Stabilized Zirconia Substrates Research Articles

LaFeO3 thin films on Yttria Stabilized Zirconia flexible substrate

Thin films of LaFeO3 for photocatalytic applications were grown by Pulsed Laser Deposition on a flexible polycrystalline Tetragonal Yttria Stabilized Zirconia substrate (T-YSZ). Their structure and morphology were investigated using scanning electron microscopy, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy (STEM), energy dispersive spectroscopy available in the STEM system, X-ray diffraction, and Raman spectroscopy techniques. The band gap energies and the life time of the charge carrier were deduced from UV-Vis and time resolved fluorescence spectroscopies. The polycrystalline substrate T-YSZ was homogeneously covered by the LaFeO3 films, even at the substrate grain boundaries. The surface of the films presents a nanostructuration with flat ended and tip ended grains. The exposed facets are mainly {100}C. Atomic–scale microstructure investigations revealed twins in LaFeO3 grains, as consequence of the curvature of the T-YSZ substrate. Chemical analyses showed iron and oxygen deficiency in the LaFeO3 layers. Two optical transitions with energies of 1.9 eV and 2.5 eV corresponding to visible light absorption were evidenced, and the average life time of charges carriers was found to be 5 ns.

Mixed Potential Electrochemical Sensors – Ceramic Substrate and Electrolyte Effects on Sensor Response to Methane and Simulated Natural Gas

The US Environmental Protection Agency estimates emissions from US natural gas drilling and processing amounted to 197 million metric tons of CO2 equivalent in 2019.1 Research by Marchese et al. suggests that CH4 emissions could be up to three times higher.2 Current natural gas emissions detection methods consist mainly of active optical monitoring, typically with long path IR sensors.3 These monitoring methods capable of ppb level accuracy are expensive, fragile, and require accurately calibrated mirrors. Mixed potential electrochemical sensors (MPES) are robust, low-cost, and selective sensors, making them appropriate option for methane emission monitoring.4 Previously we have reported on a four electrode MPES with 3 mol% YSZ electrolyte fabricated with direct write 3D printing5, here we investigate substrate and electrode material effects on the sensor response.The response of a four electrode La0.87Sr0.13CrO3, Indium Tin Oxide (In2O3 90 wt%, SnO2 10 wt%), Au, Pt mixed potential electrochemical sensor to methane and simulated natural gas at operating temperatures of 450 – 600 °C was studied. Sensors were fabricated on substrates of yttria stabilized zirconia, ceria stabilized zirconia, and magnesia stabilized zirconia manufactured by direct write extrusion 3D printing of aqueous pastes. These materials are selected to maximize the mixed potential difference by better isolation of the sensing electrodes. Data is presented with a solid electrolyte of 3 mol % yttria stabilized zirconia, and various other solid ceramic electrolytes will be studied. The effect of sensor response with respect to the ionic conductivity of substrate material is studied. The sensor limit of detection for CH4, natural gas, CH4/NH3, and CH4/H2 mixes will be reported. We will also train artificial neural networks to quantify the concentration of CH4 and other subcomponents given a subset of signals taken from the sensors operated at different temperatures.AcknowledgementsThis project was supported by US Department of Energy Office of Fossil Energy and Carbon Management through award DE-FE0031864.References(1) US EPA, O. Estimates of Methane Emissions by Segment in the United States https://www.epa.gov/natural-gas-star-program/estimates-methane-emissions-segment-united-states (accessed 2021 -12 -13).(2) Marchese, A. J.; Vaughn, T. L.; Zimmerle, D. J.; Martinez, D. M.; Williams, L. L.; Robinson, A. L.; Mitchell, A. L.; Subramanian, R.; Tkacik, D. S.; Roscioli, J. R.; Herndon, S. C. Methane Emissions from United States Natural Gas Gathering and Processing. Environ. Sci. Technol. 2015, 49 (17), 10718–10727. https://doi.org/10.1021/acs.est.5b02275.(3) Aldhafeeri, T.; Tran, M.-K.; Vrolyk, R.; Pope, M.; Fowler, M. A Review of Methane Gas Detection Sensors: Recent Developments and Future Perspectives. Inventions 2020, 5 (3), 28. https://doi.org/10.3390/inventions5030028.(4) Garzon, F. H.; Mukundan, R.; Brosha, E. L. Solid-State Mixed Potential Gas Sensors: Theory, Experiments and Challenges. Solid State Ion. 2000, 136, 633–638.(5) Halley, S.; Tsui, L.; Garzon, F. Combined Mixed Potential Electrochemical Sensors and Artificial Neural Networks for the Quantificationand Identification of Methane in Natural Gas Emissions Monitoring. J. Electrochem. Soc. 2021, 168 (9), 097506. https://doi.org/10.1149/1945-7111/ac2465. Figure 1. Four electrode MPES response at 600 °C to CH4 in simulated air, low ethane simulated natural gas in air, and high ethane simulated natural gas in air, from left to right, respectively. Top row – ceria stabilized zirconia substrate. Bottom row – magnesia stabilized zirconia substrate. Figure 1

