Piezoresistive Ni:a-C:H thin films containing hcp-Ni or Ni3C investigated by XRD,EXAFS, and wavelet analysis

Ni:a-C:H thin films obtained by reactive sputtering processes were investigated using EXAFS and subsequent wavelet analysis. Depending on overall thin film deposition conditions, the clusters of Ni in Ni:a-C:H can appear as fcc-Ni or as a non-fcc-Ni phase, such as hcp-Ni or Ni₃C. While hcp-Ni and Ni₃C are hardly distinguishable by XRD, the EXAFS analysis can reveal if carbon is the nearest neighbour of Ni or not, thus if Ni₃C is present or hcp-Ni. Our study showed that wavelet transformation analysis of the EXAFS data is necessary to discriminate clearly between hcp-Ni and Ni₃C regarding the presence or absence of carbon coordination shells around the X-ray absorbing Ni atoms. Furthermore, we are confident to have identified Ni₃C in our thin films, however, we cannot exclude the possibility of the co-existence of hcp-Ni. Finally, calculations of XRD peaks of hcp-Ni and Ni₃C showed that a discrimination of these two crystal phases might be feasible when the crystallite size is increased beyond 40 nm.     

High-pressure and high-temperature synthesis of stable SxCo3.6Ni0.4Sb12 skutterudite compounds

Compared to Te, Ni is found in abundance in the earth's crust. At the same time, the mechanical properties of Ni atom-substituted skutterudite are significantly improved. In this study, a series of S-filled Ni-substituted skutterudite compounds were synthesized by a high-pressure and high-temperature (HPHT) method in the synthesis pressure range of 1.0–3.0 GPa. The phase composition, microscopic morphology, and electrothermal transmission properties of the S_xCo_3.6Ni_0.4Sb₁₂ (x = 0, 0.05, 0.10, 0.20) samples were systematically characterized. Phase composition analysis showed that the introduction of S atoms into the intrinsic pores of skutterudite can improve the solid solution limit of Ni atoms in the Co sites of skutterudite. The filling limit of S increased with the synthetic pressure. Moreover, microscopic morphology analysis revealed that the filling of S atoms inhibited the growth of grains. A large number of lattice fringes in different directions were found in the sample, containing abundant microstructures such as lattice distortions and dislocation defects. Compared with the synthesized samples, S_0.05Co_3.6Ni_0.4Sb₁₂ synthesized at 1.0 GPa had a maximum room temperature power factor of 7.98 × 10^?4 Wm^?1K^?2. The electrical properties of S_0.05Co_3.6Ni_0.4Sb₁₂ samples stored for 6 months without any protective measures were tested at room temperature. No obvious changes in performance were observed, which proved that the HPHT method can synthesize stable samples. After several thermal cycles, the electrical properties of the S_0.05Co_3.6Ni_0.4Sb₁₂ sample was tested for variable temperature, and it was found that the sample still had good stability. How the substitution of S atoms with Ni atoms reduces the lattice thermal conductivity can be explained by fitting the Callaway model. The S_0.05Co_3.6Ni_0.4Sb₁₂ sample synthesized at 1.0 GPa had a maximum zT value of 0.46 at the test temperature of 773 K, which decreased to 0.43 after multiple thermal cycles at the same temperature.     

Structural and Electrical Properties of Ni‐Substituted Mg‐Mn Nanoferrite by Coprecipitation Route

Ni²⁺ ions doped on Mg_0.40Mn_0.60‐xNi_xFe₂O₄ compositions with 0.00 ≤ x ≤ 0.60 have been synthesized by coprecipitation method and taken for the present work to study the dielectric properties and impedance characterization using the XRD and electrical measurements. The X‐ray diffraction and FT‐IR revealed that the ferrite has single‐phase cubic spinel structure. The calculated particle size from XRD data verified using SEM as well as AFM. These photographs show that the ferrites have crystalline size in the range of 20–50 nm. It was observed that the particle size decreased and Ni concentration increased. The dielectric constant and dielectric loss decreased with increase in nonmagnetic Ni²⁺ ions. Electrical properties indicate that synthesized nanoferrite particles have high resistivity.     

