Cubic Phase Structure Research Articles

Comparative Study of Yttria-Stabilized Zirconia Synthesis by Co-Precipitation and Solvothermal Methods

Yttria-stabilized zirconia (YSZ) at 8 mol.% is the most commonly used electrolyte material in the solid oxide fuel cell field. In this study, co-precipitation and solvothermal methods are used to synthesize nanocrystalline yttria-stabilized zirconia. The effects of the synthesis condition (calcination temperature) and different methods on the crystal phase, the microstructure and the electrical performance of YSZ are comparatively investigated and analyzed in detail. X-ray diffraction results reveal that both the co-precipitation and solvothermal methods can be used to successfully synthesize nano-YSZ ceramic powders with a pure crystal phase of fluorite cubic structure. The grain sizes of the YSZ samples prepared by these two methods are both smaller than that of the commercial Tosoh YSZ, with the sample from the solvothermal method revealing the smallest grain size. The electrochemical impedance spectra demonstrate that the YSZ prepared by co-precipitation with 500°C calcination reveals the smallest ohmic resistance among different calcination temperatures. It also shows a relatively lower ohmic resistance of 2.04 Ω cm2, while the YSZ sample synthesized by the solvothermal method has a higher ohmic resistance of 8.89 Ω cm2, with corresponding ionic conductivities of 0.0266 S cm−1 and 0.00562 S cm−1, respectively.

The effect of the interface on magnetic properties of perovskite-spinel nanocomposites

In this research, perovskite-spinel nanocomposite with formula (x)(Cuo.3Mn0.7Fe2O4)- (1-x)(La0.9o Bi0.10 FeO3); 0 ≤ x ≤ 1, were prepared by the auto-combustion method. A single phase of orthorhombic and cubic structure for La0.9oBi0.10FeO3(LBFO); Cuo.3Mn0.7Fe2O4(CMFO) respectively have been proved for two parents and nanocomposites without any further secondary phase using XRD analysis. High-resolution transmission electron microscopy (HRTEM) images reveal nearly spherical nanoparticles for the parents and agglomerated for nanocomposites. Magnetic hysteresis loops demonstrate ferromagnetic (FM) behavior for the spinel compound and nanocomposite, where LBFO possesses G-type antiferromagnetic (AFM). Competition between FM and AFM phases lead to enhancement in magnetic parameters such as saturation magnetization (Ms), remnant magnetization (Mr) and coercivity (Hc). The magnetic properties at low temperatures show the decrease in magnetization and coercivity with increasing the temperature while the magnetic exchange bias HEB was increased until T=200 K and then decreased. The existence of intergranular magnetostatic interactions between the LBFO and CMFO interact at the interface of nanocomposites and play a decisive role in strain energy, exchange energy, and magnetic anisotropy

Study of the effect of non-thermal plasma on the structural properties of pure Cadmium Oxide thin Films (CdO) prepared by Pulsed laser Deposition Technique ( PLD )

In this research, the preparation of pure ( CdO ) films on a glass substrate were conducted using a pulsed laser deposition method (PLD) . The deposition of the films was done at different times ( 5 , 10 , 15, 20 ) minutes at room temperature. The effect of non-thermal plasma on these prepared films in two exposure times of (30, 60) minutes was studied. The results of X-ray diffraction (XRD) of the prepared pure ( CdO) films showed that the films have a polycrystalline structure of cubic phase with preferred orientation (111). It was noted that the increase of deposition time of (Nd : YAG) laser, reduces the intensity of diffraction peaks at (111 ) , (200) , (220) . The results of (XRD) have also shown that when the prepared pure ( CdO ) films are exposed to the non-thermal plasma, their crystalline structure was not affected. The tests also showed that the increase of the exposure time to non-thermal plasma causes a decrease in the intensity of the diffraction peaks. The (AFM) tests also demonstrated that the changing in ( RMS ) of the surface roughness is irregular and it was found that the ( RMS ) increases by increasing the deposition time.

