Doped Zirconia Research Articles

Effect of variable trivalent europium concentration on photo- and thermoluminescence of zirconium dioxide nanophosphors

The present paper reports synthesis and characterization of trivalent europium (Eu3+) doped zirconium dioxide (ZrO2) nanophosphors. Effect of variable concentrations of europium on photoluminescence (PL) and thermoluminescence (TL) behavior is also studied. Samples were prepared by the combustion synthesis technique which is suitable for less time taking techniques and also for large scale production of nanophosphors. Starting materials used for sample preparation are Zr(NO3)3 and Eu(NO3)3 and urea is used as a fuel. The prepared sample was characterized by an X-ray diffraction technique (XRD) with variable concentrations of Eu3+ (0.5–2.5mol%). There was no phase change found with increase in the concentration of Eu3+. Sample shows monoclinic structure and the crystallite sizes were calculated by Scherer׳s formula. The surface morphology of prepared phosphor was determined by a field emission gun scanning electron microscopy technique. Good connectivity with grains and the sphere line structure was found by FEGSEM. Functional group analysis was determined by Fourier transform infrared spectroscopic techniques. All prepared phosphors with variable concentrations of Eu3+ (0.5–2.5mol%) were studied by photoluminescence analysis and it was found that the excitation spectra of prepared phosphor showed sharp excitation peak centered at 295nm. The emission spectra with variable concentrations of Eu3+ show strong peaks at 594nm and 612nm range with dominant peak at 612nm due to the allowed electronic transition 5D0→7F2 and weaker transition at 594nm which was due to magnetic dipole transition 5D0→7F1. Spectrophotometric determinations of peaks are evaluated by the Commission Internationale de I׳Eclairage technique. The prepared phosphor was also examined by the thermoluminescence technique. For recording TL glow curve, every time 2mg phosphor was irradiated by UV 254nm source, with a fixed heating rate at 6.7°Cs−1. Sample showed well resolved peak at 170°C for 2mol% of Eu3+. Also the effect of Eu3+ concentration at fixed UV exposure time was studied. Effect of UV exposure time and dose versus intensity plot were studied. The sample shows linear response with dose and broaden peak with high temperature shows more stability and less fading in TL glow curve. The linear dose response, high stability and less fading phenomenon show that the sample may be useful for thermoluminescence dosimetry application. Trapping parameters were also calculated for each recorded glow curve.

Ferric-manganese doped sulphated zirconia nanoparticles catalyst for single-step biodiesel production from waste cooking oil: Characterization and optimization

ABSTRACTBiodiesel of waste cooking oil origin is gaining attention as a replacement for current fossil fuels, as its low-priced, recycled feedstock shall prevent food source competition, which is estimated to happen with current biodiesel production processes. As a result, waste cooking oil has been claimed to be a highly potential feedstock for biodiesel production. In the present research work, Fe-Mn doped sulphated zirconia catalyst was synthesized and used in simultaneous esterification and transesterification of waste cooking oil to biodiesel synthesis. The catalyst was prepared through the impregnation method and characterized by using XRD, TPD-NH3, FT-IR, BET, and TEM. Response surface methodology (RSM) in conjunction with the central composite design (CCD) was applied to statistically evaluate and optimize the biodiesel preparation process. It was found that the synthesis of biodiesel achieved an optimum level of 97.2% waste cooking oil methyl ester’s (WCOME’s) yield at the following reaction conditions: methanol/oil molar ratio: 10:1, catalyst concentration: 3.0 wt %, and reaction temperature: 160 °C. The extremely high WCOME’s yield of 97.2% was proved to be due to high acidity, surface area, and large pore diameter; reactants can easily diffuse into the interior pore of the catalyst and allow them to be in contact with active sites that enhance catalytic activity.

Nanostructured crystals of partially yttria-stabilized and Nd3+ doped zirconia: Structure and luminescent properties