Tailoring Ni3ZnC0.7/graphite heterostructure in N-rich laminated porous carbon nanosheets for highly efficient microwave absorption

Bimetallic transition carbide nanoparticles (Ni₃ZnC_0.7) encapsulated with graphitic shells were successfully embedded into N-rich laminated porous carbon nanosheets (NC–ZnNi_1.5) by one-step pyrolysis of bimetallic organic frameworks. It was found that C atoms penetrated octahedral interstitial spaces of the Ni lattice to form Ni₃ZnC_0.7. The charge states and distribution of metal atoms were influenced by the interstitial C atoms, which promoted polarization relaxation and facilitated dielectric loss. Simultaneously, the volatilization of Zn influenced recrystallization and rearrangement of the crystalline domains, facilitated graphitization and established a 3D conductive network to optimize the conductive loss. Besides, multi-level heterogeneous interface and nitrogen doping also further optimized the impedance matching. Benefiting from these advantages, the minimum reflection loss of NC-ZnNi_1.5 was −69.1 dB at 12.7 GHz, and the effective absorption bandwidth was 6.5 GHz. The mechanism of bimetallic carbide's dielectric loss was explained in detail, providing a new pathway for the development of multi-component carbon-based microwave absorbers in the future.     

Grain-orientation-engineered PMN-10PT ceramics for electrocaloric applications

The electrical properties of ferroelectric materials depend on their crystal orientations. The 〈001〉 and 〈111〉 textured 0.90Pb(Mg_1/3Nb_2/3)O₃–0.10PbTiO₃ (PMN-10PT) ceramics were synthesized using a template grain growth method and conventional solid sintering process. The Lotgering factors of the 〈001〉 and 〈111〉 textured PMN-10PT ceramics with 5% anisotropic BaTiO₃ (BT) precursors were 95% and 87%, respectively. The influence of grain orientation direction on dielectric properties was investigated, revealing that the permittivity of textured PMN-10PT ceramics (ε_r〈001〉 = 12200, ε_r〈111〉 = 11800) was lower than that of random ceramics (ε_r = 18700). Electrocaloric (EC) responses of the random and textured samples were analyzed using an indirect polarization-deduced method based on Maxwell's equations. When the applied field was 50 kV cm⁻¹, the 〈111〉 textured ceramics exhibited an enhanced adiabatic temperature change of 1.30 K, which was 20% higher than that of the random samples. In addition, the EC performance of the 〈111〉 oriented samples was significantly improved compared to that of the 〈001〉 oriented ones. This work characterizes the grain-orientation-dependent EC responses in the PMN-PT system, which would be a promising approach to EC response improvement in ferroelectric ceramics.     

Microstructural evolution and growth kinetics of interfacial reaction layers in SUS430/Ti3SiC2 diffusion bonded joints using a Ni interlayer

Ti₃SiC₂ ceramic and SUS430 stainless steel (SS) were successfully joined by a solid diffusion bonding technique using Ni interlayers. Diffusion bonding was performed in the temperature range of 850 °C–1100 °C under vacuum. The interfacial reaction phase, morphology evolution, growth kinetics and tensile strength were systematically investigated. In all cases, the inter-diffusion and reaction between Ti₃SiC₂ and SS can be effectively prevented by Ni foil, and the good transition in the joint benefit to the sound joining. The interface in the joints adjacent to SS matrix was composed of γ solid solution and a small amount of σ intermetallic compound. The compounds in the Ni/Ti₃SiC₂ interface was Ni/Ni(Si)/Ni₃₁Si₁₂ + Ni₁₆Ti₆Si₇ + Ti₃SiC₂ + TiC_x/Ti₂Ni + Ti₃SiC₂ + TiC_x/Ti₃SiC₂, which formed by the inter-diffusion and chemical reactions between Si and Ni atoms. The diffusion mechanism and reaction mechanism were interrelated, and decided the width of each reaction zones. Furthermore, the diffusion activation energy was 113 kJ/mol. The tensile strength increases with increasing the bonding temperature. The minimum and maximum strength of 32.3 MPa and 88.8 MPa were obtained from SUS430/Ni/Ti₃SiC₂ joints, which bonding experiments were carried out at 850 °C and 1100 °C, respectively.     

