Novel S,N co-doped Ba2In2-xCrxO5+y oxides: Synthesis and optical properties

The (S, N) co-doped Ba₂In_2-xCr_xO_5+y (0 ≤ x ≤ 0.5) oxides are successfully obtained by mixing the Ba₂In_2-xCr_xO_5+y oxides and thiourea through a simple ball milling method followed by sintering at 400 °C for 3 h. The colors of the compounds change from orange-brown to yellow-green after reacting with thiourea. When Cr amount is small (x = 0.1), the crystal structure of (S, N) co-doped Ba₂In_2-xCr_xO_5+y is orthorhombic Ba₂In₂O₅ phase. When x ≥ 0.3, the crystal structure of the sample is cubic BaInO_2.5 phase. And this phase transition is the same as Ba₂In_2-xCr_xO_5+y. XPS results reveal that Cr⁶⁺ in Ba₂In_2-xCr_xO_5+y (0 ≤ x ≤ 0.5) oxides are reduced to Cr³⁺ after sintering. S exists in both cation and anion forms, and N exists in substitutional forms. UV–Vis analysis indicates that the yellow-green hue comes from the d-d transition of Cr³⁺, and the doping of S, N ions leads to a red shift of the absorption edge of the samples.     

Mesoporous Fe-doped In2O3 nanorods derived from metal organic frameworks for enhanced nitrogen dioxide detection at low temperature

Mesoporous Fe-doped In₂O₃ nanorods derived from metal-organic frameworks (In/Fe-MIL-68s) were synthesized for NO₂ detection. The morphologies, structures and NO₂ gas-sensing performances of the Fe–In₂O₃ nanorods were systematically investigated. Texture characterizations demonstrate that the as-prepared Fe–In₂O₃ nanorods show rich porous structures, high specific surface areas and reduced grain sizes. Gas-sensing measurements display that the Fe–In₂O₃ nanorods derived from In/Fe-MIL-68s with the Fe(Ⅲ) content of 5 mol.% (Fe(5)-In₂O₃) exhibit high response (82) and short response/recovery time (70/65 s) towards 2 ppm NO₂ at 80 °C compared with their counterparts. Besides, superior selectivity and good stability are observed. The sensing mechanism studies reveal that the improved gas-sensing performances are attributed to the decrease in the gran size, the formation of rich oxygen vacancies and band gaps narrowing caused by Fe(Ⅲ) doping. Therefore, this work indicates that the Fe–In₂O₃ nanorods derived from metal-organic frameworks precursors can be a promising candidate for NO₂ detection.     

Photoluminescence Properties of Heavily Eu3+‐Doped BaCa2In6O12 Phosphor for White‐Light‐Emitting Diodes

Heavily Eu³⁺‐doped BaCa₂In₆O₁₂ phosphors were prepared by conventional solid‐state reaction, and its structural properties were investigated by means of Rietveld refinement method using an X‐ray source. XRD patterns confirm the hexagonal phase of BaCa₂In₆O₁₂: Eu³⁺ phosphors. The obtained spectrum data indicate that the emission spectra of Ba_1?xEu_xCa₂In₆O₁₂ samples excited at 393 nm exhibit a series of shaped peaks assigned to the ⁵D_0,1,2,3 →⁷F_J (J = 0,1,2,3,4) transitions. Luminescence from the higher excited states, such as ⁵D₁, ⁵D₂, and ⁵D₃, were also observed even though the Eu³⁺ concentration was up to x = 0.4. More importantly, the Ba_1?xEu_xCa₂In₆O₁₂ phosphor still emits white luminescence, when the Eu³⁺ ion concentration is up to x = 0.07 before concentration quenching is observed, which shows that the phosphor is a promising single‐phase phosphor for near ultraviolet (NUV) light‐emitting diodes (LED). Furthermore, the temperature's impact on white luminescent properties was studied. Finally, a white‐light‐emitting diodes (W‐LEDs) fabricated with the Ba_0.95Eu_0.05Ca₂In₆O₁₂ phosphor incorporated with an encapsulant in ultraviolet LEDs (λ_max = 395 nm) is discussed.     

