SrZrO3 Research Articles

Infrared radiation and thermophysical properties of small band gap Cu-doped SrZrO3 perovskite ceramic

High infrared radiation materials have crucial applications in energy saving, heat conversion, and heat dissipation. SrZrO3 (SZO) is a potential material for high infrared radiation, however, its infrared emissivity still needs to be improved. To address this, in this study, Sr(Zr0.9375Cu0.0625)O3-δ (SZCO) perovskite ceramic with high infrared emissivity was prepared, and the impact of Cu ion doping on the electronic structure, infrared radiation characteristics, and thermal conductivity of SrZrO3 were explored. The findings reveal that SZO doped with Cu ions markedly decreases its band gap width from 5.658 eV to 1.467 eV. The infrared emissivity of the SZCO ceramic, sintered at 1200 °C, increases by 28 % in the 3–5 μm band compared to SZO at room temperature. This emissivity positively correlates with temperature, reaching up to 0.95 at 600 °C. The emissivities of SZCO are greater than that of SZO in the 8–14 μm and 1–22 μm band ranges over the test temperature range from room temperature to 600 °C, and both increase with increasing temperature, reaching 0.978 and 0.946 at 600 °C, respectively. Furthermore, the SZCO ceramic demonstrates thermal conductivities ranging from 1.90 to 3.2 W m−1 K−1 below 1400 °C. These results highlight the potential of Sr(Zr0.9375Cu0.0625)O3-δ ceramic as a high infrared radiation material.

Prevention of morphological change for (Ba,Sr)(Co,Fe)O3 cathodes by incorporating (Ce,Gd)O2 for intermediate-temperature solid oxide fuel cells

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) generally exhibits superior cathode activity compared to La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) for intermediate-temperature solid oxide fuel cells (IT-SOFCs). However, the chemical stability of BSCF is inferior to that of LSCF. When BSCF cathodes are sintered at a high temperature of 1050 °C, performance was compromised due to the formation of (Ba,Sr)ZrO3 between the scandia-stabilized zirconia (ScSZ) electrolyte and gadolinia-doped ceria (GDC) interlayer. The oxide ionic conductivity of (Ba,Sr)ZrO3 was low, decreasing the cathode performance. Furthermore, the BSCF grains enlarged, and cobalt oxide formed due to BSCF decomposition, decreasing the active specific surface area. However, by incorporating GDC into the BSCF cathode, the morphology remained unchanged and cobalt oxide formation was prevented, despite (Ba,Sr)ZrO3 still forming. The performance of the cell with the BSCF-GDC composite cathode surpassed that with the BSCF cathode due to decreased polarization resistance attributed to the oxygen surface exchange and diffusion processes in the cathode.

Magneto-Optic and thermoelectric response of doped SrZrO3 for energy storage applications

Using first-principles calculations, we have investigated the electronic, optical, magnetic and thermoelectric properties of the pristine and doped SrZrO3 (SZO) with Mn, Co, and Fe atoms at Sr-site. Our calculations shows that the Mn. Co, and Fe atoms at Sr-site can be easily incorporated in SZO due to their lower formation energies. The pristine SZO exhibit a non-magnetic semiconductor nature with a band gap of 4.06 eV. Interestingly, the dopants Mn, Co, and Fe atoms alters the semiconductor nature of SZO to magnetic one with a band gap values of 1.38(↑)/1.74(↓), 2.98(↑)/0.0(↓), and 0.0(↑)/1.87(↓) for Mn-, Co–, and Fe-doped SZO. This 100 % spin-polarization near the fermi-level, confirming the half-metallic nature of the X-SZO (X = Mn, Co, Fe). Importantly, the magnetic anisotropy energy (MAE) of 1.27 meV, 1.45 meV, and 0.67 meV is estimated for Mn-, Co–, and Fe-doped SZO, respectively. Thus, the realization of MAE could pave a way to utilize Mn-, Co–, and Fe-doped SZO for applications in magnetic semiconductor devices. Optical absorption of Mn-SZO spectra exhibits blueshift upon introducing impurities and materials exhibits good absorption in the visible region. A drop in reflectivity and rise in conductivity in the high energy Ultraviolet region make these materials as potential candidate for fabrication of devices in the field of photodetectors, optoelectronic, power electronics, solar cells, photonic and photovoltaics. The ZT value is recorded 0.35, 0.45, 1.12 and 0.55 for pristine, Mn-SrZrO3, Co-SZO and Fe-SZO respectively at different temperature values. It would be ideal to perform more experimental research on the effective application of these systems in the domains of magnetic semiconductor devices and photo-electronics.

