiczna i termiczna podczas długotrwałej pracy w warunkach znacznego gradientu ciśnień tlenu. Słowa kluczowe: energetyka wodorowa, elektrolity tlenkowe, przewodniki protonowe, stałotlenkowe ogniwa paliwowe, gaz syntezowy COMPOSITE IONIC OR IONIC-ELECTRONIC CONDUCTORS INVOLVING CeO2 OR ZrO2 FOR HYDROGEN ENERGY This work is focused on the comparative analysis of electrical, electrochemical and mechanical properties of composite ceramic oxide electrolytes or composite mixed (ionic-electronic) oxide membranes providing a brief overview of the materials having better performance than monophase ones in solid oxide fuel cells or electrochemical reactors for syngas production. Introduction of Al2O3 inclusions into 8% mol Y2O3 in ZrO2 (8YSZ) matrix, caused small improvement of ionic conductivity in the temperature range 500800°C and also lead to improvement of mechanical properties compared to pure 8YSZ. The Nd2Ti2O7 secondary phase was also able to coexist with 8YSZ matrix and the fracture toughness KIc of 8YSZ ceramics was also significantly improved by Nd2Ti2O7 addition. The improvement of mechanical properties of 8YSZ electrolyte is a important feature for application of this material in electrochemical devices. The increase of electronic conductivity in ceria-based electrolytes in low oxygen partial pressure caused the decrease of solid oxide fuel cell performance. On the other hand composite layered ceramics involving Ce0.8Sm0.2O2/Bi0.8Eb0.2O2 or Ce0.9Gd0.1O2/BaCe0.8Y0.2O3/Ce0.9-Gd0.1O1.95 system exhibited better electrolytic stability in gas atmospheres with low oxygen partial pressure at the temperatures 600800°C. These materials are successfully tested as electrolytes in solid oxide fuel cells. The gradient ceramic oxide electrolytes seems to overcome the limitation of applying them as solid electrolytes in solid oxide fuel cells for long time performance. The design of gradient solid oxide electrolytes in the Ce0.8Sm0.2O2-Bi0.8Eb0.2O2 system or hybrid composite electrolytes involving BaCe0.8Y0.2O3 as a proton ionic conductor and Ce0.8M0.2O2, M = Sm, Gd as a oxygen ionic conductor caused the improvement of chemical stability of this material in reducing gas atmospheres. The solid oxide fuel cells involving such composite electrolytes have a much better parameters of performance than the same solid oxide fuel cell involving only ceriabased electrolytes. The dense composite ceramic membrane made of mixed oxygen ion and electron conducting oxides Ce 0.8Sm0.2O2-La0.8Sr0.2CrO3 or Ce0.8Sm0.2O2-CoFe2O4 seem to be perspective materials for electrochemical reactors for partial methane oxidation (POM). The main advantages of such composites are only considerable amounts of oxygen permeation flux but also chemical and thermal stability in long-term performance in reactor conditions.
International Journal of Electrochemical Science
Raw wood chips from beech and acacia were chosen as a source of solid carbon fuels for utilizatio... more Raw wood chips from beech and acacia were chosen as a source of solid carbon fuels for utilization in tubular solid oxide fuel cells. These materials are typical wood waste products from carpentry in Poland. The physicochemical properties of carbon particles produced in situ during the operation of tubular direct carbon oxide fuel cells were determined by different analytical methods. It was found that solid carbon fuel had possessed high carbon content. Based upon structural investigations (X-ray diffraction analysis, Raman spectroscopy), it was found that disordered carbon or highly defected particles had been formed from raw waste wood during the operation of the fuel cell. No products of possible chemical reactions between carbon solid carbon fuel, or evaluated gases and nickel-ceria anodes, were observed during the start-up and operation of the DC-SOFC. It was found through electrochemical investigations that the power output of the DC-SOFC in question was ca. 100 mW/cm 2 at 800°C, which was similar to the performance of a DC-SOFC supplied with activated charcoals. A proposal of the construction of a small stack of tubular solid oxide fuel cells fed with biochar-based fuel was mentioned.