Preparation and Morphology of CdZnS Thin Films

Thin films based on limited solid solutions of cadmium and zinc sulfides have been synthesized by a one-stage epitaxial layer-by-layer deposition from an ammonium-containing aqueous solution of cadmium and zinc chlorides and thiocarbamide on a glass substrate. The thickness control of sulfide layers was carried out by selection of reagent concentrations and the deposition conditions. The relationship between the synthesis conditions of CdxZn[Formula: see text]S thin films and the size of sulfide nanoparticles in these films is established. The films contain two phases: hexagonal (space group [Formula: see text]) phase with [Formula: see text] structure of wurtzite type and cubic (space group [Formula: see text]-[Formula: see text]) phase with [Formula: see text] structure of sphalerite type. It is shown that the CdxZn[Formula: see text]S film consists of separate [Formula: see text][Formula: see text]nm agglomerates which are a collection of smaller nanometer-sized particles. The dependence of the band gap of the synthesized films on their thickness is found.

Structural, Morphological, Electrical and Magnetic Properties of Yttrium-Substituted Co-Zn Ferrites Synthesized by Double Sintering Technique

A series of rare earth Y3+ ion substituted Co-Zn ferrites Co0.5Zn0.5YxFe2-xO4 (x = 0.00 to 0.08 in step of 0.02) have been synthesized by conventional double sintering technique from the oxide powders of Co, Zn, Fe, and Y. The XRD, FESEM, EDS, DC resistivity, dielectric measurements, VSM, and Curie temperature (Tc) analysis have been used to investigate structural, morphological, electrical, and magnetic properties. Single phase of cubic spinel structure has been confirmed up to x 0.06. The lattice parameter initially decreases than increases with yttrium concentrations. The FESEM image shows that the grains and grain boundaries are distinct and uniformly distributed and the purity has also been endorsed from the EDS spectra. The average grain size decreases at x = 0.02 and then increases with Y substitution. The long range mobility of charge carriers and presence of localized charge carriers with retreat from the Debye-like behavior in the compositions have been explored using electric modulus and impedance. The magnetic strength diminishes owing to existence of magnetic dilution in the A-B interactions subsequent to the Tc declines with the x contents. The value of saturation magnetization decreases with increasing Y3+ contents that indicates that the domain wall motion become tougher due to substitution of foreign ions Y3+ that possess larger ionic radius. Therefore, the Y3+ substituted Co0.5Zn0.5YxFe2-xO4 (x = 0.00 to 0.08 in step of 0.02) ferrites with high resistivity and low losses has implications to be used in high frequency and power supply devices applications.

Hexagonal Closed-Packed Precipitation Enhancement in a NbTiHfZr Refractory High-Entropy Alloy

A NbTiHfZr high-entropy alloy (HEA) with a main phase of body-centered cubic structure is fabricated. Some hexagonal closed-packed (hcp) precipitates are observed in this alloy. A thermal-mechanical process, i.e., cold-rolling followed by annealing, can manipulate the volume fraction of the hcp nano-precipitates that can enhance strength and ductility. The enhancement is tailorable as a function of the volume fraction of the hcp nano-precipitate. The results indicate that the strength-ductility property can be manipulated via adjusting post-deformation heat-treatment methods, which provide a new strategy by utilizing metastability at high-temperature to design high strength refractory HEAs (RHEAs) without lost in ductility.

Electrogenic transport of Na+/K+-ATPase incorporated in lipidic cubic phases as a model biomimetic membrane

The transmembrane pump Na+/K+-ATPase was reconstituted within a model membrane-mimetic system of monoolein liquid-crystalline cubic phase (LCP). LCP consists of a curved lipid bilayer forming the walls of a network of aqueous channels providing the lipid environment for the hydrophobic part of Na+/K+-ATPase, with the aqueous channels enabling protein contact with the aqueous environment. Electrogenic ion transport by Na+/K+-ATPase was investigated by chronoamperometry (CA). The results of the electrochemical measurements were compared with the spectroscopic assay of the protein activity. The transient currents were recorded following application of potential steps to the LCP modified electrode. Na+/K+-ATPase embedded in the lipidic part of the cubic phase transports cations across the mesophase film. Moreover, the lack of Na+ halted protein function because Na+ ions are required to promote the enzyme switching to P-E2 conformation. A specific Na+/K+-ATPase inhibitor, ouabain, added to the solution decreased ion transport abilities of the protein. Small-angle X-ray scattering (SAXS) measurements showed that the structure of cubic phase with incorporated Na+/K+-ATPase before and after the chronoamperometry experiments remained unchanged, and that the observed difference in current flowing through the cubic phase film with and without the protein was due to Na+/K+-ATPase activity in this environment.

