As-Sintered Manganese-Stabilized Zirconia Ceramics with Excellent Electrical Conductivity

Abstract

As promising electrolyte materials in intermediate-temperature solid oxide fuel cells (IT-SOFCs), Sc-stabilized ZrO2 (ScSZ) and Y-stabilized ZrO2 (YSZ) electrolytes continue to be plagued by high cost and low intermediate conductivity. To mitigate these problems, Mn has been chosen as a new stabilization element for the synthesis of Mn-stabilized ZrO2 ceramics (MnSZ) through solid state sintering. Microstructures and electrical properties of micron-crystalline Zr1−xMnxO2−δ (x = 0.15, 0.20 and 0.25) ceramics electrolytes for IT-SOFCs have been systematically evaluated. Within the applied doping content, Mn2+ ions can enter the ZrO2 crystal lattice, leading to the formation of single cubic phase samples. Electrical conductivity measurements in the temperature range between 400 °C and 1000 °C show a sharp increase in conductivity due to Mn doping. The highest conductivity is obtained from the Zr0.75Mn0.25O2−δ samples, being 0.0144 S/cm at 600 °C and 0.182 S/cm at 1000 °C. The electrical conductivity at 600 °C is twice higher than that of the YSZ and two orders of magnitude higher than that of the ScSZ. These properties can fulfill the conductivity requirement (∼1 × 10−2 S/cm) for the electrolyte. Therefore, based on this study, we propose that Mn stabilized ZrO2 is a promising candidate as a solid electrolyte for IT-SOFCs.

The explanation of electrical properties changes under NH3 and H2 containing atmospheres in risen temperatures of ceria- and zirconia-based solid electrolytes by means of electrochemical impedance spectroscopy

“…The Zr 4+ ions are partially substituted by ions of lower valence and the oxygen vacancies are formed to preserve the charge neutrality of the system. The mentioned processes can be described by the formulas written for doping with divalent and trivalent cations descendant from oxide dopant, respectively: 1 2 Doping with tetravalent ions from MnO 2 or SiO 2 is also possible and improves mechanical stability of the materials [21][22][23][24][25].…”

Phase Formation and Stabilization Behavior of Ca-PSZ by Post-Heat Treatment II: CaOx-ZrO2(1 − x) (x = 5–10 mol%)

“…Various studies have been conducted to improve the mechanical and thermal properties of zirconia for high-temperature applications by using compounds, such as Y 2 O 3 , MgO, Al 2 O 3 , Bi 2 O 3 , and CaO, as stabilizers of the zirconia phase [13,14]. Doping of these stabilizers induces stabilization by reducing the c/a lattice constant ratio of zirconia on the tetragonal to form a structure with low residual stress inside the lattice by reducing distortion in the tetragonal phase [15,16].…”

Advances in Electrical Discharge Machining of Insulating Ceramics

“…The graphs for other types of dielectric and semiconductive oxide and nitride ceramics have similar trends and vary in σ 0 . For crystalline ceramics, the observed increase in specific and volumetric electrical conductivity is less pronounced, and for metals, it has the opposite tendency [24,39]. An introduction of 30-40 vol.…”