Review of Systematic Tendencies in (001), (011) and (111) Surfaces Using B3PW as Well as B3LYP Computations of BaTiO3, CaTiO3, PbTiO3, SrTiO3, BaZrO3, CaZrO3, PbZrO3 and SrZrO3 Perovskites.

We performed B3PW and B3LYP computations for BaTiO3 (BTO), CaTiO3 (CTO), PbTiO3 (PTO), SrTiO3 (STO), BaZrO3 (BZO), CaZrO3 (CZO), PbZrO3 (PZO) and SrZrO3 (SZO) perovskite neutral (001) along with polar (011) as well as (111) surfaces. For the neutral AO- as well as BO2-terminated (001) surfaces, in most cases, all upper-layer atoms relax inwards, although the second-layer atoms shift outwards. On the (001) BO2-terminated surface, the second-layer metal atoms, as a rule, exhibit larger atomic relaxations than the second-layer O atoms. For most ABO3 perovskites, the (001) surface rumpling s is bigger for the AO- than BO2-terminated surfaces. In contrast, the surface energies, for both (001) terminations, are practically identical. Conversely, different (011) surface terminations exhibit quite different surface energies for the O-terminated, A-terminated and BO-terminated surfaces. Our computed ABO3 perovskite (111) surface energies are always significantly larger than the neutral (001) as well as polar (011) surface energies. Our computed ABO3 perovskite bulk B-O chemical bond covalency increases near their neutral (001) and especially polar (011) surfaces.

Preparation and chemical stability evaluation of Ln2Zr2O7‐SrZrO3 novel composite ceramics cured simultaneously with An and 90Sr

AbstractIn response to the low separation efficiency of actinide nuclide (An) and fission product (FP) in the separation process of high‐level radioactive waste, as well as the large amount of secondary waste. A novel Ln(1‐x)SrxZrO(3.5‐0.5x) (0 ≤ x ≤1) multiphase ceramic waste form (Nd3+ simulating An3+), which can cure both An and Sr simultaneously, was in‐situ synthesized by sol‐gel spray pyrolysis method. The series of multiphase ceramics are composed of cubic pyrochlore phase Nd2Zr2O7 (NZO) and orthorhombic perovskite phase SrZrO3 (SZO), without any accompanying impurities. The two phases exhibit excellent compatibility, and their content can change regularly with the change of x. Nd and Sr occupy their most stable crystal lattice positions, with low transposition doping levels. The density of the composite ceramics is high, and the measured density is as high as 88 % of the theoretical density. The above experimental results confirm that the new multiphase ceramics can cure An and Sr simultaneously and separately, showing strong adaptability to waste components and high chemical stability.

Phase composition and thermophysical properties of Yb–Y Co-doped SrZrO3 coating prepared by suspension plasma spray