A novel orange–red emitting phosphor Sr2LuTaO6:Sm3+ for WLEDs

A novel double perovskite tantalite orange–red light emitting Sr2LuTaO6:Sm3+ phosphor was synthesized by the solid state reaction. The phase, crystal structure, photoluminescence properties, thermal stability and decay curves were studied. The X-ray diffraction patterns indicated that the phosphor has a pure phase of cubic phase structure. Excited by near-ultraviolet light at 407 nm, the sample exhibited three sharp emission peaks at 564 nm, 600 nm, 645 nm corresponding to the 4G5/2 → 6HJ (J = 5/2, 7/2 and 9/2) transitions, respectively. The optimum doping concentration of Sm3+ ions was determined to be 5 mol% and the concentration quenching process comes from the energy transfer among nearest-neighbor ions. The as-prepared phosphors showed excellent thermal stability, the integral intensity at 423 K is about 91.10% of the initial intensity. The CIE chromaticity coordinates of Sr2LuTaO6:Sm3+ phosphors located in orange–red region. The results suggest that Sr2LuTaO6:Sm3+ phosphors have great potential application in white light-emitting diodes.

Effects of the rare earth element lanthanum on the metal-ceramic bond strength of dental casting Co-Cr alloys

Statement of problemThe metal-ceramic bond strength of dental casting Co-Cr alloys may be improved by the addition of the rare earth element lanthanum (La), but studies are lacking. PurposeThe purpose of this in vitro study was to evaluate the effects of the rare earth element La on the metal-ceramic bond strength of dental casting Co-Cr alloys. Material and methodsFour groups of specimens with different La content (0; 0.02 wt%; 0.04 wt%; 0.06 wt%) were prepared using conventional casting methods. The metal-ceramic bond strength was assessed by using the 3-point bend test. The microstructures were characterized by metallurgical microscopy, scanning electron microscopy, and X-ray diffraction analyses. The morphology and element distribution of metal-ceramic interfaces were evaluated by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. The results of bond strengths were statistically analyzed by the Tukey honest significant difference (HSD) test (α=.05). ResultsThe specimens showed typical dendritic microstructures, few defects, and island-shaped intermetallic compounds rich in Mo and Cr, mainly consisting of α-Co phase of a face-centered cubic (FCC) structure and ε-Co phase of a close-packed hexagonal (HCP) structure. As the amount of La increased, the thickness of the native oxide layer and the diffusion layer at the interface increased, and the wettability between the oxide layer and the metal matrix improved. The mean ±standard deviation values of the metal-ceramic bond strengths were 28.11 ±4.53 MPa for group 0%, 33.13 ±5.65 MPa for group 0.02%, 37.48 ±7.86 MPa for group 0.04%, and 40.70 ±5.17 MPa for group 0.06%. The statistical analysis indicated that significant differences (P<.05) were observed among all groups tested, except for group 0.04% and 0.06% (P>.05). The debonded surfaces of Co-Cr specimens showed a mixed type of adhesive and cohesive fractures. ConclusionsThe microstructures, morphologies, and compositions of oxide films were influenced by the La content, and the La addition could significantly improve the metal-ceramic bond strength of dental casting Co-Cr alloys.

Improvement of self-heating ability in AC magnetic field of MgFe2O4 powder prepared by Polymerization method

The spinel type MgFe2O4 ferrite powder having self-heating ability in an AC magnetic field was prepared by polymerization method in order to investigated the application for thermal coagulation treatment of cancer tissue. The single phase of cubic ferrite structure was obtained for all sample synthesized with different CA/MN (Citric Acid / Metal Nitrate) conditions. The heat-generation-ability was extremely improved at CA/MN=2.0 sample (ΔT = 168°C), however the heat-generation-property decreased with increase in CA/MN ratio. Hysteresis loss value also increased at CA/MN=2.0 sample, it was suggested that the heat-generation-ability of MgFe2O4 powder prepared by polymerization method was depended on hysteresis loss value.