Fabrication of Fluorite and Perovskite Functional Films by Solution Spray Pyrolysis

Solution Spray Pyrolysis (SST) was successfully implemented to fabricate thin perovskite and fluorite films on dense Yttria Stabilized Zirconia (YSZ) and Lanthanum Strontium Ferrate (LSF70) substrates. These composite structures are ubiquitous in solid oxide fuel cells and electrolyzers, CO gas sensors and ceramic membranes. With this technique, successful in situ manipulation of the film’s functional characteristics such as porosity and thickness is easily achieved by adjusting its functional parameters.In the present contribution, we report on the optimization of the physicochemical parameters of this open atmosphere technique with respect to the substrate temperature and deposition time for the fabrication of films of suitable morphology. Sintered films were characterized by XRD and SEM while thermal analysis was performed on the precursor salts. In addition, AC Impedance analysis was performed on some CGO films in order to assess their electron blocking capability in contact with the LSF substrates.

Thin-film chemical expansion of ceria based solid solutions: laser vibrometry study

Abstract The chemical expansion of Pr0.1Ce0.9O2–δ (PCO) and CeO2–δ thin films is investigated in the temperature range between 600 °C and 800 °C by laser Doppler vibrometry (LDV). It enables non-contact determination of nanometer scale changes in film thickness at high temperatures. The present study is the first systematic and detailed investigation of chemical expansion of doped and undoped ceria thin films at temperatures above 650 °C. The thin films were deposited on yttria stabilized zirconia substrates (YSZ), operated as an electrochemical oxygen pump, to periodically adjust the oxygen activity in the films, leading to reversible expansion and contraction of the film. This further leads to stresses in the underlying YSZ substrates, accompanied by bending of the overall devices. Film thickness changes and sample bending are found to reach up to 10 and several hundred nanometers, respectively, at excitation frequencies from 0.1 to 10 Hz and applied voltages from 0–0.75 V for PCO and 0–1 V for ceria. At low frequencies, equilibrium conditions are approached. As a consequence maximum thin-film expansion of PCO is expected due to full reduction of the Pr ions. The lower detection limit for displacements is found to be in the subnanometer range. At 800 °C and an excitation frequency of 1 Hz, the LDV shows a remarkable resolution of 0.3 nm which allows, for example, the characterization of materials with small levels of expansion, such as undoped ceria at high oxygen partial pressure. As the correlation between film expansion and sample bending is obtained through this study, a dimensional change of a free body consisting of the same material can be calculated using the high resolution characteristics of this system. A minimum detectable dimensional change of 5 pm is estimated even under challenging high-temperature conditions at 800 °C opening up opportunities to investigate electro-chemo-mechanical phenomena heretofore impossible to investigate. The expansion data are correlated with previous results on the oxygen nonstoichiometry of PCO thin films, and a defect model for bulk ceria solid solutions is adopted to calculate the cation and anion radii changes in the constrained films during chemical expansion. The constrained films exhibit anisotropic volume expansion with displacements perpendicular to the substrate plane nearly double that of bulk samples. The PCO films used here generate high total displacements of several 100 nm’s with high reproducibility. Consequently, PCO films are identified to be a potential core component of high-temperature actuators. They benefit not only from high displacements at temperatures where most piezoelectric materials no longer operate while exhibiting, low voltage operation and low energy consumption.