In this study, the Yb–Y co-doped SrZrO3 (SZ) coatings [SZYY-1 (Sr1.0(Zr0.9Yb0.05Y0.05)O2.95), SZYY-2 (Sr0.9(Zr0.9Yb0.05Y0.05)O2.85), and SZYY-3 (Sr0.8(Zr0.9Yb0.05Y0.05)O2.75)] were deposited by SPS (Suspension plasma spray) using the corresponding co-precipitation prepared precursors suspension. In the three as-sprayed SZYY coatings, there were some typical suspension plasma-sprayed coating structures, such as columnar crystals, vertical cracks, and micro/nanopores.The TCs (Thermal conductivities) of the three as-sprayed SZYY coatings were 1.23–1.88, 0.80–1.41, and 0.88–1.43 W/(m · K) at 100–1400 °C, respectively, which were at least 19% lower than that of the SZ coating (1.25 W/(m · K), 1000 °C). The TECs (Thermal expansion coefficients) of the three as-sprayed SZYY coatings were (7.8–8.7) × 10−6, (8.0–9.8) × 10−6, and (8.1–9.8) × 10−6/K, respectively (200–1360 °C). The sintering coefficients of the three as-sprayed SZYY coatings were 5.69 × 10−6, 4.29 × 10−6, and 3.84 × 10−6/s, respectively. The SZYY-3 coating showed the best SR (Sintering resistance), followed by the SZYY-2 coating and SZYY-1 coating. The SPS SZYY-2 coating with good phase stability, low TC (Thermal conductivity) and good SR is a promising new TBCs (Thermal barrier coatings) material. It is expected to be an alternative TBCs material for the next generation of high performance gas turbines.

Simulated advanced gas-cooled reactor spent nuclear fuels: Determination of the O/U ratio - an XRD, XPS and Raman study

This paper reports a detailed chemical and materials characterization study of novel Simulated Spent Nuclear Fuels (SIMFuel) which replicate the chemical and microstructural state of Spent Nuclear Fuel (SNF) discharged from a UK Advanced Gas-cooled Reactor (AGR). Recent advances in the analysis of pure UO2 samples by XPS, micro-Raman spectroscopy and XRD, have been assessed for deployment in the characterisation of SIMFuels generally and these AGR SIMFuels in particular. All three analytical methods reveal the extent that the UO2 bulk matrix is defected in the SIMFuels by the presence of lanthanide dopants. XPS, by inspection of the U4f peaks and their satellites, indicates the presence of U(V) in the UO2 matrix as a means to charge compensate for the incorporation of Ln(III) states and presence of a slight hyperstoichiometry in the UO2 solid solution. This was corroborated by detailed Raman analysis of the UO2 matrix of the SIMFuels – wherein the (Ba,Sr)ZrO3 and metallic particle phases, that simulate the precipitated grey phases and ε-particles formed in real spent fuel, were avoided – which indicated the presence of both interstitial oxygens and oxygen vacancies, the latter as a parallel means of charge compensation for the presence of Ln(III). Further confirmation was provided by XRD measurements through observation of a lattice parameter contraction arising from the presence of the smaller U(V) ion in the U(IV)O2 matrix. XPS and Raman allow for the reporting of O/U ratios in the SIMFuels. These XPS and Raman-derived O/U ratios are in good agreement, indicating: (i) that the SIMFuels are near stoichiometric/slightly hyperstoichiometric, concurring with previous analogous studies on real and simulated light water reactor fuels; and (ii) that either technique may find application in the analysis of real fuel analysis, both pre- and post-irradiation.

Synthesis and performance of aluminous cements containing zirconium and strontium as alternatives to the calcium aluminate cements designed for the production of high performance refractories

Composite cements belonging to the CaO–Al2O3–ZrO2 (C-A-Z) and CaO–SrO–Al2O3–ZrO2 (C–Sr-A-Z) systems were evaluated as alternatives to calcium aluminate cements (CACs) for use in the refractory castables technology. The mineralogical phases in the as-synthesized C-A-Z and C–Sr-A-Z clinkers confirmed by XRD and SEM-EDS were CaAl2O4, Ca7ZrAl6O18 and CaZrO3 or (Ca,Sr)Al2O4, (Ca,Sr)Al4O7 and (Ca,Sr)ZrO3, respectively. The present work aimed at developing novel Zr-containing cements with excellent mechanical performance, i.e. modulus of rupture and cold crushing strength. Both hydration behavior of the C-A-Z, C–Sr-A-Z, CAC and their hydration products, were studied with isothermal calorimetry, XRD, SEM-EDS and NMR. Impedance camera instrument was firstly successfully applied for time-resolved electrochemical impedance spectroscopy measurements under nonstationary conditions and record the time-dependent evolution of the Nyquist plots for hydrating cement pastes. A sharp increase in the real part of impedance Z’ versus hydration time were corresponded to the second exothermic peak detected on the calorimetry curves.