Ionic/electronic mixed conduction relations in perovskite-type oxides by defect structure

Perovskite-type oxides La_1-aA_aM_1-bB_bO_3-x with A=Sr²⁺, Ln³⁺, Ce⁴⁺ and M=Fe, Co, Ga; B=Co, Fe, Mg were prepared in the concentration range a=0·1 to 1 mol and b=0·1 to 0·5 mol. Additionally, A-substoichiometric compositions were prepared. Preparation conditions for monophase materials and structure types of the perovskite were determined by X-ray investigation. The electrical conductivity as a function of pO₂ in the range 10⁵>pO₂>10⁻¹⁴ Pa and temperature (500 to 1000°C) was measured on ceramic shapes by a dc four-point technique in combination with solid electrolyte coulometry. The ionic part of conductivity in mixed conductors was determined by oxygen permeation measurements. The II–III-perovskites Sr(Co,Fe)O_3-x in their stabilized form are excellent mixed conductors (maximum 500 S cm⁻¹ at 400°C) and have up to 2 orders of magnitude higher oxygen ionic conductivity than the preferred III–III-perovskite La(Sr)Mn(Co)O_3-x. The oxygen ionic conductivity of the electrolyte La(Sr)Ga(Mg)O_3-x, was increased by doping with 0·1 mol Co. By applying higher Co or Fe doping concentrations the lanthanum gallate, becomes a mixed conductor.     

Preparation and conductive properties of double perovskite oxides Ba3Ba1+xTa2-xO9-δ

In this work, Ba₃Ba_1+xTa_2-xO_9-δ (x = 0, 0.1, 0.3, and 0.5) double perovskite proton conductors were prepared by solid-state reaction process. Phase compositions and microstructures were characterized by X-ray diffraction and field emission scanning electron microscope techniques. valence and semi-quantitative composition of components were identified by X-ray photoelectron spectroscopy. Conductivities of Ba₃Ba_1+xTa_2-xO_9-δ were then measured under various vapor and oxygen pressures by AC impedance spectroscopy technique. Results revealed linear increase in total conductivities of Ba₃Ba_1+xTa_2-xO_9-δ oxides as a function of temperature. Ba₃Ba_1.3Ta_1.7O_8.55 exhibited the highest total conductivity of 8.41 × 10^?4 S cm^?1 under humidity and 800 °C. The transport numbers calculated by defect equilibria model revealed. Ba₃Ba_1+xTa_2-xO_9-δ oxides as pure proton conductors at 400–800 °C. Also, transport numbers of oxide ions and holes both increased with temperature. Ba₃Ba_1.3Ta_1.7O_8.55 illustrated the highest protonic transport number of 0.60 at 800 °C. In sum, these results suggest that Ba₃Ba_1+xTa_2-xO_9-δ oxides display excellent proton conductivity.     

Hot-corrosion behavior of calcium-magnesium aluminosilicate melts on Ba1/3Sr1/3Ca1/3Al2Si2O8

Hot-corrosion behavior of Ba_1/3Sr_1/3Ca_1/3Al₂Si₂O₈ (BSCAS) in the presence of molten calcium-magnesium-aluminum-silicate (CMAS) is investigated in the temperature range of 1250–1350 °C. In comparison, the hot corrosion behavior of Ba_0.5Sr_0.5Al₂Si₂O₈ (BSAS) is also studied under the same conditions. The results indicate that CMAS corrosion of both BSCAS and BSAS is caused by the interdiffusion of Ba/Sr and Ca between CMAS and corroded samples. The presence of Ca cations in BSCAS lowers the diffusion driving force of Ca cations between CMAS and BSCAS, resulting in a reduced diffusion rate of Ca cations from CMAS into BSCAS. Moreover, the sluggish diffusion effect of multi-component cations hinders the outward diffusion of Ba/Sr cations from BSCAS. Thus, the BSCAS shows a better CMAS corrosion resistance than BSAS.     

Synthesis and Enhanced Electrochemical Performance of Sm‐Doped Sr2Fe1.5Mo0.5O6

Sr₂Fe_1.5Mo_0.5O₆ (SFM) is a mixed ionic and electronic conductor which can be used as both anode and cathode materials in intermediate‐temperature solid oxide fuel cell. By doping Sm into the Sr‐site, the electrical conductivity of SFM is enhanced effectively. The single cell with a configuration of Sr_1.8Sm_0.2Fe_1.5Mo_0.5O₆|La_0.8Sr_0.2Ga_0.83Mg_0.17O_2.815| Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃ obtained maximum power densities of 459, 594, and 742 mW cm⁻² with H₂ as the fuel at 750, 800, and 850 °C, respectively. The results suggest that doping with Sm is a very promising way in enhancing the electrical conductivity of SFM and consequently can greatly improve its anode performance.     