The structure and luminescent characteristics of partially yttria-stabilized zirconia (PSZ) doped with Nd3+ ions were investigated. Transmission electron microscopy (TEM) data for PSZ crystals containing 2.8mol.% and 3.7mol.% Y2O3 doped with Nd2O3 (0.04, 0.22 and 0.34mol.%) and containing 2.0mol.% Y2O3 doped with 0.8mol.% Nd2O3 indicated the presence of a nanosize twin domain structure. This structure becomes more homogeneous and dispersed as the total concentrations of the stabilizing oxides (Y2O3 and Nd2O3) increases.A comparison of the luminescence spectra and X-ray phase analysis results for the PSZ crystals containing 2.8 and 3.7mol.% Y2O3 with different Nd2O3 concentrations (0.04, 0.22 and 0.34mol.%) indicated that the Nd3+ ions were predominantly concentrated in the non-transformable t′ phase. The luminescence spectra of Nd3+ centres in these crystals were similar to those of yttrium-stabilized cubic zirconia. In the 0.8Nd2O3–2.0YSZ crystal the quantity of the non-transformable t′ phase is low, therefore the Nd3+ ions are contained in the transformable t phase. The luminescence spectra of Nd3+ ions occupying transformable t phase in 0.8Nd2O3–2.0YSZ crystal differs from the luminescence spectra of Nd3+ ions in stabilized cubic zirconia.

Lithium zirconate as solid catalyst for simultaneous esterification and transesterification of low quality triglycerides

Alkali metal (Li, Na and K) doped zirconium oxide was prepared (Li/ZrO2, Na/ZrO2 and K/ZrO2) by wet chemical route and used as active heterogeneous catalyst for the transesterification of waste cottonseed oil with ethanol and methanol to produce fatty acid ethyl and methyl esters, respectively. The catalyst characterization supports the formation of lithium zirconate single phase in the case of Li/ZrO2 and it was able to catalyze simultaneous esterification and transesterification of high free fatty acid containing vegetable oils (VOs). The reaction conditions, such as catalyst concentration, reaction temperature, the molar ratio of alcohol/oil and stirring speed, were optimized in the presence of Li/ZrO2 catalyst. The catalyst activity was found to be a function of its basic sites which in turn depends on calcination temperature and lithium content of the catalyst. A pseudo first order kinetic equation was applied to evaluate the kinetic parameters for the transesterification of waste cottonseed oil with methanol and ethanol. The activation energy (Ea) for the Li/ZrO2 catalyzed methanolysis and ethanolysis was found to be 40.8 and 43.1kJmol−1, respectively. The catalyst could be reused up to nine cycles without significant loss of performance as >90% fatty acid alkyl ester yield was maintained.

Near-infrared light emission of Er3+-doped zirconium oxide thin films: An optical, structural and XPS study

This paper investigates the near-infrared emission and structural properties of Er3+-doped zirconium oxide thin films modified with a fixed content of zinc oxide. The films were obtained by electron beam deposition on Si(100) substrates, followed by a thermal treatment with or without a controlled oxygen flow. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX). Scanning electron microscopy (SEM) was used to evaluate the surface morphology, distributions and size of the grains in the films. The results confirmed significant changes in these films from thermal treatment with or without oxygen flow. Fourier transform infrared spectroscopy (FTIR) was used to analyze the absorption bands of the films. The photoluminescence (PL) measurement and 4I13/2→4I15/2 lifetime was measured under 980nm near-infrared excitation. The effects of thermal treatment as well as the concentration of Er2O3 on the PL emission intensity and lifetime in the near-infrared region (from the 4I13/2→4I15/2 radiative transition) were studied. Thermal treatment under a controlled atmosphere increased the PL emission intensity due to a diminution of the residual OH groups, as confirmed by the XPS and analysis and FTIR spectroscopy. The film modified with 3mol% of Er2O3 content annealed in oxygen flow shows an emission intensity of two orders of magnitude greater than the annealed film without oxygen flow at 1550nm, nevertheless, the bandwidth was practically the same (7.6nm) in both cases.

Magnetic Properties of Fe<sub>3</sub>O<sub>4</sub> Stabilized Zirconia

Doping effects of acidic (pH4) and basic (pH10) Fe 3 O 4 on the magnetic properties of ZrO 2 have been reported in this paper. Fe 3 O 4 doped zirconia (FZ) sol is synthesized by varying Fe 3 O 4 concentrations in the range of 2-10 wt% using sol-gel route. FZ sols are spin coated onto glass substrates and then vacuum annealed at 300 °C for 60 min in the presence of 500 Oe magnetic field. X-ray diffraction results show amorphous behavior at 2 wt% doping in both acidic and basic cases. Mixed monoclinic-tetragonal behavior is observed in acidic films with 6-10 wt% doping concentration. However, tetragonal phase is observed in basic films with 8-10 wt% doping. Soft ferromagnetic behavior is observed in both the acidic and basic doped zirconia. Saturation magnetization (M s ) of ~33 emu/g is observed in acidic FZ samples whereas, variation in M s (1-36 emu/g) is observed in basic FZ samples. Iron oxide stabilized ZrO 2 , with soft ferromagnetic behavior, can be employed for coatings on teeth as well as for diagnosis and therapy of oral cancer.