X‐ray photoelectron spectroscopy analysis of Ge–Sb–Se pulsed laser deposited thin films

Pulsed laser deposition was used to prepare amorphous thin films from (GeSe₂)_100?x(Sb₂Se₃)_x system (x = 0, 5, 10, 20, 30, 40, 50, and 60). From a wide variety of chalcogenide glass‐forming systems, Ge–Sb–Se one, especially in thin films form, already proved to offer a great potential for photonic devices such as chemical sensors. This system has a large glass‐forming region which gives the possibility to adjust the chemical composition of the glasses according to required physical characteristics. The chemical composition of fabricated thin films was analyzed via X‐ray photoelectron spectroscopy (XPS) and compared to energy dispersive spectroscopy (EDS) data. The results of both techniques agree well: a small deficiency in chalcogen element and an excess of antimony was found. The structure of as‐deposited thin films has been investigated by XPS. The presence of the two main structural units, [GeSe₄] and [SbSe₃] proposed by Raman scattering spectroscopy data analysis, was confirmed by XPS. Moreover, XPS core level spectra analysis revealed the presence of M–M bonds (M = Ge, Sb) in (Ge,Sb)–Ge–(Se)₃ and (Ge,Sb)–Sb–(Se)₂ entities that could correspond to Ge‐based tetrahedra and Sb‐based pyramids where one of its Se atoms at corners is substituted by Ge or Sb ones. The content of depicted M–M bonds tends to increase with introduction of antimony in the amorphous network of as‐deposited thin films from x = 0 to x = 40 and then it decreases. XPS analysis of as‐deposited thin films shows also the presence of the (Ge,Sb)–Se–(Ge,Sb) and Se–Se–(Ge,Sb) entities.     

Structural,spectral, dielectric and photocatalytic studies of Zr-Ni doped MnFe2O4 co-precipitated nanoparticles

In this study the Mn_1–2xZr_xFe_2−yNi_yO₄ nanoparticles fabricated by co-precipitation technique were investigated. Thermo-gravimetric analysis (TGA) exhibited the annealing temperature of the nanoparticles ~990 °C. Cubic spinel structure of Mn_1–2xZr_xFe_2−yNi_yO₄ nanoparticles was confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. Crystallite size was calculated by XRD data and found in the range of 32–58 nm. Photocatalytic activity of Mn_0.92Zr_0.04Fe_1.88Ni_0.12O₄/graphene nanocomposites was tested by degrading methylene blue (MB) under visible light irradiation. The MB was almost completely degraded in the presence of Mn_0.92Zr_0.04Fe_1.88Ni_0.12O₄-graphene nanocomposites under visible light irradiation. Dielectric parameters were also investigated in the frequency range 1×10⁶–3×10⁹ Hz. An overall decrease in the values of dielectric constant, dielectric loss and tangent loss was observed on account of the substitution of Zr and Ni with Mn and Fe cations.     

