Co-doped TiO2 Thin Films Research Articles

Al-Mg co-doped TiO2 thin film as a promising ETL for perovskite solar cells: An experimental and DFT investigation

Solar cells offer a potential solution to the energy crisis, and perovskite solar cells are the latest frontrunner. However, low electrical conductivity of TiO2 ETL serves as a bottleneck to its efficiency. In this study, Al-Mg co-doped anatase thin films are prepared by one-step spin coating method and then characterized to tackle this problem. XRD results show that doping leads to smaller crystallite size and decreased interplanar spacing, but increases the lattice strain and dislocation density. AFM images reveal that Al-Mg co-doping increases surface roughness. Surface morphology of the co-doped film is good, covering the whole substrate uniformly without any pinholes. XPS results ensure that the desired composition is achieved. UV–vis spectroscopy data show that optical bandgap increases with Al-Mg co-doping, leading to the highest bandgap for Ti0.87Mg0.1Al0.03O2, which also has the highest transmittance peak, reaching 90 % in the visible region. Urbach energies are also calculated to get a better estimate of the effective bandgaps. Band edge positions are calculated using Mulliken’s electronegativity, demonstrating improved band alignment due to Al-Mg co-doping. The bandgap trend is further corroborated with DFT + U simulations, which show that calculated bandgaps match the experimentally obtained optical bandgaps. Additionally, density of states reveal that Ti 3d orbital dominates the conduction band and O 2p orbital dominates the valence band, with hybridization taking place between different orbitals. Four-point probe test demonstrates that Al-Mg co-doping leads to a consistent decrease in sheet resistance of the thin film. Better band alignment and higher visible light transmittance combined with enhanced conductivity indicate that Al-Mg co-doped anatase thin film has high potential as an ETL for perovskite solar cells.

Probing interface structure and cation segregation in (In, Nb) co-doped TiO2 thin films

Atomic-scale exploiting interfacial structure and cation distribution in doped TiO2 thin films possessing a polymorphic structure is of great importance for understanding their film-growth behavior and the structure-property relationship. Here, by applying advanced electron microscopy imaging, we have revealed the atomic-scale microstructure of TiO2 thin films co-doped with In and Nb (TINO) prepared on (001) LaAlO3 substrates by pulsed laser deposition. We determined that the TINO slabs with a brookite-typed structure (B-TiO2) form in the anatase-typed TINO (A-TiO2) film matrix with the crystallographic orientation relationship of (1¯12)[110]A-TiO2//(010)[001]B-TiO2. Besides the polymorphic phase boundary, interface structures including the {112}〈110〉-typed twin boundaries (TBs) in the A-TiO2 films and the (010) stacking faults (SFs) in the B-TiO2 slabs have been characterized. Cation (In and/or Nb) segregation and structure relaxation occur at the TBs and the SFs, which is energetically favorable corroborated by density functional theory calculations. Additionally, the cation segregation in the SFs leads to the formation of a new structure locally. Our findings provide a better understanding of interface structure, cation segregation, and phase formation in the doped-TiO2 polymorph materials.

Photocatalytic Activity and Mechanical Performance of O and N Co-doped TiO2 Thin Films

Photocatalytic Activity and Mechanical Performance of O and N Co-doped TiO2 Thin Films

Preparation and characterization of TiO2 thin film electrode for optoelectronic and energy storage Potentials: Effects of Co incorporation

In this study, thin film samples of undoped and Co-doped titanium oxide (TiO2) nanostructures were deposited on conducting ITO glass substrate. Influence of Co-dopant on TiO2 thin film for potential application in optoelectronic and supercapacitor devices was investigated. Microstructural studies revealed Co-doped TiO2 films possess fewer and narrower pores. Particles of the Co-doped TiO2 films are relatively larger, closely packed without any observable pin hole or crack. Increased dopant concentrations also improved the crystallinity and average grain sizes of the films but with slight distortions in their crystal lattices. Films’ crystal sizes lied between 47.51 and 57.23 nm. Elemental composition study confirmed the presence of all elements attributable to the films accordingly. Optical studies demonstrated the films’ high transparency across the visible light spectrum and that it is dependent on dopant concentration. Red shift towards higher wavelengths is observed in the absorption band edges upon dopant increasing concentration. The result also led to tunning of bandgaps and Urbach energies of TiO2 structure from 3.28 to 3.22 eV and 2.37 to 1.95 eV, respectively. The electrochemical properties of the deposited Co-doped and pure TiO2 thin films were investigated with the aid of analyses of cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopic (EIS) studies. The study showed that the film electrodes demonstrated appreciable high-rate energy storage capability and stability. It also revealed enhanced areal capacitance and capacity of 15.86 mF cm−2 and 9.19 mAh cm−2, respectively. The study demonstrated successful coating of the Co-doped TiO2 nanostructures on ITO glass substrate and unveiled the influence of cobalt dopant on some properties of TiO2 thin film suitable for application in optoelectronics and supercapacitor.