Flash Light Sintered Lanthanum Strontium Cobalt Ferrite(LSCF) Electrode for High Performance IT-SOFCs

The high temperature(900oC~) thermal sintering process is necessary to fabricate the Solid oxide fuel cells(SOFCs). However, the chemical reaction has occurred between solid oxide material components, electrode and electrolyte. In the case of lanthanum strontium cobalt ferrite (La0.6Sr0.4Co0.2Fe0.8O3-δ, LSCF) electrode, the SrZrO3(SZO) secondary phase is produced at the electrolyte interface even when using the gadolinium doped ceria(GDC) buffer layer for blocking the strontium and zirconium diffusion. The SZO layer hinders the oxygen ion transfer and deteriorates fuel cell performance. By using a novel flash light sintering(FLS) method, we have successfully solved the problem of secondary phase formation in the conventional high temperature thermal sintering process. The microstructure and thickness of the LSCF electrode are analyzed using a field emission scanning electron microscope(FE-SEM). The strontium diffusion and secondary phase are confirmed by X-ray diffraction (XRD), energy dispersive spectrometer method of SEM, TEM (SEM-, TEM-EDS). The NiO-YSZ anode supported LSCF cathode cells are adopted for electro chemical analysis which is measured at 750oC. The maximum power density of the thermal sintered LSCF cathode at 1050oC is 699.6mW/cm2, while that of the flash light sintered LSCF cathode is 711.6mW/cm2. This result proves that the electrode was successfully sintered without a secondary phase using flash light sintering.

Structural, dielectric and energy storage characteristics of (Pb1−xSrx)(Zr0.80Ti0.20)O3 antiferroelectric compositions

Antiferroelectric(AFE) and Relaxor ferroelectric(FE) ceramics are most popular for energy storage applications. In our work we have selected compositions near the FE-AFE phase boundary in the quaternary phase PbTiO3(PT)-PbZrO3(PZ)-SrTiO3(ST)-SrZrO3(SZ). Bulk ceramics based on the composition (Pb1−xSrx)(Zr0.80Ti0.20)O3 [PSZT] with 0.14 ≤ x ≤ 0.20 were synthesized by mixed oxide method. XRD and Raman studies were carried out to understand the structural modifications as a function of Sr2+ concentration. Structure refinement using Rietveld method revealed a change from rhombohedral(R3c) for x = 0,to a coexistence of rhombohedral(R3c) and tetragonal(P4mm) for x = 0.15,and tetragonal(P4mm) for x > 0.15. Polarization - Electric field measurements revealed a systematic FE to AFE transition on A-site Sr2+- substitution. Weibull distribution analysis for all PSZT ceramics was carried out to obtain the Breakdown dielectric strength (BDS). Recoverable energy density and energy storage efficiency were evaluated from the P-E hysteresis and have been correlated with their microstructure for their potential energy storage applications.

Simultaneous realization of high d and large strain in (K,Na,Li) (Nb,Sb)O3-(Ca,Sr)ZrO3 materials and their application in piezoelectric actuators