Single-longitudinal-mode operation in tunable novel zirconia–yttria–alumina–erbium-doped fiber laser

A tunable, single-longitudinal-mode (SLM) fiber laser based on a short length, highly doped zirconia–erbium doped fiber (Zr-EDF) is proposed and demonstrated. The Zr-EDF is a novel fiber with an erbium ion concentration of 4320 ppm wt − 1 and an absorption rate of approximately 22.0 dB m − 1 at 978 nm, while at the same time being highly compatible with conventional silica-based optical fibers. The Zr-EDF is used as the gain medium in the laser cavity, while a tunable C-band fiber Bragg grating is used to adjust the operating wavelength of the system, providing an operating wavelength range of between 1533.8 nm to 1545.0 nm. Two short erbium-doped fibers, with active ion concentrations of 900 ppm wt − 1, serve as saturable absorbers, and allow for an SLM output with a narrow laser linewidth of only 0.2 MHz. The proposed system has multiple applications as a tunable SLM laser for communications and sensing purposes.

The role of Nb in intensity increase of Er ion upconversion luminescence in zirconia

It is found that Nb co-doping increases the luminescence and upconversion luminescence intensity in rare earth doped zirconia. Er and Yb-doped nanocrystalline samples with or without Nb co-doping were prepared by sol-gel method and thermally annealed to check for the impact of phase transition on luminescence properties. Phase composition and grain sizes were examined by X-ray diffraction; the morphology was checked by scanning- and high-resolution transmission electron microscopes. Both steady-state and time-resolved luminescence were studied. Comparison of samples with different oxygen vacancy concentrations and different Nb concentrations confirmed the known assumption that oxygen vacancies are the main agents for tetragonal or cubic phase stabilization. The oxygen vacancies quench the upconversion luminescence; however, they also prevent agglomeration of rare-earth ions and/or displacement of rare-earth ions to grain surfaces. It is found that co-doping with Nb ions significantly (>20 times) increases upconversion luminescence intensity. Hence, ZrO2:Er:Yb:Nb nanocrystals may show promise for upconversion applications.

Influence of Zr4+ doping on structural, spectroscopic and conductivity studies of lithium titanium phosphate

Zirconium doped LiTi2(PO4)3 (LTP) samples with the chemical composition of Li[Ti2−xZrx](PO4)3 (x=0.0, 0.1, 0.3 and 0.5) are prepared by solid state reaction method. XRD data revealed the formation of phase pure materials of rhombohedral structure with space group R3¯c(#167). Microstructural studies by scanning electron microscopy indicated that the particle size is in the range of 0.5–1μm. Raman spectroscopic study showed that the peaks at high frequencies are due to intramolecular PO43− stretching modes. Electrochemical impedance studies showed high ionic conductivity for small amount of Zirconium (x=0.1) doping.

Effect of Doping on Electrical and Optical Properties of Zirconium Doped and Undoped Titanium Dioxide Nanoparticle

Effect of Doping on Electrical and Optical Properties of Zirconium Doped and Undoped Titanium Dioxide Nanoparticle

Synthesis and cathodoluminescence characterization of ZrO2:Er3+ films

Trivalent erbium doped zirconium oxide films were deposited by the ultrasonic spray pyrolysis technique. Films were deposited using zirconium tetrachloride octahydrate (ZrCl4O·8H2O) and erbium nitrate hexahydrate ((NO3)3Er·6H2O) as precursors and deionized water as solvent. The dopant concentrations in the spray solution were 1, 3, 5, 10 and 15at% in ratio to zirconium content. The films were deposited on corning glass substrates at different temperatures from 400 up to 550°C. Films deposited at temperatures lower than 400°C were amorphous, however, as substrate temperatures are increased, the ZrO2 films presented a better crystallinity and showed a tetragonal phase. Cathodoluminescence (CL) emission spectra showed bands centred at 524, 544 and 655nm associated with the electronic transition of Er3+.