Preparation of a highly dispersed Ni2P/Al2O3 catalyst using Ni–Al–CO32 − layered double hydroxide as a nickel precursor

We now report a novel method for the synthesis of a Ni₂P/Al₂O₃-LW catalyst using Ni–Al–CO₃^2 − layered double hydroxide (Ni–Al–CO₃^2 −-LDH) as a nickel precursor and ammonium dihydrogen phosphate as a phosphorous precursor under microwave–hydrothermal (MWH) treatment for 20 min at 363 K. The catalysts were characterized by XRD, TPR, BET, CO uptake and XPS. MWH treatment can promote the formation of smaller and highly dispersed Ni₂P particles and a higher surface area of the catalyst. The Ni₂P/Al₂O₃-LW shows hydrodesulfurization activity of 99.3%, which was much higher than that found for the Ni₂P/Al₂O₃ catalyst obtained via an impregnation method.     

Effect of Ni2+ substitution on structural,magnetic, dielectric and optical properties of mixed spinel CoFe2O4 nanoparticles

Nanoparticles of Co_1−xNi_xFe₂O₄ with x=0.0, 0.10, 0.20, 0.30, 0.40 and 0.50 were synthesized by co-precipitation method. The structural analysis reveals the formation of single phase cubic spinel structure with a narrow size distribution between 13–17 nm. Transmission electron microscope images are in agreement with size of nanoparticles calculated from XRD. The field emission scanning electron microscope images confirmed the presence of nano-sized grains with porous morphology. The X-ray photoelectron spectroscopy analysis confirmed the presence of Fe²⁺ ions with Fe³⁺. Room temperature magnetic measurements showed the strong influence of Ni²⁺ doping on saturation magnetization and coercivity. The saturation magnetization decreases from 91 emu/gm to 44 emu/gm for x=0.0–0.50 samples. Lower magnetic moment of Ni²⁺ (2 µ_B) ions in comparison to that of Co²⁺ (3 µ_B) ions is responsible for this reduction. Similarly, overall coercivity decreased from 1010 Oe to 832 Oe for x=0.0–0.50 samples and depends on crystallite size. Cation distribution has been proposed from XRD analysis and magnetization data. Electron spin resonance spectra suggested the dominancy of superexchange interactions in Co_1−xNi_xFe₂O₄ samples. The optical analysis indicates that Co_1−xNi_xFe₂O₄ is an indirect band gap material and band gap increases with increasing Ni²⁺ concentration. Dispersion behavior with increasing frequency is observed for both dielectric constant and loss tangent. The conduction process predominantly takes place through grain boundary volume. Grain boundary resistance increases with Ni²⁺ ion concentration.     

Structural,microstructural, and magnetic studies of Y3Fe5-xNixO12 garnet nanoparticles

This paper reports the structural and magnetic properties of a series of Y₃Fe_5-xNi_xO₁₂ (x = 0, 0.05, 0.1, and 0.2) nanopowders synthesized by the citrate combustion method. We have discussed the change in different properties with the variation in calcination temperatures as well as the Ni ion substitution in yttrium iron garnet. X-ray diffraction study confirmed the desired garnet phase formation in all the calcined powders, and the crystallinity improved with an increase in calcination temperature. The crystallite sizes were observed in the range 47–52 nm and 84–94 nm for the samples calcined at 800 and 1000 °C, respectively. Scanning electron micrographs confirmed that the grains were in the nanometre range (132–170 nm) at 800 °C and increased (351–363 nm) at 1000 °C. Larger grains at high calcination temperature resulted in the enhanced saturation magnetization and a decrease in coercivity. Curie temperature (T_c) was observed in the range 558–560 K for all the calcined Y₃Fe_5-xNi_xO₁₂ samples. Nickel substitution for iron sites in Y₃Fe_5-xNi_xO₁₂ decreased the saturation magnetization and enhanced the coercivity. This could be related to the substitution of Ni ions for tetrahedral iron sites, which changed the magnetic exchange interactions of different lattice sites. The magnetic anisotropy constant (K) increases with the enhancement of calcination temperature, whereas it decreases with nickel ion substitution in Y₃Fe_5-xNi_xO₁₂. This study suggests that the structural and magnetic properties can be tuned by Ni substitution for the Fe ions in Y₃Fe₅O₁₂ garnets at different calcination temperatures, which make them promising candidates for various technological applications.     