A pseudocubic-tetragonal-orthorhombic (PC-T-O) multi-structure was developed in the 0.96(K 0.5 Na 0.47 Li 0.03 ) (Nb 0.92 Sb 0.08 )O 3 -0.04(Ca 0.5 Sr 0.5 )ZrO 3 [(KN 0.47 L 0.03 )NS-CSZ] lead-free piezoceramic. The PC structure observed in this sample was deemed to have an R3m rhombohedral structure. This sample demonstrated a large d 33 (560 pC/N) owing to the existence of the PC-T-O multi-structure. The (KN 0.47 L 0.03 )NS-CSZ thick film also exhibited a large d 33 (560 pC/N) and strain (0.19% at 4.0 kV/mm). The large strain was sustained even after the application of 10 6 electric-field cycles. Therefore, the (KN 0.47 L 0.03 )NS-CSZ thick film exhibited excellent fatigue characteristics and was utilized to fabricate a planar-type actuator, which achieved a large displacement (300 μm) and acceleration (872 G) at 125 V/mm. A cantilever-type multilayer actuator was also prepared using five layers of the (KN 0.47 L 0.03 )NS-CSZ thick film and demonstrated a large displacement (3500 μm) and acceleration (42.96 G) at 250 V/mm. Therefore, the (KN 0.47 L 0.03 )NS-CSZ thick film is a good candidate for fabricating various piezoelectric actuators.

Computational engineering of the oxygen electrode-electrolyte interface in solid oxide fuel cells

The Ce0.8Gd0.2O2−δ (CGO) interlayer is commonly applied in solid oxide fuel cells (SOFCs) to prevent chemical reactions between the (La1−xSrx)(Co1−yFey)O3−δ (LSCF) oxygen electrode and the Y2O3-stabilized ZrO2 (YSZ) electrolyte. However, formation of the YSZ–CGO solid solution with low ionic conductivity and the SrZrO3 (SZO) insulating phase still happens during cell production and long-term operation, causing poor performance and degradation. Unlike many experimental investigations exploring these phenomena, consistent and quantitative computational modeling of the microstructure evolution at the oxygen electrode–electrolyte interface is scarce. We combine thermodynamic, 1D kinetic, and 3D phase-field modeling to computationally reproduce the element redistribution, microstructure evolution, and corresponding ohmic loss of this interface. The influences of different ceramic processing techniques for the CGO interlayer, i.e., screen printing and physical laser deposition (PLD), and of different processing and long-term operating parameters are explored, representing a successful case of quantitative computational engineering of the oxygen electrode–electrolyte interface in SOFCs.

Memristive Behavior of Mixed Oxide Nanocrystal Assemblies

Recent advances in memristive nanocrystal assemblies leverage controllable colloidal chemistry to induce a broad range of defect-mediated electrochemical reactions, switching phenomena, and modulate active parameters. The sample geometry of virtually all resistive switching studies involves thin film layers comprising monomodal diameter nanocrystals. Here we explore the evolution of bipolar and threshold resistive switching across highly ordered, solution-processed nanoribbon assemblies and mixtures comprising BaZrO3 (BZO) and SrZrO3 (SZO) nanocrystals. The effects of nanocrystal size, packing density, and A-site substitution on operating voltage (VSET and VTH) and switching mechanism were studied through a systematic comparison of nanoribbon heterogeneity (i.e., BZO-BZO vs BZO-SZO) and monomodal vs bimodal size distributions (i.e., small-small and small-large). Analysis of the current-voltage response confirms that tip-induced, trap-mediated space-charge-limited current and trap-assisted tunneling processes drive the low- and high-resistance states, respectively. Our results demonstrate that both smaller nanocrystals and heavier alkaline earth substitution decrease the onset voltage and improve stability and state retention of monomodal assemblies and bimodal nanocrystal mixtures, thus providing a base correlation that informs fabrication of solution-processed, memristive nanocrystal assemblies.

Microstructure and Piezoelectricity of (Na,K,Li)(Nb,Sb)O3–(Bi,Na)(Sr)ZrO3–BaZrO3 Ceramics

In this paper, (Na,K)1−xLi.x(Nb,Sb)O3–(Bi,Na)(Sr)ZrO3–BaZrO3 ceramics were fabricated with x(= Li) substitution by two-step sintering method, and their physical characteristics were investigated. When Li substitution was added to the ceramics, piezoelectric constant (d33) and electromechanical coupling factor (kp) were rapidly reduced. However, mechanical quality factor (Qm) was enhanced. For the KNN-BNZ((K,Na)(Nb)O3–(Bi,Na)(Sr)ZrO3) ceramics with Li(x) = 0 substitution, the best physical properties of d33 = 300 [pC/N], kp = 0.40, Qm = 33 and dialectic constant (εr) = 2430 were shown, respectively. Additionally, the KNN-BNZ ceramics with Li(x) = 0.02, the d33 of 246[pC/N], the kp of 0.37, the Qm of 42 and the εr of 2090 appeared, which were suitable for the low-loss piezoelectric actuator.