Synthesis of Ferric–Manganese Doped Tungstated Zirconia Nanoparticles as Heterogeneous Solid Superacid Catalyst for Biodiesel Production From Waste Cooking Oil

The solid superacid catalyst ferric-manganese doped tungstated zirconia (FMWZ) nanoparticles was prepared by impregnation reaction followed by calcination at 600°C for 3 hr and had been characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), temperature programmed desorption of NH3 (TPD-NH3), X-ray fluorescence (XRF), transmission electron microscopy (TEM), and Brunner-Emmett-Teller (BET) surface area measurement. The transesterification reaction was used to determine the optimum conditions of methanolysis of waste cooking oil with FMWZ nanoparticles as heterogeneous solid superacid catalyst. The reactions variables such as reaction temperatures, catalyst loading, molar ratio of methanol/oil and reusability were also assessed which effects the waste cooking oil methyl esters (WCOME’s) production yield. The catalyst was reused ten times without any loss in activity and maximum yield of 96% was achieved at the optimized conditions of reaction temperature of 200°C; stirring speed of 600 rpm, 1:25 molar ratio of oil to alcohol and 4% w/w catalyst loading. The fuel properties of the WCOME’s were discussed in light of ASTM D6751 biodiesel standard.

Microstructure and thermal properties of inflight rare-earth doped thermal barriers prepared by suspension plasma spray

Rare-earth doped yttria-stabilized zirconia (YSZ) coatings with lower thermal conductivity have been fabricated via suspension plasma spray by dissolving rare-earth nitrates into YSZ powder-ethanol suspensions prior to plasma spraying. The effect of dopant concentration and dopant type on properties of the coatings was determined by comparing two coatings containing different concentrations of the same dopant pair (Nd 2 O 3 /Yb 2 O 3 ), and three coatings having similar concentrations of different dopant pairs (Nd 2 O 3 /Yb 2 O 3 , Nd 2 O 3 /Gd 2 O 3 , and Gd 2 O 3 /Yb 2 O 3 ). The porosity content of the coating was found to increase with increased total rare-earth dopant concentration but did not significantly change with dopant pairs. The cross-sectional morphology of every coating displayed a cauliflower-like structure. However, the most heavily doped coating exhibited a larger surface roughness and feathery features in the columnar structures. The thermal conductivity measurement showed that the thermal conductivity decreased with increased Nd 2 O 3 /Yb 2 O 3 concentration. Among coatings containing different dopant pairs, the Gd 2 O 3 /Yb 2 O 3 doped coating exhibited lowest conductivity.

Photoluminescence properties of Eu3+ in garnet-type Li7La3Zr2O12 polycrystalline ceramics

Abstract Novel Eu 3+ doped zirconate garnet-type ceramics, Li 7 (La 3− x Eu x )Zr 2 O 12 with x =0, 0.001–1.0, have been synthesized by solid state reaction and the purity phase of the samples was checked by XRD. Room temperature steady and time-resolved emission spectra, under UV and visible light excitation energy, have been investigated. The concentration effect on the quenching blue emission, due to the Zr–O charge transfer transition and 5 D 0 → 7 F 2 emission transition of Eu 3+ were studied in detail. The results indicate that there exists efficient energy transfer from host to Eu 3+ . The mechanism of interaction between Eu 3+ ions has also been investigated by means of the Inokuti–Hirayama model.

Functionalized PLGA-doped zirconium oxide ceramics for bone tissue regeneration

Bone tissue engineering is an alternative approach to bone grafts. In our study we aim to develop a composite scaffold for bone regeneration made of doped zirconium oxide (ZrO2) conjugated with poly(lactic-co-glycolic acid) (PLGA) particles for the delivery of growth factors. In this composite, the PLGA microspheres are designed to release a crucial growth factor for bone formation, bone morphogenetic protein-2 (BMP2). We found that by changing the polymer's molecular weight and composition, we could control microsphere loading, release and size. The BMP2 released from PLGA microspheres retained its biological activity and increased osteoblastic marker expression in human mesenchymal stem cells (hMSCs). Uncapped PLGA microspheres were conjugated to ZrO2 scaffolds using carbodiimide chemistry, and the composite scaffold was shown to support hMSCs growth. We also demonstrated that human umbilical vein endothelial cells (HUVECs) can be co-cultured with hMSCs on the ZrO2 scaffold for future vascularization of the scaffold. The ZrO2 composite scaffold could serve as a bone substitute for bone grafting applications with the added ability of releasing different growth factors needed for bone regeneration.

Effects of zirconium doping on the characteristics of tin oxide thin film transistors

Thin-film transistors (TFTs) with zirconium-doped tin oxide (ZSO) channels were fabricated by co-sputtering Sn and Zr metal targets. The effect of Zr on the performance of SnOx-based TFTs was studied. TFTs with an intrinsic SnOx channel did not show promising performance. However, ZSO TFTs exhibited improved electrical properties, with increased ION/IOFF and decreased subthreshold swing. The influence of zirconium doping on bias stability in tin oxide TFTs was also investigated. ZSO TFTs exhibited turn-on voltage (VON) shifts of +9V for positive stress bias, compared with +18V for intrinsic SnOx TFTs. The improvements in device performance and stability were attributed to reduced carrier concentration induced by carrier trapping at Zr impurity sites.