Millimeter-Wave Response of All Metal-Organic Deposited YBCO Transition Edge Bolometer

We report on the response of a monolithic high $\mathrm{T_{c}}$ transition-edge bolometer to about 3 mmWave for the first time. The detector structure consisting of 400-nm $\mathrm{YBa_{2}Cu_{3}O_{7-x}}$ (YBCO) film on buffered yttria stabilized zirconia substrate without any coupled antenna, shows bolometric type responsivity to the 3-mmWave radiation at its transition temperature. The YBCO thin film and $\mathrm{Ce_{0.9}La_{0.1}O_{2}}$ buffer layer are both fabricated by the metal-organic deposition method. The meander line pattern of the bolometer is designed for obtaining maximum absorption and responsivity possible when the polarized radiation of the source is aligned with the pattern. Meander lines are 50 micrometers wide and 1.5-mm long. We have measured amplitude and phase of the response versus modulation frequency of the detector to the linearly polarized 95-GHz source, and the detector was biased at five distinct temperatures at the transition corresponding to five different electrical conductivities of the YBCO film. When the meander lines of the device are parallel to the incident beam polarization, the YBCO pattern is speculated to act as a dissipative antenna resulting in higher absorption leading to high magnitude of the response as observed. The results from the measured phase of the response versus modulation frequency are also in agreement with the discussed absorbed mechanism. The absorption of the YBCO pattern is also measured to depend on the electrical conductivity of the YBCO film and our results show that there is an optimum electrical conductivity for having maximum absorption for this detector. Simulation results for this structure confirm the experiments showing that at electrical conductivity value of $\mathrm{1.33\times 10^{5}}$ S/m we have the maximum absorption for our device. These observations promise design of versatile THz and millimeter-wave detectors with potential for applications in medical and security imaging.

Epitaxial indium tin oxide films deposited on yttrium stabilized zirconia substrate by DC magnetron sputtering

Epitaxial indium tin oxide (ITO) films were successfully prepared on Yttrium Stabilized Zirconia (YSZ) substrates by direct current magnetron sputtering. The epitaxial relationships between ITO films and YSZ substrates were confirmed as ITO (100) || YSZ (001) by XRD θ-2θ scans and phi-scans. The influence of deposition conditions including of substrate temperature, film thickness and sputtering power were studied systematically. The preparation conditions of ITO films were optimized according to flatness and electrical performance. Moreover, the electrical properties were compared between ITO films deposited on YSZ (100) substrates and quartz substrates, and the former samples have better conductivities.

Morphology and Photoluminescence Properties of Lu2O3:Eu Films Prepared by LCVD Method

Efficient and dense scintillator Lu2O3:Eu is one of the most promising candidates used for high resolution hard X-ray imaging detector. In this paper, Lu2O3:Eu films were prepared through laser chemical vapor deposition on single crystal yttrium stabilized zirconia substrates. The structure and morphology of the films were investigated by X-ray diffraction and scanning electron microscopy. Lu2O3:Eu films, with micro-columnar and single crystal morphologies, were obtained through adjusting growth parameters. The growth mechanisms were also discussed based on related phenomena. The photoluminescence properties of the films were measured and discussed, including photoluminescence excitation, photoluminescence spectra and photoluminescence decay curves.

Chromium Trihalides CrX3 (X = Cl, Br, I): Direct Deposition of Micro‐ and Nanosheets on Substrates by Chemical Vapor Transport

AbstractThe experimental observation of intrinsic ferromagnetism in single layered chromium trihalides CrX3 (X = Cl, Br, I) has gained outstanding attention recently due to their possible implementation in spintronic devices. However, the reproducible preparation of highly crystalline chromium(III) halide nanolayers without stacking faults is still an experimental challenge. As chromium trihalides consist of adjacent layers with weak interlayer coupling, the preparation of ultrathin CrX3 nanosheets directly on substrates via vapor transport proves as an advantageous synthesis technique. It is demonstrated that vapor growth of ultrathin highly crystalline CrX3 micro‐ and nanosheets succeeds directly on yttrium stabilized zirconia substrates in a one‐step process via chemical vapor transport (CVT) in temperature gradients of 100 K (600 °C → 500 °C for CrCl3 and 650 °C → 550 °C for CrBr3 or CrI3) without a need for subsequent delamination. Due to simulation results, optimization of synthesis conditions is realized and phase pure CrX3 nanosheets with thicknesses ≤25 nm are obtained via short term CVT. The nanosheets morphology, crystallinity, and phase purity are analyzed by several techniques, including microscopy, diffraction, and spectroscopy. Furthermore, a potential subsequent delamination technique is demonstrated to give fast access to CrX3 monolayers using the example of CrCl3.