Role of Zn in modification of electronic and optical properties of c-SrZrO3: a computational insight

In this article, a DFT study is carried out to explore the electronic, structural and optical properties of SrZrO3 (SZO). Zn is doped at Sr site in minimum quantity to explore the minimal effect of Zn on electronic behaviour and its impact on other properties. For investigation of these properties, Ultrasoft pseudopotentials (USP) and Generalized Gradient Approximation suggested by Perdew, Burke, and Ernzerhof (GGA-PBE) functional is executed. The inclusion of Zn at Sr site in SZO affects the electronic and optical properties significantly. Band gap was expressively reduced from 3.315 eV to 2.618 eV which has direct impact with interacting energies. The nature of band gap for both intrinsic and doped systems remain indirect which means Zn inclusion did not affect the nature of band gap. The change in electronic properties due to addition of impurity leads towards change in optical properties. All the optical properties including complex dielectric function, absorption spectra, reflection coefficient, refractive index and extinction coefficient were calculated. The results showed a clear red shift in the absorption spectra along with peak shifting from 2.98 eV to 0.63 eV and the refractive index obtained for pure material is 2.13 which then altered to 2.45 due to doping. Doping of zinc in SZO significantly alter the electronic and optical properties and thus making it a valuable asset for optoelectronic devices.

Yb2O3‐Gd2O3 codoped strontium zirconate composite ceramics for potential thermal barrier coating applications

AbstractStrontium zirconate (SrZrO3) has been considered as a promising thermal barrier coating (TBC) material for application in gas turbine engines; however, the phase transition problem limits its application. In this study, an Yb2O3 and Gd2O3 codoped SrZrO3 system with excellent properties was reported. Yb2O3‐Gd2O3 codoped SrZrO3 ceramic powders [Sr0.8(Zr0.9Yb0.05Gd0.05)O2.75, SZYG/YGZO], [Sr(Zr0.9Yb0.05Gd0.05)O2.95, SZYG] and pure SrZrO3 (SZO) powders were produced by a conventional solid‐state reaction method. The XRD and Raman results show that, the composite SZYG/YGZO ceramics consist of the SZO and Yb0.5Zr0.5O1.75 phases with a low thermal conductivity of ~1.3 W/(m·K) at 1000°C, which is at least 40% lower than that of the SZO ceramics. The TG‐DSC results show that the SZYG/YGZO ceramics have no phase transition in the temperature range of 600 to 1400°C. The thermal expansion coefficient of the SZYG/YGZO ceramics reaches 10.9 × 10−6 K−1 (1250°C). In addition, the fracture toughness of the SZYG/YGZO ceramics increases by more than 30% compared with the SZO ceramics, and this can be attributed to the presence of the Yb0.5Zr0.5O1.75 phase.

An explicit and novel structure, lattice dynamics, and photoemission of La-doped nanocrystalline SrZrO3 perovskite

As no complete and comprehensive studies have been previously reported for La-doped nanocrystalline SrZrO3 (SZO), we researched herein a detailed investigation for pure and La-doped samples. A modified solid-state reaction process, including successive cycles of milling and sintering at high temperature, was followed to produce SZO and Sr0.9La0.1ZrO3 (SLZO) powdered ingots. Rietveld analysis of X-ray diffractometer data predicts that the two samples exhibit orthorhombic structure with an increase in crystallite size by ~25% for doped sample. A great reduction in Raman modes intensity (~60%) and an annihilation of several vibration modes were detected using Raman spectroscopy. The degree of ordering on the B-site was recorded to be higher in La-doped sample. According to ultraviolet–visible (UV–Vis) absorption, a decrease in the optical gap width (E g) from 4.40 eV to 4.21 eV was achieved by La incorporation due to the presence of additional defect states such as oxygen and Sr vacancies at the band edge. The process of electron–hole recombination was studied using photoluminescence (PL) spectroscopy. Deconvolution of PL spectra yielded four emission bands: one green band, one blue band, and two violet bands. Highly intense violet emission at λ = 393 nm approximately five times greater than that detected for pure SZO is realized as La3+ substitutes for Sr2+. Such property nominates SLZO for technological applications requiring highly intense violet emission, e.g., light-emitting diodes.

