Doped Zirconia Research Articles

Structure evolution, thermal properties and sintering resistance of promising thermal barrier coating material La2(Zr0.75Ce0.25)2O7

Rare-earth doped zirconates are promising candidate materials for high-performance thermal barrier coatings (TBCs). The phase and microstructure stability is an important issue for the materials that must be clarified, which is related to the long-term stable work of TBCs at high temperatures. In this work, La2(Zr0.75Ce0.25)2O7 (LCZ) ceramic coatings prepared by atmospheric plasma spraying present a metastable fluorite phase, which can transform into stable pyrochlore under high-temperature annealing. The detailed structure evolution of the ceramic coatings is characterized systematically by SEM, XRD and Raman. The associated thermal properties of LCZ ceramics were also reported. Results show that LCZ ceramic has an ultralow thermal conductivity (0.65 W/m·K, 1200 °C), which is only 1/3 of that of yttria-stabilized zirconia (YSZ). The thermal expansion coefficients of LCZ ceramic increase from 9.68 × 10-6 K-1 to 10.7 × 10-6 K-1 (300 - 1500 °C), which are relatively larger than those of La2Zr2O7. Besides, Long-term sintering demonstrates that LCZ ceramic coating has preferable sintering resistance at 1500 °C, which is desirable for TBC applications.

Tailoring structural and optical properties of ZrO2 with nickel doping

Pure and nickel doped zirconium oxide (ZrO2) samples namely N1, N2, N3, N4 have been synthesized by sol–gel method at different doping concentrations (0, 1, 3 and 5 molar percentage respectively). Energy dispersive X-ray spectroscopy (EDS) was used to confirm the elemental composition of samples. X-ray diffraction data following Rietveld refinement revealed the stabilization of tetragonal phase with some impurity of monoclinic phase. Unit cell volume and tetragonality (c/a) ratio was found to be in good agreement with standard values. Results showed the increase in unit cell volume with the decrease in crystallite size. UV–visible spectroscopy, revealed the variation in optical band gap with increase in Ni dopant in ZrO2 nano-crystals due to combined effect of quantum confinement and generation of interstitial sites.

Photocatalytic degradation of an organic dye using Ag doped ZrO2 nanoparticles: Milk powder facilitated eco-friendly synthesis

Silver doped zirconium oxide nanoparticles were synthesized using milk powder via single step solution combustion method and has been examined for the removal of toxic chemicals from an organic dye. Ag doped ZrO2 were intended to play a vital role in the removal of accumulated contaminants in aqueous environment due to high efficiency of visible light triggered photocatalytic activity. The obtained product was analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV–Vis spectroscopy, BET measurements and Scanning electron microscopy (SEM). XRD and FTIR investigation probe the occurrence of silver in the synthesized final nanoparticles. The calculated average crystallite size is about 10–16 nm. Pure ZrO2 and Ag doped ZrO2 nanoparticles were analyzed against Rhodamine B (Rh B), a cataionic dye in visible light irradiation. By the analysis of experiments, silver (6 mol %) doped ZrO2 shows good photocatalyst towards 95% of Rhodamine B degradation with 150 mg photocatalyst and 10 ppm dye within 105 min.

Fabrication and characterization of rare earth (Ce, Gd, and Y) doped ZrO2 based metal-insulator-semiconductor (MIS) type Schottky barrier diodes

The 8 wt% rare earth (RE = Ce, Gd, and Y) doped zirconium dioxide (ZrO2) thin films were prepared on glass substrates by spin-coating technique and annealed at 600 °C. Also, the RE:ZrO2 based metal-insulator-semiconductor (MIS) type Schottky barrier diodes were fabricated. X-ray diffraction (XRD) patterns revealed the mixed phase of monoclinic and tetragonal ZrO2 for the RE:ZrO2 films, and the pure monoclinic phase for the undoped ZrO2 film. Because of the doping with RE ions, the crystallite size reduced with the increase of oxygen vacancies. The scanning electron microscopic (SEM) images exhibited the rod-shaped and square-shaped grains for the undoped ZrO2 and Gd:ZrO2 thin films, respectively. Elemental compositions were confirmed by the energy dispersive X-ray (EDX) analysis. The UV–vis analysis showed the lower transmittance for the RE:ZrO2 films with a reduced band gap (Eg). The dc electrical conductivity (σdc) was increased with the decrease of activation energy (Ea) due to the RE doping. When compared to the Al/undoped ZrO2/p-Si Schottky barrier diode, the Al/RE:ZrO2/p-Si showed an improvement in the values of barrier height (ΦB), ideality factor (n), and series resistance (RS).

Unexpected trends in the enhanced Ce3+ surface concentration in ceria–zirconia catalyst materials

Zirconium doping has a dramatically different influence on Ce reduction in the bulk than on the surface of ceria–zirconia.