Rational modification of traditional La0.5Sr0.5(Fe/Mn)O3 cathodes for proton-conducting solid oxide fuel cells: Inspiration from nature

By screening a series of La_0.5Sr_0.5MnO_3-δ (LSM)-La_0.5Sr_0.5FeO_3-δ (LSF) solid solutions using first-principles calculations, an optimal solid solution of LSM and LSF was chosen as the cathode for proton-conducting solid oxide fuel cells (H–SOFCs). In terms of oxygen vacancy formation energy, O₂ adsorption energy, bond length of adsorbed O₂, and O p-band center, La_0.5Sr_0.5Mn_0.875Fe_0.125O₃ (LSMF125) and La_0.5Sr_0.5Mn₂₅Fe_0.75O₃ (LSMF75) exhibited superior properties. Subsequent experimental investigations revealed that the H–SOFC with the LSMF75 cathode performed better than the cell with the LSMF125 cathode. The structure analysis revealed that LSMF75 has both Mn and Fe cations on its surface, similar to the designs of several naturally occurring enzymes, hence the increased cathode activity. By improving the LSMF75 cathode further, the cell utilizing the LSMF75 cathode attained a peak power density of 1238 mW cm^-2 at 700 °C, which was much greater than that of the cells using the LSM or LSF cathodes, illustrating the benefits of using the LSM-LSF solid solution. Additionally, the good chemical stability of the LSMF75 cathode was maintained, allowing for 150 h of stable operation under operational conditions.     

Reversible Reaction with CO2 and Control of CO2 Absorption/Desorption Properties of Ba2(Fe1−xInx)2O5 Solid Solutions

Ba₂(Fe_1?xIn_x)₂O₅ was prepared by a solid‐state reaction under a N₂ flow. It was revealed that the solid solutions had a cubic perovskite structure with disordered oxygen vacancies at room temperature. Thermogravimetry and X‐ray diffraction measurements revealed that Ba₂(Fe_1?xIn_x)₂O₅ can reversibly react with CO_2. It was found that the equilibrium temperature of the reaction could be controlled by preparing solid solution.     

Synthesis and Crystal Structure of Na2Ba9Si20O50—An Intermediate Phase Along the Join Na2Si2O5‐BaSi2O5

Single crystals of Na₂Ba₉Si₂₀O₅₀ were obtained from solid state reactions performed along the join Na₂Si₂O₅‐BaSi₂O₅. The crystal structure has been determined from a data set collected at ambient temperatures and subsequently refined to a residual of R(|F|) = 0.0328 for 2211 independent reflections. The compound belongs to the group of phyllosilicates and adopts the monoclinic space group C2/m with the following lattice parameters: a = 39.111(3) Å, b = 7.6566(6) Å, c = 8.2055(6) Å, β = 97.319(6)°, V = 2437.2(3) Å³, Z = 2. Furthermore, weak one‐dimensional diffuse streaks running parallel to a* as well as a very small number of low intensity reflections at b*/3, indicating the presence of a superstructure, were observed. Basic buiding units are silicate layers parallel to (40‐1) which can be obtained from the condensation of single chains with a periodicity of four running along [010]. The sheets can be partitioned into two kinds of consecutive strips containing (i) a sequence of four‐ and eight‐membered rings and (ii) a four‐ring wide “zig‐zag shaped” unit consisting of exclusively six‐membered rings. The sodium and barium cations—distributed among six crystallographically independent positions—are sandwiched between subsequent layers and are linked to seven to nine nearest oxygen neighbors. The structure of Na₂Ba₉Si₂₀O₅₀ is closely related to that of K₂Ba₅Si₁₂O₃₀ and K₂Ba₇Si₁₆O₄₀, respectively. There are strong arguments that the previously claimed phase Na₄Ba₈Si₂₀O₅₀ is actually misinterpreted Na₂Ba₉Si₂₀O₅₀ and that the composition of the intermediate phase along the join Na₂Si₂O₅–BaSi₂O₅ is slightly different from that described in the literature.     