Zirconium Doped Titania: Destruction of Warfare Agents and Photocatalytic Degradation of Orange 2 Dye

Zirconium Doped Titania: Destruction of Warfare Agents and Photocatalytic Degradation of Orange 2 Dye

Effect of doping with refractory rare-earth metals on the structure and properties of Al–5Zn–3Mg alloys produced by powder metallurgy and casting methods

The effect of doping with transition refractory metals on the structure and properties of Al–Zn–Mg alloys produced by different methods is studied. It is ascertained that the strength of cast alloys is increased by scandium and zirconium doping due to the modifying action of scandium that arrests recrystallization and precipitation of the fine-grained phase matrix-coherent Al3(Sc1–x Zr x ) phase; the strength of alloys obtained by powder metallurgy (P/M) methods increases to a smaller extent, in which the ultrahigh cooling rate of melt atomized by high-pressure water plays the basic role in forming the fine-grained structure. The strength of powder metallurgy alloys based on wateratomized powders is substantially higher than that of similar alloys produced by the conventional casting method (standard commercial cast alloys and alloys produced by granular technology). The advantages of P/M alloys over cast alloys are especially prominent in the absence of scandium doping. The highest strength of the P/M alloys with scandium (σb = 651 MPa and σ0.2 = 596 MPa) is shown by Al–5Zn–3Mg–0.5Mn–0.7Zr–0.3Sc. Among the P/M alloys without scandium, the highest strength is shown by Al–5Zn–3Mg–0.85Zr–0.22Cr–0.17Ni–0.15Ti alloy (σb = 618 MPa and σ0.2 = = 553 MPa).

Sol–gel synthesis and photocatalytic activity of B and Zr co-doped TiO2

Effects of boron (B) and/or zirconium (Zr) doping on photocatalytic activity of sol–gel derived titania (TiO2) powders were investigated. A conventional, non-hydrous sol–gel technique was applied to synthesize the B, Zr doped/co-doped TiO2 powders. Doping was made at molar ratios of Ti/B=1 and Ti/Zr=10. Sol–gel derived xero-gels were calcined at 500°C for 3h. The crystal chemistry and the morphology of the undoped and B, Zr doped/co-doped TiO2 nanoparticles were investigated using X-ray diffractometer and scanning electron microscope. Nano-scale (9–46nm) TiO2 crystallites were obtained after calcination. Doping and co-doping decreased the crystallite size. Photocatalytic activity was measured through the degradation of methylene blue (MB) under 1h UV-irradiation using a UV–vis spectrophotometer. Results revealed that B doping into anatase caused the formation of oxygen vacancies, whereas Zr addition caused Ti substitution. Both B and Zr ions had a profound effect on the particle morphology and photocatalytic activity of TiO2. The photocatalytic activity of B and Zr doped TiO2 particles increased from 27% to 77% and 57%, respectively. The best activity (88.5%) was achieved by co-doping.

Promoting effect of zirconium doping on Mn/ZSM-5 for the selective catalytic reduction of NO with NH3

Manganese–zirconium catalysts loaded on ZSM-5 (Si/Al=25) were prepared using an ion-exchange method and investigated for the selective catalytic reduction of NO, with the aim of studying the effects of zirconium doping on the performance of Mn-based ZSM-5 catalysts. A series of characterization techniques, namely N2-sorption, X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), temperature-programmed reduction by hydrogen, and X-ray photoelectron spectroscopy (XPS), were used to characterize these samples. TEM and XRD results showed that the addition of zirconium increased the manganese dispersion and prevented manganese crystallization. XPS results demonstrated that the introduction of zirconium enhanced the manganese species enrichment on the ZSM-5 grain surfaces. After zirconium addition, some of the manganese ions were incorporated into the zirconia lattice. The strong interaction between Mn and Zr contributed to the formation of Zr3+ ions or oxygen vacancies around the Zr4+ ions, which enhanced the redox abilities of the Mn–Zr/ZSM-5 catalysts. The temperature range for efficient NO conversion was lowered after zirconium doping. The MnZr3/ZSM-5 (Mn 3.2wt.% and Zr 8.6wt.%) sample exhibited NOx conversions (>90%) over a wide temperature range (230–415°C) and markedly superior to that of Mn/ZSM-5 (296–425°C). Moreover, the formation of N2O was suppressed at low temperatures due to the presence of zirconium in the catalysts.