Formation of the orthorhombic phase in CeO2-HfO2 solid solution epitaxial thin films and their ferroelectric properties

The formation of the metastable orthorhombic phase (Pca21) in CeO2-HfO2 solid solution epitaxial thin films has been demonstrated. The films were deposited at room temperature on (001)yttria stabilized zirconia substrates by an Ar ion-beam sputtering method and subsequent annealing, where the Ce content of the films was controlled by changing the composition, x = [CeO2]/([HfO2]+[CeO2]), of the sputtering target. The chemical states of cations in xCeO2 − (1 − x)HfO2 (x = 0–0.5) thin films have been investigated by X-ray photoelectron spectroscopy, which confirmed the coexistence of Ce4+ and Ce3+. The crystal structure has been investigated by using X-ray diffraction and transmission electron microscopy. These analyses revealed that the metastable orthorhombic phase was formed in the films with x = 0.03–0.1, and the lattice constants of that phase increased with the Ce content. Microstructural analysis has been performed by using scanning transmission electron microscopy, which revealed a multidomain structure consisting of the orthorhombic phase. The polarization-electric field loop for the film with x = 0.1 indicated ferroelectricity, demonstrating that CeO2-HfO2 solid solution thin films are candidates for fluorite-type ferroelectrics.

Effects of Co-doping on Densification of Gd-doped CeO2 Ceramics and Adhesion Characteristics on a Yttrium Stabilized Zirconia Substrate

Effects of Co-doping on Densification of Gd-doped CeO2 Ceramics and Adhesion Characteristics on a Yttrium Stabilized Zirconia Substrate

Microstructural Effects on Disorder and Transport in Irradiated Pyrochlore Thin Films

Complex oxides exhibiting fast ion conduction have surfaced as attractive materials for various applications such as fuel cells, electrolyzers, sensors and gas separation membranes. Literature shows that many of the studies of these materials place emphasis on improving ionic conductivity. Here we focus on improving our understanding of how defects within the microstructure impact ionic transport. We employ irradiation as a tool to induce disorder in oxide materials, then utilize a number of different characterization techniques to determine the relationship between disorder and oxygen ion conduction. In this study, Gd2Ti2O7 (GTO) pyrochlore thin films are prepared on single and polycrystalline Yttria Stabilized Zirconia (YSZ) substrates using RF Magnetron sputtering. Electrochemical Impedance Spectroscopy measurements are performed as a function of temperature in the through-plane configuration using a Cascade Microtech Microprobe Test Station equipped with a Linkam high temperature stage. The EIS data is used to determine the conductivity of GTO films with varying degrees of irradiation induced structural disorder. This work examines how the underlying microstructure in polycrystalline and highly oriented thin films (grown on polycrystalline and single crystal YSZ substrates, respectively) influences irradiation induced disordering and transport properties. Acknowledgements This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

Electrolyte supported solid oxide fuel cells with the super large size and thin ytterbia stabilized zirconia substrate

In this work, the (ZrO2)0.95(Yb2O3)0.05(5YbSZ) electrolyte supported SOFCs with the large area of 10 cm × 10 cm and thin substrate of about 70 μm are prepared, and the microstructures, electrochemical and anti-redox properties of the single cells are investigated systematically. The powders of 5YbSZ with the tetragonal and cubic mixed phase are synthesized by the so-called “solid–liquid composite method” at a somewhat low temperature of 1100 °C. The 5YbSZ electrolyte substrates which are prepared by the tape-casting, multilayer-lamination and sintering method showed the optimal comprehensive performances with the sintering temperature being 1500 °C. By using these electrolyte substrates, the NiO+GDC/5YbSZ/LSM+5YbSZ single cells are obtained at the co-sinter temperature of 1100 °C. The power densities of these cells can reach 0.56 W cm−2 at the output voltage of 0.7 V, and the degradation rate can attain 1.45% kh−1 under a constant current density of 0.2 A cm−2 at the temperature of 830 °C. After 11 redox cycles, no crack through the 5YbSZ electrolyte can be found in the single cells, and the electrochemical properties of the 5YbSZ electrolyte supported single cells show an acceptable degradation.

