Co-Doping Effect on the Properties of Scandia Stabilized ZrO2

International Journal of Materials Science and Engineering, 2019

Y and Sc co-doped ZrO 2 [Zr 0.84 Y 0.08 Sc 0.08 O 1.92 (4Sc4YSZ)] solid electrolyte was prepared via an alkoxide sol-gel route. 4Sc4YSZ was characterized by TG-DTA, XRD, SEM-EDS and AC impedance spectroscopy. XRD patterns showed that co-doping with Y and Sc resulted to the successful stabilization of the highly conductive cubic phase with a lattice parameter of 5.12 Å. Y and Sc dopants are well-distributed within the ZrO 2 particles as evidenced by EDS elemental maps. Total conductivities from 500 °C to 700 °C were determined from AC impedance spectroscopy and an activation energy of 1.31 eV (500-650 °C) was calculated. Even at a low sintering condition of 1200 °C for 5 h, a promising conductivity of 109 mS/cm was achieved for 4Sc4YSZ at 700 °C which is higher than the conductivity of typical 8YSZ solid electrolyte.

Solid State Ionics, 2014

Scandia-stabilized zirconia (ScSZ) electrolytes exhibit the highest ionic conductivity among all ZrO 2 -based materials. However, a phase transition occurs around 650°C from cubic to rhombohedral β-phase which is unique for Sc-stabilized zirconia and leads to reduced conductivity. The occurrence of this β-phase can be suppressed by co-doping ScSZ. The aims of this study are to confirm the influence of a small amount of Fe 2 O 3 doping on both the stabilization of the cubic phase and the decrease of the sintering temperature and to investigate the influence of this co-doping on the ionic and electronic conductivity of ScSZ. Therefore (ZrO 2 ) 0.90 -(Sc 2 O 3 ) 0.07 -(Fe 2 O 3 ) 0.03 powder has been prepared by precipitation in aqueous solution and sintered at 1380°C to obtain ceramic. The electrical properties (ionic and electronic conductivities) of this ceramic are compared to the ones of Fe-doped YSZ.

Solid State Ionics, 2011

Cubic scandia-stabilised zirconia (ScSZ) has a very high oxygen ion conductivity, significantly higher than the more common yttria-stabilised zirconia (YSZ). However, its practical use is hindered by an ordered rhomboedric phase being present at low temperature which is unique for zirconias. The occurrence of this phase can be suppressed by co-doping scandia-stabilised with ternary metal oxides. It is the aim of this study to investigate the influence of co-doping with various cations on the ionic conductivity, and on the phase transition towards lower temperatures. To do that, we prepared scandia-stabilised zirconia containing 10 mol% Sc 2 O 3 and up to 1.0 mol% Gd 2 O 3 , CaO, or CeO 2 , respectively, using a sol-gel method starting with nitrates of the metals. Powders were sintered at 1500°C to obtain dense material with grain sizes in the range of 0.5 to 1.0 μm. An addition of more than 0.5 mol% Gd 2 O 3 significantly decreased the transition temperature of the phase transition between cubic and rhombohedral. The low temperature AC conductivity, measured in the range of 400 to 950°C, was highest for ScSZ containing 1 mol% CeO 2 . The Arrhenius plot was strongly curved, indicating association or ordering of oxygen vacancies, which were explained with literature models.

Microscopy and Microanalysis, 2013

As the presence of Sc2O3 and CeO2 is known to largely enhance the ionic conductivity in the temperature range of 600–800°C, compared with the conventional yttria-stabilized ZrO2, Sc2O3&CeO2-stabilized ZrO2 provide its applicability as electrolytes in solid oxide fuel cells. The current study introduces the methodology to synthesize Sc2O3&CeO2-stabilized ZrO2 powders by using co-precipitation technique or high-temperature hydrothermal reaction, and further describes the structural characterization of the zirconia powders synthesized by the above-mentioned two methods. The co-precipitation technique was found to allow obtaining powders of cubic phase, whereas high-temperature hydrothermal synthesis results in the presence of a monoclinic phase as well. The scanning transmission electron microscope observations also confirm that the size of the synthesized ZrO2 powders in this study is found to be much smaller than that of commercially available powders.