Influence of Thickness on the Structural, Morphological and Optical Properties of Co-doped TiO2 Thin Films Prepared by Sol-Gel Method

TiO2-based materials have high strength and suitable electronic properties that make TiO2 widely used. In this research, Co-doped TiO2 thin films were created through the sol-gel spin-coating method. The deposition process was conducted 3 times to prepare 1 to 3 layers. The structural, morphological, and optical properties of Co-TiO2 thin films were explored by XRD, SEM, and UV-VIS analyses. The prepared films were amorphous without a crystalline structure. SEM images demonstrate highly uniform particles on the surfaces. With the rise of thickness, nanoparticles get closer, and the particle size decreases. EDS spectra verify the existence of Ti, O, and Co in all samples. The transparency of thin films was reduced by increasing the thickness. Bandgap energy decreased with increasing the deposition layers, while Urbach energy increased.

Zn and N Codoped TiO2 Thin Films: Photocatalytic and Bactericidal Activity.

We explore a series of Zn and N codoped TiO2 thin films grown using chemical vapor deposition. Films were prepared with various concentrations of Zn (0.4-2.9 at. % Zn vs Ti), and their impact on superoxide formation, photocatalytic activity, and bactericidal properties were determined. Superoxide (O2•-) formation was assessed using a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium sodium salt (XTT) as an indicator, photocatalytic activity was determined from the degradation of stearic acid under UVA light, and bactericidal activity was assessed using a Gram-negative bacterium E. coli under both UVA and fluorescent light (similar to what is found in a clinical environment). The 0.4% Zn,N:TiO2 thin film demonstrated the highest formal quantum efficiency in degrading stearic acid (3.3 × 10-5 molecules·photon-1), while the 1.0% Zn,N:TiO2 film showed the highest bactericidal activity under both UVA and fluorescent light conditions (>3 log kill). The enhanced efficiency of the films was correlated with increased charge carrier lifetime, supported by transient absorption spectroscopy (TAS) measurements.

Influence of Fe3+ ion doping on the luminescence emission behavior and photocatalytic activity of Fe3+, Eu3+-codoped TiO2 thin films

Abstract Thin films of Fe3+ doped TiO2:0.01Eu3+ nanoparticles were coated by sol-gel spin coating technique on glass substrates. The studies carried out by using X-ray Diffractometer, SEM-EDX, HRTEM, spectroscopic ellipsometer, Raman, EPR, UV–Vis, and fluorescence spectrometer techniques. The crystalline structure and phase formation of Fe doped TiO2:0.01Eu3+ nanoparticles were investigated using X-ray Diffractometer. The HRTEM pictures of 3%, and 5% Fe doped TiO2:0.01Eu3+ films confirmed that the particle size is about 11 nm and 9.5 nm respectively. Raman spectroscopy was used to study the phase identification and vibrational modes present in Fe, Eu codoped TiO2 films. The band gap declined with cumulative amount of Fe3+. The EPR analysis endorses that the Fe3+ ions are successfully doped in the lattice of Titania by replacing Ti4+ ions and formation of oxygen vacancies and Ti3+ sites. With 393 nm excitation, the Fe doped TiO2:0.01Eu3+ nanoparticles show characteristic photoluminescence in the visible range. The strong luminescence emission at 614 nm is related to the 5D0 → 7F2 ED transition. The emission peak intensity declined with an increase in the amount of Fe3+. J–O and radiative parameters of Fe doped TiO2:0.01Eu3+ films obtained from the emission spectra. These nanophosphor films having significant CIE chromaticity coordinate (x, y) values with high color purity might have potential applications in solid-state display devices. The photocatalytic activity (PCA) of Fe, Eu codoped TiO2 nanostructured films were estimated using decolorization of methylene blue (MB) and methyl orange (MO). Fe, Eu codoped TiO2 films exhibit strong photocatalytic performance than undoped and single doped TiO2 films. The degradation efficiencies significantly increase with an increase in Fe3+ doping concentration reached maximum at 3%Fe doping and then reduces gradually at high concentrations due to the formation of recombination centers for charge carriers at a higher amount of Fe doping.