Ba0.95La0.05Fe0.8Ni0.2O3−δ perovskite as efficient cathode electrocatalysts for proton-conducting solid oxide fuel cells

The key issue that limits the electrochemical performance of proton-conducting solid oxide fuel cells (H⁺-SOFCs) is the sluggish kinetics of the oxygen reduction reaction (ORR) of cathode at intermediate and low temperatures. Herein, oxygen vacancy engineering is conducted on cobalt-free Ba_0.95La_0.05FeO_3?δ (BLF) by nickel substitution, which is confirmed by density functional theory computations. Nickel-substituted BLF material (Ba_0.95La_0.05Fe_1?xNi_xO_3?δ (x = 0, 0.1, 0.2, 0.3)) can promote the generation of oxygen vacancies and improve catalytic activity, which is found to be in line with the experimental results of XPS. The phase structure, microstructure, and electrochemical performance of Ba_0.95La_0.05Fe_0.8Ni_0.2O_3?δ (BLFNi0.2) are well-investigated. The single cells with the BLFNi0.2-BaCe_0.7Zr_0.1Y_0.1Yb_0.1O_3?δ (BCZYYb) composite cathode achieve low polarization resistance (R_p) of 0.099 Ω cm² and a peak power density of 631 mW cm^?2 at 700 °C while maintaining good durability for 120 h with no observable degradation. The results demonstrate that Ni-doped BLF is a promising cobalt-free cathode material for H⁺-SOFCs.     

High-entropy oxide phases with magnetoplumbite structure

Sintering of oxides and carbonates at 1400 °C gives crystalline high-entropy single phase products with a BaFe₁₂O₁₉ (magnetoplumbite) structure containing 5 doping elements at high concentration level: Ba(Fe₆Ti_1·2Co_1·2In_1.2Ga_1.2Cr_1.2)O₁₉. The complete list of explored substitutions includes K, Ca, Sr, Pb, La, Bi, Al, Ga, In, Ti, V, Cr, Mn, Co, and Ni. Loading to the batch more than 5 dopants or introduction of NiO, or V₂O₅ initiates formation of second phases like spinels or vanadates. Bi₂O₃ and K₂O are too volatile at sintering temperature and were evaporated from the samples.Due to large ionic radius, the In³⁺ cation is likely to be incorporated not only on Fe³⁺ sites, but also on Ba²⁺ sites, that follow from resulting crystal composition. The smallest di-valent and tri-valent cations, Sr²⁺ and Al³⁺, are found to preferably concentrate together in the same magnetoplumbite phase crystals within one sample.According to elemental analysis of selected hexagonal crystals in the investigated 8 doped samples the most prospective compositions for obtaining high-entropy single phase with magnetoplumbite structure can be formulated as (Ca,Sr,Ba,Pb,La)Fe_x(Al,Ga,In,Ti,Cr,Mn,Co)_12-xO₁₉ where x = 1.5–6.     

Polarization origin and iron positions in indium doped barium hexaferrites

M-type hexaferrite BaFe_12?xIn_xO₁₉ (x = 0.1, 1.2) samples were investigated by high resolution neutron powder diffraction and vibration sample magnetometry in a wide temperature range of 4–730 K. Structural and magnetic parameters were determined including the unit cell parameters, ionic coordinates, thermal isotropic factors, occupation positions, bond lengths and bond angles, microstrain values and magnetic moments. In³⁺ cations may be located only in the Fe1 - 2a and Fe2 - 2b crystallographic positions with equal probability for the x = 0.1 sample. At x = 1.2 about half of In³⁺ cations occupy the Fe5 - 12k positions whilst the other half are equiprobably located in the Fe1 – 2a and Fe2 – 2b positions. The spontaneous polarization was observed for these compositions at 300 K. The influence of structural parameters on the temperature behavior of Fe³⁺(i) - O^2- - Fe³⁺(j) (i, j = 1, 2, 3, 4, 5) indirect superexchange interactions was established. With the substitution level increase the superexchange interactions between the magnetic positions inside and outside the sublattices are broken which leads to a decrease in the value of the corresponding magnetic moments.     