TiO2 Co-doped with Zr and Ag shows highly efficient visible light photocatalytic behavior suitable for treatment of polluted water.

The objective of this study is to analyze the effects of zirconium (Zr) and silver (Ag) doping on the photoactivity of titania (TiO2). Zr–Ag (ZA) co-doped TiO2 products were fabricated via sol–gel technique and their properties (structural and chemical) were characterized. The weight ratio of TiO2 was fixed, while weight ratios of Zr and Ag were varied from 2 to 4, 6 and 8 wt% while synthesized samples were calcined at 400 °C for 3 h. The XRD results demonstrated that the incorporation of metal doping agents failed to alter the host material's lattice structure, however, its crystallite size was reduced from 13.54 to 5.05 nm with increasing Zr4+ and Ag+ concentrations. FTIR spectroscopy was used to examine various functional groups. In the attained spectra, an ample absorption peak between 500 and 1000 cm−1 was recorded, which was ascribed to Ti–O–Ti linkage vibration mode present within TiO2. Surface morphology, microstructure, SAED patterns and elemental composition were examined with FE-SEM, HR-TEM and EDX, which served to confirm the ZA-doped TiO2 product. Band gap energy of the co-doped material was significantly reduced as indicated by a higher wavelength redshift in the spectra. The photoactivity and kinetics of photo-products were investigated by observing photo-decolorization of methylene blue (MB) under a radiation source. Photodecomposition of MB was dramatically enhanced when titania co-doped with Zr and Ag was employed compared to un-doped or mono-doped TiO2. The ZA (8 wt%) co-doped TiO2 photocatalyst depicted the maximum MB removal efficiency (∼93%) within 90 min under a light source.

Impact of lanthanum doped zirconium oxide (LaZrO2) gate dielectric material on FinFET inverter

Abstract Fin-typed field effect transistor (FinFET) has considered a suitable device for low power and high-performance applications. The incorporation of gate dielectric lanthanum doped zirconium oxide (LaZrO2) in the 14 nm silicon on insulator (SOI) FinFET not only enhanced effective carrier mobility but also diminished the short channel effects (SCEs). The FinFET embodiment with LaZrO2 has dwindled subthreshold swing (SS), reduced drain-induced barrier lowering (DIBL), and raised on-current to off-current ratio as a contrast to SiO2-based FinFET. A remarkable enhancement of 1.18×, 11×, and 1.3× for transconductance (g m ), early voltage (V EA ), and an intrinsic gain (A V ), respectively, have been investigated. Further, LaZrO2-based n-FinFET and p-FinFET devices have devised with equal dimensions. The improved noise margin of 0.375 V using a single-fin FinFET-based inverter circuit has proven the acceptance of this device in a circuit application.

Unraveling the effect of ZrO2 modifiers on the nature of active sites on AuRu/ZrO2 catalysts for furfural hydrogenation

Ru and AuRu nanoparticles were prepared by a sol-immobilization methodology and deposited on different doped zirconia supports (ZrO2, Y–ZrO2 and La–ZrO2).

Zirconium doping level modulation combined with chalconylthiourea organic frameworks induced enhancement of luminescence applied to cell imaging

Derivatives of a zirconium metal–organic framework as the center polymer material with a chalconylthiourea polymer (CT) were applied to cell imaging.

Study of optical behaviour of Eu3+ and Tb3+ doped zirconate perovskite phosphors prepared by molten salt technique

This paper gives a keen insight of the study of spectroscopic and optical behavior of Eu3+ and Tb3+ doped calcium zirconate, barium zirconate and strontium zirconate perovskite phosphors synthesized by molten salt synthesis (MSS) technique. Here, the low temperature MSS technique uses molten chloride salt sodium chloride NaCl that increases solid–solid diffusion rate for creating an active reaction medium. These phosphors were subjected to sintering at a temperature of 950 °C with Eu3+ and Tb3+ ions doping concentration varying from 0 to 2 mol%. The Powder X-ray diffractometry technique was used to study of crystallographic behavior of synthesized phosphors. In order to study the morphological and topographical aspects, field-emission scanning electron microscopy and transmission electron microscopy analyses were done. The Fourier transform infrared analysis generates the fingerprint of the synthesized phosphors confirming the presence of all constituent elements. The photoluminescent (PL) characteristics of synthesized phosphors were studied on exciting CaZrO3:Eu3+, Tb3+ with 225 nm, BaZrO3:Eu3+, Tb3+ with 229 nm and SrZrO3:Eu3+, Tb3+ with 235 nm excitation wavelength. The PL emission spectra show variable emissions over a broad spectral region corresponding to 5D4–7F6, 5D4–7F5, 5D4–7F4 and 5D4–7F3 hypersensitive electronic transitions of Tb3+ ions along with 5D0–7F0, 5D0–7F1 and 5D0–7F2 induced electric dipole and magnetic dipole transitions of Eu3+ ions. These color tunable phosphors with increased PL output confirm their suitability for photonics, optoelectronics and display device applications.