Effects of swift heavy ion-irradiation on magnetic properties of Co-doped TiO2

Ferromagnetic Co-doped TiO2 thin films at room temperature have been synthesized by RF sputtering and ion-irradiated with 100 MeV Au ions. The surface roughness of the film increases with increasing Au-ion fluence. Kerr microscopy measurements at room temperature give isotropic hysteresis loop with negligible coercivity, which gets modified into in-plane uniaxial magnetic anisotropy after anion fluence of 5×1011 ions/cm2. Further ion-irradiation reduced the coercivity of the film. X-ray magnetic circular dichroism (XMCD) measurements have been performed in total electron yield mode, to investigate the effects of ion-irradiation on magnetic properties of the Co-doped TiO2 thin films. From the XMCD analysis, we observed that the total magnetic moment of Co atoms in case of as-deposited film is 1.771±0.016μB. After the ion-irradiation it became 0.3818±0.014μB at room temperature.

Physical and photocatalytic properties of Nd codoped (Ag, Cu)TiO2 thin films

ABSTRACT Transparent co-doped TiO2 thin films have been fabricated by sol-gel dip-coating. The doping is achieved using low concentrations of neodymium (Nd), silver (Ag), and copper (Cu). A significant effect of doping is noticed on the morphology and optical properties of thin films. XRD analysis confirms the formation of a pure anatase phase with a deterioration of the crystallinity upon doping. The co-doped TiO2 thin films present larger crystallite size compared to other films. The surface roughness revealed by AFM increases from 0.9 nm for pure TiO2 up to 5 nm for doped thin films. UV-vis spectroscopy shows that the bandgap energy slightly decreased for co-doped Ag-Nd/TiO2 and Cu-Nd/TiO2. Photocatalytic degradation of MB significantly decreases upon doping. A mechanism based on combined effects of doping, annealing and nature of substrate is proposed to explain the photodegradation behaviour.

Hierarchical architecture of a superhydrophobic Cd-Si co-doped TiO2 thin film

Superhydrophobic coatings have various applications in the industries for successful control and removal of droplets from the surface. Hierarchical structures are promising to achieve a superhydrophobic surface. We fabricated a Cd-Si co-doped TiO2 hierarchical coating on the surface of a glass slide, exhibiting superhydrophobic properties. Cd-Si co-doped TiO2 thin films were prepared by a sol-gel dip-coating method. The morphology, the dominant TiO2 phase, and the crystal structure of the thin films were studied by the concentration of the Si dopant and the calcination temperature. Accordingly, the optical bandgap, surface chemical ligands, and surface topography of thin films also investigated. The lowest bandgap energy (3.23 ± 0.004 eV) was obtained for the sample with 5 wt% Cd and 20 wt% Si. Moreover, by increasing the calcination temperature of a sample with 5% Cd and 10% Si, the water contact angle was increased from 112.2° ± 6° to 168.5° ± 7°, due to the synergy effect of surface ligands and hierarchical structure.