Effect of Cation Distribution on the Structural and Magnetic Properties of Mg Substituted Nanosized Manganese Ferrites

In the present investigation, A series of Mg-Mn ferrite nanopowders with composition MgxMn[Formula: see text]Fe2O4 (with [Formula: see text], 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by the co-precipitation method. Thereafter, the obtained powders were pressed separately to form pellets, and sintered at 1250∘C for 3[Formula: see text]h at air atmosphere. Finally, the samples were characterized by X-ray Diffraction (XRD) technique, Scanning Transmission Electron Microscopy (STEM), Alternating Gradient Force Magnetometer (AGFM) and Curie temperature measuring instrument. The lattice constant and distribution of cation in the tetrahedral and octahedral sites have been deduced through XRD data analysis. The XRD pattern confirmed the existence of single phase of cubic spinel crystal structure with the lattice parameter ranging from 8.49 Å (for MnFe2O4) to 8.35 Å (for MgFe2O4). This behavior was attributed to the ionic radii. STEM micrographs exhibit that the particles are spherically shaped and agglomerated with particle size ranging 50–90[Formula: see text]nm quite consistent with particle size obtained from XRD data. The average crystallite size was 70[Formula: see text]nm. Magnetization decreases with increasing Mg concentration except for [Formula: see text], where it shows increasing trend. Curie temperature measurements exhibit increasing trend with increase in magnesium content. The variation of the saturation magnetization and Curie temperature with increasing concentration of the Mg[Formula: see text] ions can be explained on the basis of cation distribution, strengthening A–B interaction and Neel’s two sub-lattice.

Optimized nc-Si:H thin films with enhanced optoelectronic properties prepared by micro-waves PECVD used as an effective silicon surface passivation layer

In this work we investigated a novel approach to elaborate hydrogenated nanocrystalline silicon (nc-Si:H) thin films using microwave plasma enhanced chemical vapor deposition (MW-PECVD) system, used as an efficient silicon surface passivation layer. We studied the effect of the hydrogen flow rate on the structural, morphological and optical properties of nc-Si:H thin films. Obtained results confirm its crucial role on the properties of the resulted thin films. Optimized hydrogen flow rate allowed an hydrogenated nanocrystallites (nc-Si:H) with around 80% of a crystallization phase which is a high percentage compared to previous works. The XRD analysis was supported by Raman spectroscopy, indicating the pure phase of cubic structure with a preferred orientation along (111) plane. The average grain size was found to vary between 7 and 16 nm. The surface morphology of the deposited thin films was carried out using atomic force microscopy (AFM), showing a clear dependence of surface roughness with the hydrogen flow rate. The refractive index of the obtained thin films was evaluated by means of the Bruggeman effective medium approximation (BEMA). The optical band gap and the porosity of the films were deduced from spectroscopic ellipsometry measurements and results were found strongly correlated with XRD and AFM analysis respectively. Moreover, the minority carrier lifetime measurements (MCL) prove the effectiveness of the subjected treatment for a high quality nc-Si:H thin film and its crucial role as a passivation layer of crystalline silicon substrate, revealing a significant improvement of their optoelectronic properties.

Electronic energy levels and electrochemical properties of co-electrodeposited CdSe thin films

CdSe semiconductor thin films were grown on indium tin oxide (ITO) coated glass substrates by co-electrochemical deposition method. Deposition potential was kept at − 0.95 V vs. Ag/AgCl reference electrode for ten minutes. Deposition electrolyte includes an aqueous solution of 10 mM CdCl2, 20 mM H2SeO3 as precursors, 200 mM LiCl as complexing agent, and HCl for adjusting of pH. Deposited CdSe thin film was annealed at 500 °C for 30 min in air medium. Precursor and annealed CdSe thin films were characterized using a number of techniques, including SEM, EDX, XRD, UV–vis spectroscopy, and electrochemical impedance spectroscopy. SEM studies show that annealing alters the surface of precursor CdSe film from smooth to granular appearance. According to EDX analyses, the ratio of Cd/Se is close to 1.07 and 1.04 for the precursor and annealed CdSe thin film, respectively. XRD analysis shows that each film has polycrystalline structure. Precursor film has only cubic structure of CdSe, while annealed film has hexagonal structure of CdSe and cubic crystal phase of CdO. Optical energy band gap of the as-deposited CdSe film increases from 1.64 to 1.71 eV after annealing due to the mixture of the two phases. Refractive index against wavelength changes between 2.0 and 3.3. Calculations performed by using the data of Mott-Schottky measurements show that precursor CdSe film has 1.72 × 1016 cm−3, while annealed film is of 3.65 × 1017 cm−3 carrier concentration. The prepared films exhibit n-type semiconductor character. The study reports energy level diagrams of the produced semiconductor CdSe thin films by using the Mott-Schottky and Tauc's approximations. The carrier transport properties in the interface between active CdSe thin film and electrolyte are discussed based on an equivalent electronic circuit simulated to the Nyquist data of the CdSe/electrolyte system.