Influence of mixing time during glycine–nitrate process on the structural properties and reducibility of a dual-phase Ni–Cu–Mn spinel catalyst

The potential of Ni–Cu–Mn spinels as methane reforming catalysts for hydrocarbon-fueled solid oxide fuel cell (SOFC) applications is highly dependent on its catalytic properties, particularly reducibility. The reducibility of a spinel-structured catalyst is often correlated with its structural properties and fabrication processes. In this work, the structural properties and reducibility of a Ni–Cu–Mn spinel catalyst was evaluated on the basis of mixing time during the glycine–nitrate process. Phase analysis results showed that Ni_0.4Cu_0.6Mn_2.0O₄ and (Cu, Mn)₃O₄ in normal or inversed spinel structures were observed in GNP-produced Ni–Cu–Mn spinel catalyst powders. Distortion in inverse spinel structures enhanced the reducibility of the spinel catalyst. Morphological analysis results showed that complete nitrate binding occurred at a minimum mixing time of 24 h and resulted in homogenous particle size distribution and uniform elemental distribution. Furthermore, the Ni–Cu–Mn spinel catalyst produced after 24 h of mixing was fully reduced at 450 °C. The reducing pattern of the Ni–Cu–Mn spinel catalyst produced after 24 h of mixing time showed strong metal–support interaction and the fast adsorption of reactants. These effects were due to either the distribution of divalent cations in octahedral sites or large amounts of bulk pores. In conclusion, a minimum mixing time of 24 h is sufficient to produce the desired structural properties and reducibility of Ni–Cu–Mn spinel catalysts for SOFC applications.     

Chemical Synthesis,Sintering and Piezoelectric Properties of Ba0.85Ca0.15 Zr0.1Ti0.9O3 Lead‐Free Ceramics

The preparation of Ba_0.85Ca_0.15 Zr_0.1Ti_0.9O₃ (BCZT) powders by wet chemical methods has been investigated, and the powders used to explore relationships between the microstructure and piezoelectric properties (d₃₃ coefficient) of sintered BCZT ceramics. Sol–gel synthesis has been shown to be a successful method for the preparation of BCZT nanopowders with a pure tetragonal perovskite phase structure, specific surface area up to 21.8 m²/g and a mean particle size of 48 nm. These powders were suitable for the fabrication of dense BCZT ceramics with fine‐grain microstructures. The ceramics with the highest density of 95% theoretical density (TD) and grain size of 1.3 μm were prepared by uniaxial pressing followed by a two‐step sintering approach which contributed to the refinement of the BCTZ microstructure. A decrease in the grain size to 0.8–0.9 μm was achieved when samples were prepared using cold isostatic pressing. Using various sintering schedules, BCZT ceramics with broad range of grain sizes (0.8–60.5 μm) were prepared. The highest d₃₃ = 410.8 ± 13.2 pC/N was exhibited by ceramics prepared from sol–gel powder sintered at 1425°C, with the relative density of 89.6%TD and grain size of 36 μm.     

Hydrodeoxygenation of p-cresol on unsupported Ni–P catalysts prepared by thermal decomposition method

Unsupported Ni–P catalysts were prepared from the mixed precursor of NiCl₂ and NaH₂PO₂ by thermal decomposition method, and their catalytic activities were measured using the hydrodeoxygenation (HDO) of p-cresol as probe. The effects of the H₂PO₂⁻/Ni^2 + molar ratio in the precursor and the thermal decomposition temperature on the catalyst purity, crystallite size and HDO activity were studied. The HDO of p-cresol on these Ni–P catalysts proceeded with two parallel pathways yielding methylbenzene and methylcyclohexane as final products. The higher HDO catalytic activity of the catalyst was attributed to its bigger crystallite size and purer phase of Ni₂P.     