Nanostructured Zn and ZnO nanowire thin films for mechanical and self-cleaning applications

Nanostructured Zn metal films were deposited by thermal evaporation, on borosilicate glass, Quartz, sapphire, lanthanum aluminate and yttria stabilized zirconia substrates. The as-deposited films are nanocrystalline and show a morphology that consists of triangular nanosheets. The films are hydrophobic with contact angles between 102° and 120° with hardness and Young's modulus between 0.15–0.8GPa and 18–300GPa, respectively. Thermal annealing of the films at 500°C results only in partial oxidation of Zn to ZnO, which indicates good oxidation resistance. Annealing also causes transformation of the Zn nanosheets into ZnO nanowires that are polycrystalline in nature. The ZnO nanowires are superhydrophobic with contact angles between 159° and 162°, contact angle hysteresis between 5° and 10° and exhibit a reversible superhydrophobic–hydrophilic transition under UV irradiation. The nanowires are much softer than the as-deposited Zn metal films, with hardness between 0.02 and 0.4GPa and Young's modulus between 3 and 35GPa. The current study thus demonstrates a simple process for fabrication of nanostructured Zn metal films followed by a one-step transformation to nanowires with properties that will be very attractive for mechanical and self-cleaning applications.

(Invited) Impact of Size Scale on Electro-Chemo-Mechanical Coupling Properties in MIECs: Bulk and Thin Film (Pr,Ce)O2-δ

Many oxides exhibit advantageous properties in energy conversion and storage applications, such as solid oxide fuel cells (SOFCs), heterogeneous catalysis, photoelectrochemical cells, and batteries, due in part to their high temperature stability, corrosion resistance, and dopant cation solubility, respectively. In particular, mixed ionic and electronic conducting oxides have been demonstrated to aid in increasing reaction kinetics at electrodes in SOFCs due to the simultaneous presence of electrons and oxygen vacancies. With changes in oxygen partial pressure and temperature during normal operation operation, the defect concentration and hence transport characteristics of MIEC oxides inevitably change. In addition, defects are often coupled to a significant lattice dilation, known as chemical expansion, which under some circumstances leads to mechanical failure. Furthermore, as length scales are reduced, the energetics for electron and vacancy formation have been shown to be modified. In this presentation, recent work examining the the interplay of electro-chemo-mechanical properties of bulk ceramic to thin film size scales will be discussed. This work was facilitated by using the model material system, (Pr,Ce)O2-δ (PCO), which, due to the ease of reduction of Pr from 4+ to 3+ valence, exhibits significant MIEC behavior at relatively high oxygen pressures (e.g. air). Impedance spectroscopy was used to study both the oxygen exchange resistance and oxygen content (via chemical capacitance) of cells consisting of PCO thin films deposited on yttria stabilized zirconia substrates. When compared to defect formation energies derived from a detailed thermogravimetric and conductivity model for bulk PCO, films were found to exhibit enhanced reducibility. This phenomenon was further verified using an in situ optical transmission measurement of films, coupled with chemical capacitance, which correlated the amount of absorbing Pr4+ centers to oxygen vacancy concentration. Additionally, oxygen exchange probed by optical transmission relaxation measurements on “bare” films exhibited slower kinetics as compared to corresponding electrochemical measurements. The role of metal electrodes as well as impurities in modifying oxygen exchange rate will be discussed, as well as new means to improve oxygen exchange of the aged “bare” film surface. Lastly, thermo-chemical expansion measurements of bulk and thin film PCO samples will be presented with discussion related to the atomistic role of individual point defects and defect association.

Determination of Non-Stoichiometry in Mixed Conducting Oxide Thin Films of Arbitrary Chemistry

The dependence of oxygen non-stoichiometry on oxygen partial pressure and temperature is critical to many of the applications of non-stoichiometric oxides in electrochemical energy conversion processes. It has been increasingly recognized that electrochemical methods, in particular, AC impedance spectroscopy, can be used to evaluate this non-stoichiometry. The method is particularly useful for determining the properties of thin films, for which conventional thermogravimetric methods are inapplicable. To date, analysis of the ACIS data to extract non-stoichiometry values has relied on application of various simplifying assumptions for the thermodynamic behavior, limiting the approach to oxides with ideal solution behavior. In this work, we determine the oxygen non-stoichiometry of cerium oxide, which displays non-ideal behavior under certain thermodynamic conditions. The chemical capacitance of single crystal, epitaxial thin films of cerium oxide deposited on yttria stabilized zirconia substrates is measured and related to the oxygen non-stoichiometry using thermodynamic principles. This work will demonstrate the validity of the chemical capacitance measurements to reliably extract non-stoichiometry of a generalized oxide system.