Influence of cobalt substitution on the properties of Ni0.95-xCoxCu0.05Fe2O4 ferrite nanoparticles

Cobalt substituted nickel copper ferrite samples with general formula Ni0.95-xCoxCu0.05Fe2O4, where (x= 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05) were prepared by solid-state reactions method at 1373 K for 4h. The samples prepared were examined by X-ray diffraction (XRD(, atomic force microscope (AFM), Fourier transform infra-red spectroscopy (FTIR) and Vickers hardness. X-ray diffraction patterns confirm the formation of a single phase of cubic spinel structure in all the prepared samples . XRD analysis showed that the increase in the cobalt concentration causes an increase in the lattice constant, bulk density (ρm) and the x-ray density (ρx), whereas porosity (p) and crystallite size (D) decrease. The Topography of the surface observed was found to be more uniform and homogeneous when the cobalt concentration increases, leading to a decrease in the roughness of the surface while average grains size increases. The FTIR spectra show two absorption bands, namely the high frequency band (υ1) in the range (1078-1081) cm-1 and the low frequency band (υ2) in the range (418–459) cm-1, which due to the vibrations of the tetrahedral and octahedral sites of Fe+3–O−2, respectively, these bands confirm the spinel structure of the prepared ferrite nanoparticles. Vickers hardness was found to increase with cobalt concentration increases.

Influence of the Conditions of the Chemical Bath Deposition of Thin ZnSe Films on Their Morphology and Internal Mechanical Stresses

ZnSe films up to 2300 nm thick on glass-ceramic supports were prepared by chemical bath deposition in the ZnCl2–Na2EDTA–NaOH–NH2OH·HCl system using sodium selenosulfate as a chalcogenizer. The reflections observed in the X-ray diffraction patterns correspond to the ZnSe (stilleite) phase of cubic (space group F $$\overline 4 $$ 3m) structure with a = 5.610 ± 0.002 A. As shown by electron-microscopic examination, ZnSe films consist of globular formations tightly adjoining to each other with the mean size of 250–400 nm depending on the deposition conditions. Elemental EDX analysis shows that the films contain, on the average, 43.68 at. % Zn, 30.50 at. % Se, and 25.82 at. % O, with the oxygen concentration somewhat decreasing at a depth of 30 nm. The internal mechanical compression stresses caused by the difference in the thermal expansion coefficients of the ZnSe film and glass-ceramic support were calculated; these stresses depend on the film thickness and at ~1040 nm reach–30.62 kN m–2. The results obtained make it possible to exclude film discontinuities, which can appear with increasing film thickness in preparation of precursor layers, and to choose the optimum support material.

The Effects of Mo and Nb on the Microstructures and Properties of CrFeCoNi(Nb,Mo) Alloys.

The effects of niobium and molybdenum additions on the microstructures, hardness and corrosion behaviors of CrFeCoNi(Nb,Mo) alloys were investigated. All of the CrFeCoNi(Nb,Mo) alloys displayed dendritic microstructures. The dendrites of CrFeCoNiNb and CrFeCoNiNb0.5Mo0.5 alloys were a hexagonal close packing (HCP) phase and the interdendrites were a eutectic structure of HCP and face-centered cubic (FCC) phases. Additionally, the dendrites of CrFeCoNiMo alloys were a simple cubic (SC) phase and the interdendrites were a eutectic structure of SC and FCC phases. The volume fraction of dendrites and interdendrites in these alloys were calculated. The influences of the volume fraction of dendrite in the alloys on the overall hardness were also discussed. The CrFeCoNiNb alloy had the larger volume fraction of dendrite and thus had the highest hardness among these alloys. The CrFeCoNi(Nb,Mo) alloys also showed better corrosion resistances in 1 M H2SO4 and 1 M NaCl solutions by comparing with commercial 304 stainless steel. The CrFeCoNiNb0.5Mo0.5 alloy possessed the best corrosion resistances in these solutions among the CrFeCoNi(Nb,Mo) alloys.