Journal of Solid State Electrochemistry, 2014
Silver-Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathodes were prepared in two ways. In the first ... more Silver-Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) cathodes were prepared in two ways. In the first method, Ag-BSCF composite powder was prepared in ethanol solution, where Ag nanoparticles serving as a component in the preparation of Ag-BSCF composite cathodes had been previously obtained via one-step synthesis in absolute ethanol using a neutral polymer (polyvinylpyrrolidone). To the best of our knowledge, this is the first study to use a Ag sol obtained by the above method for preparation of Ag-BSCF composite powder. Then, a paste containing this powder was screen-printed on a Sm 0.2 Ce 0.8 O 1.9 electrolyte and sintered at 1,000°C. In the second technique, an aqueous solution of AgNO 3 was added to a previously sintered BSCF cathode, which was then sintered again at 800°C. The oxygen reduction reaction at the quasi-point BSCF cathode on the Sm 0.2 Ce 0.8 O 1.9 electrolyte was tested by electrochemical impedance spectroscopy at different oxygen concentrations in three electrode setup. The continuous decrease of polarization resistance was observed under polarization −0.5 V at 600°C. The comparative studies of both obtained composite Ag-BSCF materials were performed in hydrogen-oxygen IT-SOFC involving samariadoped ceria as an electrolyte and Ni-Gd 0.2 Ce 0.8 O 1.9 anode. In both cases, the addition of silver to the cathode caused an increase in current and power density compared with an IT-SOFC built with the same components but involving a monophase BSFC cathode material.
Some observations on synthesis and electrolytic properties of nonstoichiometric calcium zirconate
Journal of Alloys and Compounds, 2009
Stoichiometric CaZrO3 (CZ-50) and CaZrO3 doped with excess CaO (CZ-51) powders, whose formula (Ca... more Stoichiometric CaZrO3 (CZ-50) and CaZrO3 doped with excess CaO (CZ-51) powders, whose formula (CaO)1−x(ZrO2)x, where x=50 or 51mol.% CaO was successfully synthesised by the co-precipitation calcination method with a saturated solution of (NH4)2C2O4 in concentrated NH3 solution as a precipitation agent. The thermal evolution of CaZrO3 dried precursor during heating them up to 1200°C was monitored by thermal (DTA, TG)
1 August 2012 Development of direct carbon fuel cells opens new options for utlization of various... more 1 August 2012 Development of direct carbon fuel cells opens new options for utlization of various carbonaceous fuels to produce electricity. Moreover, even some waste materials and by-products from industrial processes appear to be suitable for conversion in DCFC. An attractive opportunity is the use of carbon based by-products of methane plasma dissociation as a fuel. In this work comprehensive studies of two types of carbon fuels were performed, namely carbon powder (carbon A) produced by methane plasma dissociation and comercially available carbon black powder (carbon B). Before the electrochemical testing, both carbon fuels were characterized by X-ray, Raman, XPS/ESCA spectroscopy, thermal analysis (DTA,TG), electrical conductivity and other methods. Carbon A possessed larger particle surface area and lower ohmic resistance than carbon B, its purity was comparably high and ash content was low. Four different types of DCFCs were used during testing: all of them used solid electro...