Cerium reduction at the interface between ceria and yttria-stabilised zirconia and implications for interfacial oxygen non-stoichiometry

Epitaxial CeO2 films with different thickness were grown on Y2O3 stabilised Zirconia substrates. Reduction of cerium ions at the interface between CeO2 films and yttria stabilised zirconia substrates is demonstrated using aberration-corrected scanning transmission electron microscopy combined with electron energy-loss spectroscopy. It is revealed that most of the Ce ions were reduced from Ce4+ to Ce3+ at the interface region with a decay of several nanometers. Several possibilities of charge compensations are discussed. Irrespective of the details, such local non-stoichiometries are crucial not only for understanding charge transport in such hetero-structures but also for understanding ceria catalytic properties.

Enhancement of carrier-mediated ferromagnetism in Zr/Fe-codoped In2O3 films

Fe/Zr-codoped In2O3 thin films were grown on yttria stabilized zirconia substrates by pulsed laser deposition. The deposited films exhibited ferromagnetism at room temperature with strong magnetic anisotropy, which was influenced by a magnetostriction effect under tensile stress (i.e., c/a > 1). Both the saturation magnetization and anomalous Hall effect (AHE) were enhanced by increasing charge carrier density via Zr-doping. Our observations, including AHE and magnetic anisotropy, provide strong evidence of intrinsic ferromagnetism at room temperature in these materials.

Growth of rare-earth zirconates-based pyrochlore buffer layers on YSZ for YBCO-coated conductors via chemical solution deposition

Abstract Epitaxial films of rare-earth zirconates, RE2Zr2O7 (RE = La, Nd, Sm and Gd) were grown on yttrium stabilized zirconia (100) single crystal substrates using metal-organic deposition. A precursor solution of 0.25 '0.40 M concentration of total cations was spin-coated on yttrium stabilized zirconia substrates and crystallized at 1 000 8C for 3 h in Ar-4%H2 after calcination at 500 8C for 1 h. X-ray diffraction studies showed that the resulting pyrochlore RE2Zr2O7 films were highly textured with cube-on-cube epitaxy. Atomic force microscopy investigations revealed that the surfaces of La2Zr2O7, Nd2Zr2O7 and Sm2Zr2O7 films had a fairly dense and smooth microstructure without cracks and porosity, but that voids could be seen on the surface of the Gd2Zr2O7 film. Optical microscopy measurements confirmed that the Gd2Zr2O7 precursor solution showed poor wetting behavior on the substrate. It was concluded that the Nd2Zr2O7 and Sm2Zr2O7 films could be potentially used as buffer layers for YBa2Cu3O7-d coated conductors.

Ferroelectricity and Ferrimagnetism of Hexagonal YbFeO3 Thin Films

The coexistence of ferroelectricity and magnetic order in epitaxial hexagonal YbFeO3 (h-YbFeO3) thin films deposited on yttria stabilized zirconia substrates is examined using an impedance analyzer, a second harmonic generation (SHG) microscope, an X-ray diffractometer, a transmission electron microscope and a superconducting quantum interference device magnetometer. The results show that h-YbFeO3 films exhibit ferroelectricity below 350 K with threefold translational periodicity along the [110] direction similar to rare earth manganese oxides, and ferrimagnetism with a four-up and two-down spin configuration of Fe þ3 and Yb þ3 ions along the c-axis at low temperatures. In addition, a possibility of new ferroelectric phases with an electronic origin induced by the magnetic ordering is discussed based upon SHG and D–E hysteresis measurements.

Room temperature ferromagnetism in monoclinic Mn-doped ZrO2 thin films

Theory has predicted that high temperature ferromagnetism (FM) should be found in cubic Mn-doped ZrO2. Our experimental data reveal room temperature FM in Mn-doped ZrO2 thin films grown on LaAlO3 substrates. The largest saturated magnetic moment (Ms) is found to be about 13.8 μB/Mn for the cubic Mn0.05Zr0.95O2 films and it decreases as the Mn content increases. In this case, the intrinsic FM is strongly associated with the cubic structure of Mn-doped ZrO2, and the Mn-Mn exchange interactions via intermediate oxygen atoms is important. Room temperature FM is also observed in monoclinic Mn-doped ZrO2 thin films grown on Yttrium Stabilized Zirconia (YSZ) substrates, however, with a completely different nature. Though pristine monoclinic ZrO2 films are already ferromagnetic, doping Mn can enhance the magnetic moment by about 40% (Ms is 2.68 μB/Mn). Differently from the cubic case, FM in monoclinic Mn-doped ZrO2 films does not come only via exchange interactions, but also from defects.