Effect of Fe3+ ion doping on photocatalytic ability of nanozirconia ceramic to degrade 2, 4, 6- trichlorophenol

Pure and a series of Fe3+ doped zirconia nanopowders were synthesized combining colloidal chemistry and solvothermal method from organometallic precursors in order to correlate doping and properties of zirconia matrix. After annealing of washed nanopowders at 600 °C, detailed characterization was performed using X-ray diffraction, UV/Vis absorption and luminescence, infrared and electron paramagnetic spectroscopy, transmission electron microscopy and BET measurements. Zirconia samples had mixed monoclinic and tetragonal crystalline phase; increasing Fe3+ ions concentration was followed by increasing of tetragonal phase share. In the sample with highest Fe3+ concentration, hematite can be detected. Also, UV/Vis spectrophotometry showed that Fe3+ doping lowers effective band gap of zirconia matrix from 4.5 eV (bulk value) to 2.1 eV for doped/nanocomposite samples. EPR measurements proved presence of dopant and showed that isolated Fe3+ ions in zirconia matrix exist in both crystalline phases; monoclinic and tetragonal (g ~ 4.8 and g ~ 4.27–4.2, respectively) surroundings. Zirconia samples were also successfully used as photocatalysts for photocatalytic degradation of 2, 4, 6, trichlorophenol.

Structural and Electrical Properties of Pulsed Laser Deposited Yttrium Doped Zirconium Oxide Thin Film Stabilization

Structural and Electrical Properties of Pulsed Laser Deposited Yttrium Doped Zirconium Oxide Thin Film Stabilization

Synthesis and characterization of metal-doped zirconia minispheres by sol-gel based freeze drying method

As the addition of metal dopant is expected to improve the application versatility of zirconia minispheres, the present study, reports the development of zirconia minispheres by adding metal dopants iron and copper individually and also together as a hybrid combination with zirconia in various weight percentage using sol-gel based freeze drying method.The developed metal doped zirconia minispheres were calcinated at elevated temperatures. Both calcinated and uncalcinated minispheres were characterizedfor identifying their thermal stability, absorption, crystalline, morphological and conductance behaviors. It was found that the calcinated zirconia minispheres doped with copper and iron in a hybrid combination possess good conductance, higher thermal stability, and a stable crystalline structure.

Enhancement of thermal properties of ytterbium-cerium oxide by zirconium doping for thermal barrier coatings

ABSTRACTRare-earth cerium oxides (RE2Ce2O7, RE = rare-earth elements) are proposed as promising thermal barrier coatings (TBCs) material due to large thermal expansion coefficient (TEC), phase stability and a comparable thermal cycling life to Yttria-Stabilized Zirconia (YSZ). However, the thermal conductivity of RE2Ce2O7 is relatively higher than that of both YSZ and rare-earth zirconates. Here, we report an effective method of reducing the thermal conductivity of Yb2Ce2O7 by Zr-doping. It is shown that, due to the strong phonon scattering caused by mass and radius differences between Ce4+ and Zr4+ ions, and disorder introduced into structures, the thermal conductivity of solid solutions is remarkably reduced with the increasing of Zr4+ content. Considering the high TEC, the Zr-doped Yb2Ce2O7 solid solutions are believed to be promising candidate materials for TBCs at elevated temperature.

Optical behavior and TL kinetics of Eu3+ and Tb3+ doped zirconate thermoluminescent phosphors

The influence of Tb3+ and Eu3+ ions on the optical behavior and TL kinetics of the synthesized phosphors were analyzed here. The AZrO3 (A = Ca, Ba, Sr) phosphors activated with Eu3+ and Tb3+ ions were prepared using solid state reaction technique. The doping concentration of Eu3+ and Tb3+ ions is varied from 0 to 2 mol% for each. The PXRD analysis is done to study various crystallographic aspects of synthesized phosphors. It confirms the crystalline structure, phase purity and homogeneity of synthesized phosphors. The FESEM and TEM analyses show formation of particles with irregular shape and variable dimensions. The agglomeration of these particles is a resultant of prolonged heat treatments involved in solid state reaction method at elevated temperatures. The study of TL spectra of UV and gamma irradiated phosphors set forth their second order kinetics. The electrons were trapped in trap centers with high trap depth and hence high amount of energy (~ 3 eV) is required to vacate them. The doping of trivalent rare earth impurity ions in the perovskite host lattice leads to formation of these traps centers. With enhanced TL intensity and low fading characteristics, these phosphors are suitable alternatives for TL mapping and sensing applications.