Preparation of Cr3+-Substituted NiFe2O4 Nanoparticles and Its Microwave Absorption Properties

In the present work, spinel Ni(1−X)CrXFe2O4 (X = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 M) nanoparticles were synthesized by co-precipitation method followed by calcination at 400 °C for 2 h. The structural and morphological properties of the synthesized nanoparticles were studied using powder XRD,micro-Raman measurements, FE-SEM, TEM and EDS. The results revealed that the synthesized nanoparticles were single-crystal, cubic-phase structure with spherical shape. Energy-dispersive X-ray spectroscopy confirmed the elements present in the synthesized nanoparticles. Moreover, microwave absorption properties were measured using vector network analyser (VNA). The minimum reflection loss − 14.44 dB at 9.49 GHz was observed for Ni(1−X)CrXFe2O4 (X = 0.5 M) nanoparticles at 3 mm thickness. These results suggest that Ni(1−X)CrXFe2O4 (X = 0.5 M) nanoparticles would be applicable for microwave absorption application.

Enhancing the densification of ceria ceramic at low temperature via the cold sintering assisted two-step sintering process

The cold sintering process (CSP) in the transient aqueous environment of malonic acid is applied in this study to enhance the densification behavior of ceria ceramics at a significantly reduced sintering temperature. Dense ceria ceramics (> 98% relative density) could be achieved after CSP at 180 °C, followed by the sintering at 1100 °C/4 h. As expected, the CSP can improve the compaction of the particles before sintering, resulting in ceria ceramics with a fine microstructure of submicrometer scale of grain sizes. All samples show the single phase of cubic fluorite structure with no significant change of lattice parameter. Finally, electrical conductivity of CSP and conventionally sintered ceramics is investigated. This communication emphasizes the advantage of the CSP to reduce the sintering temperature without deterioration of the structure and properties of the final ceramics.

Incident photon-to-current efficiency of thermally treated SWCNTs-based nanocomposite for dye-sensitized solar cell

This study focuses on incident photon-to-current efficiency (IPCE) performance of In2O3-SWCNTs for dye-sensitized solar cell (DSSC) application. The thin films were prepared by sol-gel method using spin-coating technique annealed at 400, 450, 500, 550, and 600 °C. Morphology transition of In2O3 from spherical to cubic and then octahedral structure occurred as the annealing temperature rises. The photoanode annealed at 450 °C (cubic structure) provides a stable phase of cubic structure with large surface area and optimum thickness for effective dye adsorption. However, the IPCE value does not solely depends on the dye adsorption of photoanodes (light harvesting efficiency (LHE)) but the electron injection efficiency (ηinj) and the collection efficiency (ηcoll). Smaller energy bandgap of photoanodes favors the injected electrons with higher driving force to the conduction band (CB) of the photoanode, which in turn increases the ηinj from the LUMO of dye to the In2O3-SWCNTs CB. Besides that, the absence of single-walled carbon nanotubes (SWCNTs) above 500 °C caused the energy bandgap to increase and leads to lower driving force of injected electrons. In addition, SWCNTs are capable of absorbing visible light faster than other materials. Therefore, the cubic structure-based photoanode (450 °C) exhibited better electron transport with larger driving force on injected electron (ηinj) that decreased the electron recombination rate and increased electron lifetime and subsequently obtained larger charge collection efficiency (ηcoll) of almost 99%. Consequently, the IPCE performance of DSSC was enhanced.

Electronic Structure of Visible Light-Driven Photocatalyst δ-Bi11VO19 Nanoparticles Synthesized by Thermal Plasma.

Size confinement for tailoring of electronic structures can in principle be explored for enhancement of photocatalytic properties. In the present work, vanadium-doped bismuth oxide nanoparticles, with an average particle size of 36 nm, are synthesized for the first time, using the thermal plasma method, in large scale with high yield to explore for photocatalytic applications. The electronic and crystallographic structures of the sample are studied experimentally and theoretically. Systematic investigations of the electronic structure of the fluorite type cubic phase of Bi11VO19 nanoparticles are reported for the first time. Enhancement is observed in the photocatalytic activity as compared to other delta phases of bismuth vanadate. The valence band is found to comprise mainly of O 2p states, whereas the conduction band arises from V 3d states giving rise to a band gap value of 2.26 eV. Absence of excess O in δ-Bi2O3 results in shrinking of the band gap because of O 2p, Bi 6s and 6p states from the surrounding atoms at doping sites. Bi11VO19 nanoparticles show an efficient visible light absorption and exhibit excellent photodegradation properties of methylene blue solution under visible light irradiation.