Effect of Nickel–Zinc Co-doped TiO2 blocking layer on performance of DSSCs

Photovoltaic parameters in Dye-sensitized solar cells (DSSCs) are improved through the employment of Ni and Zn co-doped TiO2 thin film as a Photo-anode material in DSSCs. The TiO2 layers having different ratio of Ni and Zn were deposited over fluorine doped tin oxide (FTO) substrate using the spin coating technique. Organic dyes like mercurochrome (MC) dye were emerged out to use as sensitizer with TiO2 photoanode based DSSCs. The optical property of bare TiO2, NZT-20, NZT-40, NZT-60 and NZT-80 blocking layer prepared by using Ni and Zn-doped TiO2 with different doping concentrations were studied. The values of the bandgap were found to be 3.83, 3.78, 3.82 and 3.83 eV for TiO2 doped with Ni and Zn concentrations such as NZT-20, NZT-40, NZT-60 and NZT-80 respectively. Electrochemical impedance spectroscopy (EIS) was used to study the charge transfer resistance and interfacial capacitances that are present in a DSSCs. The EIS measurements are used to calculate values of charge transfer capacitance and resistance of all samples. The NZT-80 sample has a high value of resistance and capacitance so that it affects the photovoltaic performance of DSSC. The Blocking layer incorporated in NZT-80 sample gives 61% increased in the efficiency as compared to its bare TiO2 (without Co-doped Ni–Zn) photoanode.

Clustering-induced high magnetization in Co-doped TiO2

High magnetization materials are highly desirable for the development of advanced multifunctional magnetic applications. Co:TiO2 is a widely investigated diluted magnetic semiconductor (DMS) system which persists ferromagnetism to above room temperature. However, the magnetic moment observed in Co:TiO2 so far typically lays between 0.01 μB per Co atom to the Co bulk value, 1.7 μB/Co, while higher saturation magnetization (Ms) surpasses 2 μB/Co which has only occasionally been reported. The huge magnetization difference suggests formation of Co nanoclusters is poorly controlled and immensely dependent on growth parameters. In this work, 5 at% Co-doped TiO2 thin films on SrTiO3 substrate were deposited via pulsed laser deposition. By delicately choosing the deposition parameters, various sized Co nanoclusters are embedded into TiO2 thin films with unique surface nanostructures. The Co nanoclusters show metallic features, confirmed by X-ray photoelectron spectroscopy. Moreover, the thin films exhibit excellent cluster-dependent Ms, reaching 2.5 μB/Co under optimal parameters. This work provides an effective approach to design high magnetization thin films with various surface morphology.

Deposition of TiO2 Multilayer Thin Films Doped with Cobalt and Studying the Effect of Annealing Temperatures and Number of Layers on the Structural and Morphological of Thin Films

The effect of the number of layers and annealing temperatures on the structural and morphological properties of Co-doped TiO2 thin films which were fabricated by solgel spin-coating method was explored. The spin-coating process was repeated up to 4 times to gain 1- to 4-layer films. The 2-coated layer films were annealed at 523 K and 723 K for 60 min. The XRD analysis showed the amorphous structures for as-deposited multilayer films, which could be suggested that cobalt ions do not lead to the formation of crystalline phase of TiO2 films without annealing process. Anatase phase of TiO2 with tetragonal crystal structure was observed for films annealed at 723 K. The FESEM results indicated spherical nanoparticles which were risen in density with increasing the number of layers and grew when the annealing temperature was enhanced. RMS roughness was calculated by AFM analysis. It was found that RMS roughness of the films was increased by increasing the number of coating layers and annealing temperatures. The increase in roughness is desirable for solar cell applications.

Structural and Microstructural Effects of Mo3+/Mo5+ Codoping on Properties and Photocatalytic Performance of Nanostructured TiO2 Thin Films

Mo3+/Mo5+ equally codoped TiO2 thin films (0.050–0.100 mol % individually) were fabricated by spin coating on polished fused silica glass substrates followed by annealing at 450 °C for 2 h. The hig...

Intervalence charge transfer and thermodynamic effects on the photocatalytic performance of Fe/Mo single and codoped TiO2 thin films

Fe/Mo single doped and codoped TiO2 thin films were spin coated on polished fused silica substrates and annealed in air at 450 °C for 2 h. The XPS data for the anatase thin films were distinctive in showing that Fe-doping caused Ti4+ reduction, Mo-doping caused Ti4+ oxidation, and codoping did not alter the Ti valence. The XPS data also showed that the precursor valences of Fe3+ and Mo5+ were reduced upon annealing. Analysis of the potential roles of thermodynamics and intervalence charge transfer (IVCT) demonstrates that the latter drives the equilibria both in solution and during annealing. Photocatalytic performance testing indicated that Fe-doping was slightly deleterious, Mo doping had a consistent positive effect, and codoping exhibited a clear negative trend as a function of doping concentration. These results are interpreted in terms of the effect of IVCT on the matrix valence, dopant valences, and charge carrier trapping. Fe doping exhibited reduced performance because both matrix Ti(4−x)+ and dopant Fe(3−y)+ acted as electron traps. Mo doping exhibited enhanced performance because the matrix Ti(4+x)+ acted as a hole trap and the dopant Mo(5−x)+ and Mo(4−x)+ acted as electron traps, thereby promoting charge separation. Codoping exhibited a clearly detected negative trend on the performance because, while Ti4+ played no role, Fe(3−y)+, Mo(5−x)+, and Mo(4−x)+ all acted as traps for the majority charge carrier electrons.