Study of TiC/Ni3Al composites by laser ignited self-propagating high-temperature synthesis (LISHS)

TiC/Ni₃Al composites have been obtained in situ by laser ignited self-propagating high-temperature synthesis (LISHS) of an intimate mixture of compacted powders of elemental C, Ti, Ni and Al. Ignition temperature (T_ig) and combustion temperature (T_c) are investigated; the effects of Ni₃Al content on density, phase composition, microstructure of the reaction products and particle size of the synthesized TiC were studied. The results show the density of the products varies with Ni₃Al content, and a maximum value of density appears at 50 wt.% Ni₃Al; TiC and Ni₃Al are the two stable phases after SHS, TiC particle size decreases with the increasing of Ni₃Al content, however, the decreasing of grain size is unobvious when Ni₃Al content is over 60 wt.%.     

First-principles insights on anion redox activity in NaxFe1/8Ni1/8Mn3/4O2: Toward efficient high-energy cathodes for Na-ion batteries

In the search for high-energy cathode materials for Na-ion batteries (NIBs), Fe-doped layered transition metal oxides have been recently proposed as promising systems that can ensure improved reversible capacity at high working voltage. Exploiting the anionic redox chemistry in this class of materials represents a great advance for the energy storage community, but uncontrolled oxidation process can lead to the formation of unbound molecular oxygen, with detrimental effects on overall capacity and stability upon cycling. The higher TM–O covalency provided by Fe doping seems to prevent oxygen loss and ensure full capacity recovery. Understanding anionic processes and the underlying mechanism with atomistic details can reinforce the experimental efforts and help to outline rational design strategies for novel high-performing NIB cathodes. To this end, we present a state-of-the-art first-principles study on the P2-type Na_xTMO₂ (TM = Fe, Ni, and Mn—NFNMO) oxide. We compare structural and electronic features of stoichiometric (Na_xFe_0.125Ni_0.125Mn_0.75O₂) and Mn-deficient (Na_xFe_0.125Ni_0.125Mn_0.68O₂) NFNMO to identify and discuss the contribution of each element sublattice on charge compensation processes. Although Mn deficiency is predicted to increase the cathode working voltage, we find the charge compensation being mostly exerted by the Ni and Fe sublattices. Oxygen redox is unfold via the formation of superoxide species at low Na loads with a preferential breaking of more labile Ni–O bonds and binding to Fe atoms. Our calculations predict no release of molecular O₂ upon desodiation, thus highlighting the key role of Fe dopant that provides a good TM–O bond strength, preventing oxygen loss while still enabling anionic redox reactions at high voltages with extra reversible capacity.     

Nickel-containing magnetoceramics from water vapor-assisted pyrolysis of polysiloxane and nickel 2,4-pentanedionate

In this study, novel ferromagnetic Ni-containing silicon oxycarbide (SiOC–Ni) was successfully fabricated from a base polysiloxane (PSO) with the addition of nickel 2,4-pentanedionate. The resultant SiOC–Ni nanocomposite consists of in situ formed Ni nanocrystallites with a small amount of NiO uniformly dispersed in the amorphous SiOC matrix, and the corresponding nanocrystallite size increases with the increase of the pyrolysis temperature. The formation of nickel silicides (Ni_xSi_y) is completely suppressed by the effect of water vapor during the pyrolysis. The fundamental phase evolution process and mechanisms are explained. In an argon atmosphere, the SiOC–Ni materials pyrolyzed at 900°C are stable up to 1000°C with less than 6 wt% weight loss; they exhibit desirable electrical conductivity up to ~900°C with the highest electrical conductivity at ~247 S/m. This series of SiOC–Ni materials also demonstrates exciting ferromagnetic behaviors. Their new semiconducting behavior with soft ferromagnetism presents promising application potentials for magnetic sensors, transformers, actuators, etc.     