Electrochemical Performance of Cobalt‐free Nd0.5Ba0.5Fe1–xNixO3–δ Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells

A new series of cobalt‐free perovskite‐type oxides, Nd_0.5Ba_0.5Fe_1–xNi_xO_3–δ (0 ≤ x ≤ 0.15), have been prepared by a citric acid‐nitrate process and investigated as cathode materials for proton conducting intermediate temperature solid oxide fuel cells (IT‐SOFCs). The conductivity of the oxides was measured at 300–800 °C in air. It is discovered that partial substitution of Ni for Fe‐sites in Nd_0.5Ba_0.5Fe_1–xNi_xO_3–δ obviously enhances the conductivity of the oxides. Among the series of oxides, the Nd_0.5Ba_0.5Fe_0.9Ni_0.1O_3–δ (NBFNi10) exhibits the highest conductivity of 140 S cm⁻¹ in air at 550 °C. A single H₂/air fuel cell with proton‐conducting BaZr_0.1Ce_0.7Y_0.2O_3–δ (BZCY) electrolyte membrane (ca. 40 μm thickness) and NBFNi10‐BZCY composite cathode and NiO‐BZCY composite anode was fabricated and tested at 600–700 °C. The peak power density and the interfacial polarization resistance (R_p) of the cell are 490 mW cm⁻² and 0.15 Ω cm² at 700 °C, respectively. The experimental results indicate that NBFNi10 is a promising cathode material for the proton‐conducting IT‐SOFCs.     

Effect of Fe Doping on Layered GdBa0.5Sr0.5Co2O5+δ Perovskite Cathodes for Intermediate Temperature Solid Oxide Fuel Cells

Layered perovskite cathode materials have received considerable attention for intermediate temperature solid oxide fuel cells (IT‐SOFCs) because of their fast oxygen ion diffusion through pore channels and high catalytic activity toward the oxygen reduction reaction (ORR) at low temperatures. In this study, we have investigated the effects of Fe substitution for the Co site on electrical and electrochemical properties of a layered perovskite, GdBa_0.5Sr_0.5Co_2?xFe_xO_5+δ (x = 0, 0.5, and 1.0), as a cathode material for IT‐SOFCs. Furthermore, electrochemical properties of GdBa_0.5Sr_0.5CoFeO_5+δ–yGDC (y = 0, 20, 40, and 50 wt%) cathodes were evaluated to determine the optimized cell performance. At a given temperature, the electrical conductivity and the area‐specific resistances (ASRs) of GdBa_0.5Sr_0.5Co_2?x Fe_xO_5+δ decrease with Fe content. The lowest ASR of 0.067 Ω·cm² was obtained at 873 K for the GdBa_0.5Sr_0.5CoFeO_5+δ. The GdBa_0.5Sr_0.5CoFeO_5 + δ composite with 40 wt% GDC was identified as an optimum cathode material, showing the highest maximum power density (1.31 W/cm²) at 873 K, and other samples also showed high power density over 1.00 W/cm².     

Effects of non-stoichiometric defects on the dielectric properties of (Ba0.5Sr0.5)xTiO3-ZnGa2O4 composite ceramics

In order to explore the effects of non-stoichiometric defects on the dielectric properties of composite ceramics, 70 wt% (Ba_0.5Sr_0.5)_xTiO₃-30 wt%ZnGa₂O₄ ((BS)_xT50-ZG, x = (Ba + Sr)/Ti = 0.99, 1.00, 1.01 and 1.05) composite ceramics were fabricated by the traditional sintering technique. The association between structure and dielectric properties has been studied. The results show that the distortion of the crystal lattice brought by the partial Schottky defects, namely [V″_Ba,Sr–V^˙˙_O]^× and [V′′′′_Ti–2V^˙˙_O]^×, induces a decrease in the Curie temperature of (BS)_xT50-ZG composite ceramics. The orientation of the elastic dipoles brought by oxygen vacancies causes the pinning of the domain walls, which reduces the dielectric loss at low frequencies. Tunability is related to the dipole polarization caused by [V″_Ba,Sr–V^˙˙_O]^× and [V′′′′_Ti–2V^˙˙_O]^× defect complexes. In addition, compared with the composite ceramic with x = 1, the Q values of the composite ceramics with x < 1 and x > 1 decreases due to the deterioration of the microstructure homogeneity and the enhancement of the disorder of the B-site cations in (BS)_xT50.     