Modeling the response of optical and hydrophobic properties of codoped TiO2 thin films

In the current research, the effect of Cd- and Sr-codoped TiO2 thin films on bandgap and the degree of wettability were studied using a statistical method. The selected parameters were two types of different dopants, including Sr and Cd, and the weight percent of each dopant in the range of 0 to 20%. The experiments were designed using the response surface methodology in order to model and analyze the effect of selected parameters on responses. The responses included bandgap energy and contact angle. Analysis of variance was used to validate adequacy of the proposed mathematical models. The obtained mathematical models were useful not only for predicting the bandgap and contact angle with higher accuracy but also for selecting optimum dopant parameters to achieve the desired bandgap and hydrophilic properties. By using the optimized conditions resulted from the models, minimum bandgap and contact angle were calculated 2.24 eV and 3.82°, respectively, where the optimum condition of selected parameters obtained 19 and 2.50 wt% for Cd and Sr, respectively.

Preparation and characterization of nanostructured S and Fe co-doped TiO2 thin film by ultrasonic-assisted spray pyrolysis method

Nanostructured TiO2 and S and Fe co-doped TiO2 thin films with high transparency were prepared on glass substrate through ultrasonic-assisted spray pyrolysis technique. The effects of doping on morphological, optical and structural properties of TiO2 were studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), photoluminescence spectroscopy, Raman spectroscopy, and UV-visible absorption spectroscopy techniques. Because of the high uniformity and monodispersity of the prepared thin films, they have high visible light transparency. All of the prepared thin films have anatase crystal structure, however, introduction of the dopants, especially S dopant, in the lattice of TiO2 creates some structural defects in the TiO2. Because of the presence of defects as charge trapping center in the structure of the doped TiO2samples, these thin films have lower electron–hole recombination rate than undoped TiO2. Furthermore, simultaneous doping of S and Fe considerably narrows the band gap energy of TiO2.

Characterization of N, F Co-Doped Mixed-Anion TiO2 Thin Films Prepared By Reactive Pulsed Laser Deposition for Visible-Light Responsive Photocatalyst