A chiral tetranuclear cubane-like [Ni4O4] complex: Synthesis,structure and low-temperature magnetic behavior

A tetranuclear cubane-like [Ni₄(EtOH)₃L₄] (H₂L = (s)-2-((1-hydroxy-3-methylbutan-2-ylimino)methyl)phenol) complex has been prepared by the reaction of nickel(II) acetate with chiral Schiff base compound H₂L. The X-ray crystal structure analyses revealed that the core of the cube was formed by four Ni(II) ions and four alkoxide oxygen atoms at alternating corners. The temperature (2–300 K) dependent magnetic susceptibility indicates it possesses a system with predominant ferromagnetic interaction.     

Layered NdBaCo2−xNixO5+δ perovskite oxides as cathodes for intermediate temperature solid oxide fuel cells

The effect of Ni substitution on the crystal chemistry, thermal and electrochemical properties, and catalytic activity for oxygen reduction reaction of the layered NdBaCo_2−xNi_xO_5+δ perovskite oxides has been investigated for 0 ≤ x ≤ 0.6. The oxygen content (5 + δ) and oxidation state of the (Co, Ni) ions in the air-synthesized NdBaCo_2−xNi_xO_5+δ samples decrease with increasing Ni content, accompanied by a structural transition from tetragonal (0 ≤ x ≤ 0.4) to orthorhombic (x = 0.6). Similarly, the thermal expansion coefficient (TEC) and electrical conductivity also decrease with increasing Ni content. The x = 0.2 and 0.4 samples exhibit slightly improved performance as cathodes in single cell solid oxide fuel cell (SOFC) compared to the x = 0 sample, which is in accordance with the ac-impedance data. Among the samples studied, the x = 0.4 sample exhibits a combination of low thermal expansion and high catalytic activity for the oxygen reduction reaction in SOFC.     

Synchrotron based x-ray absorption spectroscopy investigation and temperature dependent ferroelectric properties of Ni doped BaTiO3 nanostructures

In this report, the local structure geometry of BaTi_1-xNi_xO₃ (0.0 ≤ x ≤ 0.06) ceramics has been studied through synchrotron based x-ray-absorption spectroscopy, measured at the Ti K, Ba L₃ and Ni K-edges at room temperature. The x-ray absorption near edge spectroscopy (XANES) at Ti K-edge confirms the TiO₆ octahedron geometry of Ti atom due hybridization between Ti(3d)-O(2p) orbitals and signifies the non-centrosymmetric nature of BaTiO₃ samples. However, Ti–O off-center displacement (non-centrosymmetric) is disturbed under the effect of Ni doping as a result of oxygen vacancies formation. More interestingly, XANES studies at Ni K-edge ensure successful substitution of Ni in BaTiO₃ as Ni²⁺ ions. Extended x-ray absorption fine structure (EXAFS) data at Ni K-edge have been fitted to estimate pertinent local structural parameters of the Ni–O, Ni–Ba, Ni–Ti and Ni–Ni shells (viz. bond lengths and disorder parameters) and it also reveal that the structural disorders around the Ti sites in the doped BaTiO₃ expand with Ni doping. The mixed-valence states of titanium ion, i.e., Ti⁴⁺ and Ti³⁺ in the doped samples were established with the x-ray photoelectron spectroscopy (XPS). Moreover, XPS divulges the creation of oxygen vacancies due to Ni doping in BaTiO₃ matrix. The complementary information about the lattice vibration is analyzed through Raman studies that approve the softening of the transverse optical (TO) mode present at 515 cm^?1. The temperature dependent ferroelectric studies affirm that the ferroelectricity vanishes in the doped samples due to the decrement in the off-center displacement between the Ti⁴⁺ and O^2? ions in the TiO₆ octahedral geometry. Differential thermal analysis (DTA) exhibits a ferroelectric tetragonal to para-electric cubic phase transition in the pristine as well as Ni doped BaTiO₃ samples.