Effect of Sr and Ca substitution of Ba on the photoluminescence properties of the Eu2+ activated Ba2MgSi2O7 phosphor

The effects of Sr and Ca substitution of Ba on the Ba_1.98-xSr_x(Ca_x)MgSi₂O₇:Eu²⁺ photoluminescence properties have been investigated. The physical mechanisms for the photoluminescence variations are discussed. With Rietveld refinement method, the crystal structure of Ba_1.98MgSi₂O₇:0.02Eu²⁺ and the lattice parameters of Sr and Ca substituted phosphors were refined. The emission band shift, the photoluminescence intensity variation, the phosphor chromaticity evolution, the Eu²⁺ lifetime distribution and the thermal stability elevation were investigated. With Sr and Ca substitution, the cell is shrinks. The cell shrinkage is resulting in the increase of the Eu²⁺ 5d electron crystal field splitting intensity, which is the reason for the emission band shift towards the long wavelength band. The photoluminescence intensity is increased firstly and then decreased. The intensity variation is the competitive result between the increase of the crystal structure rigidity and the rise of the lattice defect. The correlated color temperature can be cut down and the color purity can be adjusted. The photoluminescence life time of Eu²⁺ is raised firstly and then decreased. For Sr and Ca substitution, the thermal stability can be elevated. With the forbidden band gap calculation, the reason for the thermal stability elevation was investigated that for the substituted phosphors the forbidden band gap is enlarged and then limits the Eu²⁺ 5d self-ionization from the splitting levels to the conduction band. This work reveals that the Sr and Ca substitution of Ba can elevate the Ba_1.98-xSr_x(Ca_x)MgSi₂O₇:Eu²⁺ photoluminescence properties and improve the applications for the White Light Emitting Diode.     

Tuning ORR electrocatalytic functionalities in CGFO-GDC composite cathode for low-temperature solid oxide fuel cells

Mixed ionic and electronic conduction (MIEC) in the composite cathode can alter oxygen stoichiometry and other physiochemical properties, eventually promoting the electrocatalytic functionalities for oxygen reduction reaction (ORR) at low operational temperatures (<650 °C). Here, we demonstrate a composite cathode of CoGd_0.8Fe_1.80O₄ /Gd_0.10Ce_0.9O_2?δ (CGFO-GDC), which delivers low electrode polarization resistance of 0.60 Ω cm² at 550 °C. The best-performing sample CGFO-GDC exhbits the peak power density (PPD) of 611-343 mW cm^?2 at 550-470 °C under a fuel cell conditions. Moreover, durability measurement verifies CGFO-GDC as a chemically stable cathode with improved ORR catalytic functionality. Additionally, first principle calculations using density function theory (DFT) were also conducted to analyze the ion diffusion mechanism of fabricated CGFO-GDC cathode. Our findings certify that introducing ionic conducting GDC into CGFO sample improves the catalytic functionalities. As a result, the composite CGFO-GDC based SOFC delivers minimum electrode polarization resistance with improved power output owing to its enhanced oxygen vacancies and fast catalytic reactions at 550 °C.     

High temperature failure modes of In2O3 thin films and improved thermal stability using Al2O3/ZrO2 protective layers

The limiting temperature of an In₂O₃ thin film sensor is much lower than its melting point. Herein, the failure modes of In₂O₃ thin films at high temperatures, including sublimation and changes in composition, have been studied. The edge and surface layer sublimation rates increased dramatically at 1350 °C, indicating that it is the limiting temperature of no-protection In₂O₃ films. In addition, oxygen atoms will escape from In₂O₃ thin films at high temperatures, forming oxygen vacancies. As the main current carrier type in In₂O₃, the increasing number of oxygen vacancies affects the resistance of In₂O₃ thin film sensors. To solve these problems and promote the high temperature performance of In₂O₃ thin films, protection methods based on Al₂O₃ and ZrO₂ layers have been investigated. The ZrO₂ protective layer alleviated the serious considerable sublimation of In₂O₃ thin films at high temperatures, and the Al₂O₃ protective layer was beneficial for reduction the escape of oxygen atoms. Finally, different protection layers were evaluated by in-situ resistivity measurements of In₂O₃ thin films at high temperatures. The resistance of the In₂O₃ thin film resistor with a protective multilayer consisting of Al₂O₃ and ZrO₂ remained stable at 1360 °C, verifying the protection method effectively increased the thermal stability of In₂O₃ thin films.