Advances in Materials Sciences, 2011
The Ca 0.95 Mg 0.05 ZrO 3 nanopowder was successfully synthesized by the citrate method. The XRD ... more The Ca 0.95 Mg 0.05 ZrO 3 nanopowder was successfully synthesized by the citrate method. The XRD diffraction method evaluated that the orthorombic CaZrO 3 phase was detected in powders or sintered samples. The sintered sample at 1450 o C for 2 hours exhibits about 98 % of theoretical density. The electrical conductivity was measured by a.c impedance spectroscopy method in the temperature range of 200-800 o C. The transference oxygen ion number of CaZrO 3 sample was estimated from electromotive force measurements (E m) of galvanic cell in the temperature range of 550-1100 o C. The Ca 0.95 Mg 0.05 ZrO 3 exhibits purely oxygen ion conductivity. It was successfully applied as a solid electrolyte in the electrochemical oxygen sensor operating at 660 o C. The measured electromotive force of investigated cell was found to be linear with the logarithm of oxygen partial pressure in the range of 10-6 atm 1 atm and in the temperature range of 660-1000 o C.
Advances in Materials Sciences, 2008
This work is focused on the comparative analysis of electrical, electrochemical and mechanical pr... more This work is focused on the comparative analysis of electrical, electrochemical and mechanical properties of composite ceramic oxide electrolytes, providing a brief overview of the materials having better performance than monophase ones in various high temperature electrochemical devices such as: solid oxide fuel cells, sensors for automotive industry, oxygen probes for controlling metal processing. Introduction of Al 2 O 3 inclusions into cubic yttria-zirconia solid solution (8YSZ) matrix, caused the improvement of electrical and mechanical properties compared to pure 8YSZ. The Nd 2 Ti 2 O 7 secondary phase was also able to coexist with 8YSZ matrix and the fracture toughness K Ic of 8YSZ ceramics was also significantly improved by Nd 2 Ti 2 O 7 addition. Heterophase oxide ionic conductors in the system Calcium zirconate-cubic calcia zirconia solid electrolytes seem to be promising solid electrolytes for application in electrochemical probes for controlling oxygen dissolved in molten steel. The ionic conduction limit for electrolytes based on CaZrO 3 is lower than that for calcia-stabilized zirconia (13CSZ). Hence CaZrO 3-based materials perform better at low oxygen concentration at molten alloys. On the other hand composite layered ceramics involving Ce 0.8 Sm 0.2 O 2 /Bi 0.8 Eb 0.2 O 2 or Ce 0.9 Gd 0.1 O 2 /BaCe 0.8 Y 0.2 O 3 /Ce 0.9 Gd 0.1 O 1.95 system exhibited better electrolytic stability in gas atmospheres with low oxygen partial pressure at the temperatures 600-800 o C. These materials are successfully tested as electrolytes in solid oxide fuel cells. The gradient ceramic oxide electrolytes seems to overcome the limitation of applying them as solid electrolytes in solid oxide fuel cells for long time performance.
Journal of Solid State Electrochemistry, 2010
The aim of this work was to study the electrical and electrochemical properties of the (Ba 1−x Ca... more The aim of this work was to study the electrical and electrochemical properties of the (Ba 1−x Ca x)(Zr 0.9 Y 0.1) O 3 solid solutions. The powders of different calcium content (x=0, 0.05, 0.1, and 1) were prepared by a thermal decomposition of organo-metallic precursors containing ethylenediaminetetraacetate acid. X-ray diffraction analysis showed that a small substitution of calcium for barium caused formation of cubic solid solutions with the decreasing cell parameters. Electrical conductivity measurements were performed by the d.c. four-probe method in controlled gas atmospheres containing Ar, air, H 2 , and/or H 2 O at temperature from 300 to 800°C. It was found that the conductivity depended on a chemical composition of the samples and the atmosphere. Overall, the electrical conductivity was higher in wet atmospheres that contained oxygen that was in accordance with the model of a proton transport in perovskite structure which assumed the presence of the oxygen vacancies. The solid solution containing 5 mol% of calcium showed the highest conductivity and the lowest activation energy of conductivity regardless of the atmospheres; this can be attributed to the local changes in the cubic perovskite structure. Test results for CaZr 0.9 Y 0.1 O 3 used as an electrolyte in solid oxide galvanic cells involving CaCr 2 O 4 as a reference electrode are also reported.