Biodiesel Production from Tannery Waste using a Nano Catalyst (Ferric-Manganese Doped Sulphated Zirconia)

ABSTRACT In this study, biodiesel was prepared using fat from tannery waste in the presence of a nanocatalyst, Ferric-Manganese Doped Sulfated Zirconia (Fe-Mn-SO4/ZrO2). After its preparationthe catalyst was characterized by modified wetness impregnation method. The effect of the various parameters influencing the biodiesel process was studied and optimized. A maximum biodiesel yield of 96.6 wt% was obtained when the optimized conditions were 12:1 methanol to fat, catalytic loading of 6 wt% at 65°C with a stirring rate of 450 rpm for 300 min. Furthermore, a catalyst reusability study was conducted to check the performance during recycling. It was observed that the catalyst can be recycled upto five times giving an yield above 90 wt%. Finally, the biodiesel properties were analyzed and compared with ASTM standards.

The Effect of Zirconium Doping on Solution-Processed Indium Oxide Thin Films Measured by a Novel Nondestructive Testing Method (Microwave Photoconductivity Decay)

Solution-processed indium oxide is an ideal transparent semiconductor material with wide band gap. Zirconium is an element characterized by a strong binding ability to oxygen which can inhibit the formation of oxygen vacancies and reduce the surface defect state. In this paper, zirconium doped indium oxide (InxZryO) thin films were prepared by the solution method, with indium oxide being doped with zirconium in order to tune the relative number of oxygen vacancies. The influence of the Zr doping concentration and the post-annealed temperature on the properties of the InxZryO thin films was investigated. The results show that the doping process improves the crystallinity and relative density of the obtained films. A novel nondestructive method named microwave photoconductivity decay (μ-PCD) was used to evaluate the quality of InxZryO thin films by simply measuring their response under laser irradiation. The relative number of oxygen vacancies and the minority carrier concentration achieved minimum values at 10 at.% Zr doping concentration. Furthermore, InxZryO thin films with optimal properties from an electrical point of view were obtained at 10 at.% Zr doping concentration, annealed at 400 °C. Characterized by an average transmittance above 90% in the visible range, the obtained InxZryO thin films can be used as active layer materials in the fabrication of high-performance thin film transistor (TFT) devices.

Passivation of silicon substrate using two-step grown ternary aluminium doped zirconium oxide

Ternary based aluminium doped zirconium oxide (AlxZryOz) was grown on silicon (Si) substrate after post-sputter oxidation of the AlZr film at different temperatures (400–1000 °C). Mixed phases (monoclinic + tetragonal) of AlxZryOz films were formed in all of the investigated films, accompanied with generation of oxygen vacancies (Vo). The presence of Vo favoured the hopping of oxygen molecules for oxidation to take place, leading to the formation of Al-Zr-Si-O interfacial layer (IL). The saturation of lattice with oxygen at high temperature (800 and 1000 °C) encouraged the trapping of additional oxygen as interstitials at the AlO network. Owing to the competition of both Vo and interstitials, microcracking was found on the film surface. Subsequent investigation was focused on the film obtained at 600 °C to study frequency dependent characteristics (dielectric constant, dielectric loss, interface state density, and series resistance) through capacitance-voltage and conductance-voltage measurements at different frequencies.

Highly sensitive non-enzymatic MP sensor based on electrospun copper oxide-doped zirconium oxide composite microfibers

An optimized detecting methyl parathion (MP) electrochemical sensor, fluorine tin oxide (FTO) electrodes modified by copper oxide doped zirconium oxide microfibers (CuO-ZrO2-MFs), has been successfully prepared. The CuO-ZrO2-MFs were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction pattern (XRD). The electrochemical and electrocatalytic performances of the CuO-ZrO2-MFs were investigated by cyclic voltammogram (CV) and square-wave voltammogram (SWV). The CuO-ZrO2-MFs as non-enzymatic MP sensor shows high sensitivity of 0.002–200ppb and low detection limit of 0.16ppb (signal/noise radio (S/N)=3), which are among the best values reported in literature. Additionally, excellent selectivity and reproducibility have also been observed.

Structure and Conductivity Studies of Scandia and Alumina Doped Zirconia Thin Films

In this work, scandia-doped zirconia (ScSZ) and scandia–alumina co-doped zirconia (ScSZAl) thin films were prepared by electron beam vapor deposition. X-ray diffraction (XRD) results indicated a presence of ZrO2 cubic phase structure, yet Raman analysis revealed the existence of secondary tetragonal and rhombohedral phases. Thus, XRD measurements were supported by Raman spectroscopy in order to comprehensively analyze the structure of formed ScSZ and ScSZAl thin films. It was also found that Al dopant slows down the formation of the cubic phase. The impedance measurements affirmed the correlation of the amount of secondary phases with the conductivity results and nonlinear crystallite size dependence.