Introduction The study of water splitting by photocatalyst as the method of directly producing hydrogen from water has been reported in 1972, well-known as “Honda-Fuzishima effect”. Conventional TiO2 material can produce hydrogen under only ultraviolet light and the its production rate is still low. In order to use TiO2 under visible light, the anion doping is one of the effective solution. In this study, photocatalytic N, F-doped TiO2 thin film was synthesized by the responsible pulsed laser deposition(PLD) technique. Nitridation and fluoridation of TiO2 were simultaneously conducted with PLD under O2/N2/NF3 gas. Experimental TiO2 thin film was prepared by pulsed laser deposition (PLD). A Nd:YAG laser operating at a wavelength of 532 nm was focused on a sintered TiO2 target. We used a chamber which can be evacuated to a base pressure of 5.0 x 10-4 Pa by means of a turbo-molecular pump. When depositing TiO2 thin film, the total pressure of the mixed gas was fixed to 5 Pa. FTO (Fluorine doped tin oxide) was used as the glass substrate for film deposition. The substrate temperature was changed from room temperature to 400℃. The target (φ10) was produced by sintering the Rutile TiO2 powder at 1000℃ for 12h in air. Structural analysis of TiO2 is carried out by XRD (X-ray diffiraction) and XAFS (X-ray Absorption Spectroscopy). Especially, the product identification was observed by XRD with parallel beam method at SPring-8 BL02B2. An incident angle of X-ray is 0.1o and wavelength of X-ray is 0.7Å. Measurement of the absorption edge of Ti K was carried out by XAFS with electron yield method. In addition, for defining of the flatband level and bandgap carried out by UV-vis and AC impedance measurement. Photoelectrochemical measurements were conducted in an aqueous Na2SO4 solution (0.1 M, pH=9) using a potentiostat (Hokuto Denko HSV-110) connected to the photocatalyst-deposited FTO glass as a working electrode an Ag/AgCl reference electrode (in saturated KCl aqueous solution), and Pt wire as a counter electrode. The solution was purged with Ar gas for 30 min. To measure photocurrent responses, intermittent visible light (420 < λ < 800 nm) was applied to the working electrode with a Xe lamp (300 W, output current: 20 A). Result & Discussion Fig. 1 shows that XRD results under various gas atmosphere. In the case of under the O2 atmosphere, Anatase/Rutile TiO2 composition was observed. Under the N2 atmosphere, TiN was observed and under the NF3 atmosphere, Anatase TiO2 was observed. Under the N2 and N2/NF3 atmosphere, FTO substrate was decomposed. Under the O2/N2/NF3 atmosphere, the decomposition of the substrate was suppressed while the compounds derived from Ti couldn’t be observed. These results indicated that O2 gas was necessary for depositing TiO2 by suppressing of substrate as well as supplementation of the oxygen defects. Fig. 2 shows that the visible light response as a function of the photocurrent and voltage. By switching Xe lamp on/off per 3 second, the increase and decrease of current density was observed over 0.4 µA cm-2. The photocurrent response under visible light was observed for the atmosphere of O2/N2/NF3 and O2/N2 while that of O2/NF3 was not. In addition, the photocurrent was larger for the materials prepared under O2/N2/NF3 than O2/N2. UV-vis diffuse reflectance spectrum indicated that N, F-doped TiO2 showed a wide absorption band in visible region in contrast to a narrow one of N-doped TiO2. This extended absorption band of N, F-doped TiO2 in the visible region allowed the materials to improve the efficiency of the catalytic reactions such as water oxidation. Conclusion It is necessary that O2 gas to suppress substrate decomposition and compensate oxygen defect. PLD performed under O2/N2/NF3 mixed gas could successfully incorporated N3- and F- into TiO2 matrix. The visible light response of co-doping of N3- and F- was better than N3- single doping. It was subjected to the UV-vis measurement, the N3-, F- co-doped TiO2 thin film has wide absorption band of a visible light, which was considered to have led to a visible light absorption. Reference 1) A. Nakada et al., J.Mater. Chem. A, 2017, 5, 11710-11719. 2) K. Maeda et al., J. Phys. Chem. C, 2007, 111 (49), 18264–18270. Figure 1

Lifetime Enhancement of Visible Light Induced Photocharges in Tungsten and Nitrogenin situCodoped TiO2:WN Thin Films

We report on one-step in situ codoped TiO2 thin films synthesized by cosputtering. The purpose of this acceptor–donor passivated codoping approach is to overcome the optoelectronic limitations that arise for monodoped TiO2 in photocatalytic applications. To evaluate these added benefits, the TiO2:WN thin films were characterized by different techniques. X-ray diffraction patterns and X-ray photoelectron spectral analysis revealed that both N and W dopants are mostly present in the desired substitutional locations. Additionally, the codoping approach was found to reduce the internal strain and defect density of the TiO2:WN films as compared to their monodoped TiO2:N counterparts. This defect reduction is confirmed via photocharge lifetime variation obtained using visible light flash photolysis time-resolved microwave conductivity measurements (FP-TRMC). Photocharge lifetime analysis indicated the presence of three distinct decay processes: charge trapping, recombination, and surface reactions. These charac...

Effect of doping concentration on Nd-related photoluminescence in TiO2 with Al co-doping

Nd doped, Nd-Al co-doped anatase phase TiO2 thin films were fabricated on silicon substrates by laser ablation and post annealing. The result of measuring PL spectra showed intense emissions from a luminescent centre of Nd3+ ions in these thin films. The luminescence of Nd-Al co-doped samples were stronger and broader than only Nd doped samples. Doping concentration of Nd determined suitable co-doping concentration of Al and post annealing temperature. Also there is the difference of shape of the PL spectra which indicates that the difference of local fine structure around Nd. Based on these facts, XAFS spectra was measured and suggested that the coordination around Nd was changed by this Al-co-doping.