Journal of Materials Engineering and Performance, 2014

"The effect of Er2O3 addition on electrical conductivity of c-ZrO2 was investigated by analyzing the impedance spectra of undoped and various amounts of Er2O3-doped cubic zirconia (c-ZrO2). The undoped and 1-15 wt% Er2O3-doped c-ZrO2 powders were prepared via colloidal process. The doped powders were then pelletized under a pressure of 200 MPa. In addition, the undoped and Er2O3-doped c-ZrO2 specimens were sintered at 1500 C for 1 h. The electrical conductivity of the specimens was measured using a frequency response analyzer in the frequency range of 100 mHz-13 MHz, in the temperature range of 300- 800 C. Electrical conductivity results indicate an increase in the conductivity with increase in the test temperature. The addition of 1 wt% Er2O3 into c-ZrO2 led to an increase in the grain interior, grain boundary, and total conductivities. The distortion caused by the addition of Er3+ cations in the c-ZrO2 lattice leads to an increase in the concentration of oxygen vacancies in the c-ZrO2 matrix, resulting in an enhancement in the electrical conductivities."

Microscopy and Microanalysis, 2013

As the presence of Sc 2 O 3 and CeO 2 is known to largely enhance the ionic conductivity in the temperature range of 600-8008C, compared with the conventional yttria-stabilized ZrO 2 , Sc 2 O 3 &CeO 2stabilized ZrO 2 provide its applicability as electrolytes in solid oxide fuel cells. The current study introduces the methodology to synthesize Sc 2 O 3 &CeO 2-stabilized ZrO 2 powders by using co-precipitation technique or high-temperature hydrothermal reaction, and further describes the structural characterization of the zirconia powders synthesized by the above-mentioned two methods. The co-precipitation technique was found to allow obtaining powders of cubic phase, whereas high-temperature hydrothermal synthesis results in the presence of a monoclinic phase as well. The scanning transmission electron microscope observations also confirm that the size of the synthesized ZrO 2 powders in this study is found to be much smaller than that of commercially available powders.

French-Ukrainian Journal of Chemistry, 2018

Parameters of the non-Debye relaxation in the 10Sc1CeSZ solid electrolyte made of various types of ZrO2 powder stabilized with 10-mol.% Sc2O3 and 1-mol.% CeO2 were studied. The influence of powder properties and their sintering temperatures on the impedance spectra is analyzed. In regard to electrical response, the polycrystalline ceramic electrolytes may be considered as a single-phase or a two-phase material consisting of a grain bulk and a boundary. In many cases, the boundary resistance is independent practically on dopants and their distribution across the powders and sintering temperatures. The powder compositions suitable for an electrolyte and electrodes are specified.

ECS Transactions, 2008

ZrO 2 :10 mol%Sc 2 O 3 (10ScSZ) powders were synthesized by the polyacrylamide technique (route I) and the polymeric precursor technique (route II). Attrition milling was used to break up powder agglomerates. The evolution of the distribution of particle size upon attrition milling was evaluated by laser scattering. Impedance spectroscopy measurements were carried out in cold-pressed powders in the 500 C-1400 C range during sintering and in the 300-500 C range after sintering. Upon sintering, the decrease of the total electrical resistivity of the specimens prepared with both powders is similar. Nanosize ZrO 2 :10 mol% Sc 2 O 3 powders synthesized by route I are less sinteractive than powders synthesized by route II due to formation of agglomerates, which produce, upon sintering, pellets with intragranular pores. Sintered pellets using powders prepared by route I have lower electrical conductivity than pellets using powders prepared by route II.

Solid State Ionics, 2011

The electrical properties of bulk and grain boundaries of scandia-stabilized zirconia co-doped with yttria and ceria have been determined as a function of temperature (300 b T/°C b 700) and oxygen partial pressure [10 − 24 ≤ p(O 2 )/bar ≤ 1, T = 700°C] by application of impedance spectroscopy. The yttria and ceria contents of

Inorganic Materials, 2014

We report a study and comparative analysis of the medium temperature (850-1000°C) ionic and total conductivities of zirconia stabilized by yttria and scandia based mixed oxides. Zirconia stabilized by combined yttria and scandia based dopants is shown to have low electronic conductivity in a wide range of oxygen activities. Our data suggest the possibility of using the synthesized materials as membranes in inter mediate temperature ceramic fuel cells.