Piezoelectric characteristics of inorganic 0.965(Na, K, Li)(Nb, Sb)O3–0.035(Bi, Na)(Sr)ZrO3 ceramics doped with Fe2O3 for actuator

In this experiment, 0.965(Na,K,Li)(Nb,Sb)O3–0.035(Bi,Na)(Sr)ZrO3 ceramics were fabricated with Fe2O3 addition, and their piezoelectric characteristics were investigated. When Fe2O3 was added to the ceramics, d33and kp were decreased. However, Qm was increased. At the NKN-BNZ ceramics with 0.1 wt% Fe2O3, the d33, kp, Qm, and εr were optimized as 263[pC/N], 0.450, 51.94, 1978, respectively.

Numerical Simulation of the SrZrO3 Formation in Solid Oxide Fuel Cells

The Ce1−xGdxO2−δ (CGO) interlayer is a common reaction barrier layer employed in solid oxide fuel cells (SOFCs), to prevent chemical reactions between the (La1−xSrx)(Co1−yFey)O3−δ (LSCF) cathode and the Y2O3-stabilized ZrO2 (YSZ) electrolyte. However, even with the existence of the CGO layer, formation of SrZrO3 (SZO) insulating phase can still take place, causing cell degradation. Considering there have already been a large amount of experimental investigations conducted on the above degradation phenomenon, the current work is attempting to numerically model the process. A simplified numerical model of SZO formation at the YSZ–CGO interface is constructed. Based on the thermodynamic information and diffusion kinetics of the YSZ–CGO–LSCF system from the literature, the interdiffusion between YSZ and CGO, the Sr diffusion through the CGO layer, and the formation of SZO at the YSZ–CGO interface are modelled, reproducing the experimental data well. Limitations of the current modeling work are further discussed.

Innovative synthesis and properties of Fe doped nanocrystalline strontium zirconate for the development of visible light driven photocatalyst

Abstract Studies on the band gap engineering for photocatalysis and photovoltaic applications in SrZrO3 (SZO) being not explored. Here, we demonstrated a modified solid state reaction technique to prepare nanocrystalline perovskite with formula SrZr0.9Fe0.1O2.955 (SZFO). Phase analysis by X-ray powder diffractometry revealed the formation of only one orthorhombic phase with smaller crystallite size and enhanced lattice strain as Fe substitutes at Zr site. The availability of SZFO under study for the development of visible light driven photocatalysts was examined through diffused reflectance measurements. For the first time, a shift of the absorption edge to longer wavelength (red region) was observed. A narrowing of the optical band gap (Eg) to its half value (2.23 eV against 4.4 eV for pure sample) was achieved by Fe doping. Light absorbance was also found to drastically increase covering the UV-red region. These changes arose due to the distribution of Fe localized states at the O2p band edge and inside the forbidden gap. The effect of Fe incorporation was also examined by Raman and Mossbauer spectroscopies. Raman studies confirmed the presence of disorder and compositional fluctuations as Fe substitutes at the Zr site. Mossbauer analysis proved the presence of abundant Fe3+ (90%) and few Fe4+ species with distorted octahedral sites. The resultant oxygen deficiency balancing the charge neutrality was calculated. The detected ferromagnetic character was attributed to both super exchange and double exchange interactions. Works are in progress for further tuning of the band gap in SZFO as a promising material for photocatalytic and photovoltaic applications.