Effect Of Zr4 Research Articles

Effect of Zr4+ on the microstructure and electrical properties of 0.6Y2O3-0.4YCr0.5Mn0.5O3 NTC ceramics

In this study, 0.6Y2O3-0.4YCr0.5Mn0.5O3 negative temperature coefficient (NTC) ceramics doped with different ZrO2 contents were prepared using a two-step sintering method. The effects of Zr4+ content on the microstructure and electrical properties of 0.6Y2O3-0.4YCr0.5Mn0.5O3 were mainly investigated. For the microstructure, X-ray diffraction (XRD) reveals the presence of two main crystalline phases in the samples: Y2O3 and YCr0.5Mn0.5O3. Scanning electron microscopy (SEM) reveals a clear two-phase appearance, and the porosity tends to decrease with the addition of ZrO2. Combined with energy dispersive spectrometer (EDS) to derive the distribution of the elements, Zr4+ is mainly present in the Y2O3 phase, with a small amount in the YCr0.5Mn0.5O3 phase. In addition, the grain sizes of different groups were counted, and the grain size of Y2O3 decreased from 2.73 ± 1.80 μm to 1.65 ± 0.93 μm with the increase of ZrO2 content. For the electrical properties, the resistance-temperature curves were measured from 298.15 K to 1073.15 K, and all the samples exhibited NTC characteristics. And with the increase of ZrO2 content, the resistivity increased from 1.91 × 107 Ω cm to 1.96 × 108 Ω cm, and the B25/100 value decreased from 3315 K to 1310 K. In addition, the chemical state forms of the elements on the surface of the samples were analysed by X-ray photoelectron spectroscopy (XPS), and the valence states as well as the occupancy of the transition elements Cr and Mn were analysed in detail according to the principle of multiple splitting. Finally, the mechanism of influence on microstructure and electrical properties is explained by combining the theory of grain boundary migration and thermal ceramic conductivity.

Effect of Zr4+ concentration on optical properties and defect structure of Zr:Ho:LiNbO3 crystals

Effect of Zr4+ concentration on optical properties and defect structure of Zr:Ho:LiNbO3 crystals

Effect of Zr4+ concentration on the segregation coefficient and exposure energy of Zr:Fe:Cu:LiNbO3 crystal

A series of Zr:Fe:Cu:LiNbO3 crystals with distinct Zr4+ ion doping concentrations (0, 2, and 4 mol%) were grown using the Czochralski method. Subsequently, the segregation coefficient of doped ions in the crystal was analyzed by an inductively coupled plasma-atomic emission spectrometer. The lattice constant and defect structure of the crystal were measured by X-ray powder diffraction. The light-induced scattering of Zr:Fe:Cu:LiNbO3 crystal was analyzed by the threshold effect of incident exposure energy flux and the same as the change in Zr4+ ion doping concentration. When the Zr4+ ion concentration changes to 4 mol%, the exposure energy was close to 811.37 J/cm2, which is about 192 times that of the 0 mol% Zr4+.

Effect of Zr4+ substitution on the phase evolution and microwave dielectric properties of (Cu1/3Nb2/3)0.25Ti0.75-xZrxO2 ceramics

The effect of Zr4+ substitution for Ti4+ on the phase evolution and microwave dielectric properties of (Cu1/3Nb2/3)0.25Ti0.75-xZrxO2 (0 = x ≤ 0.35) ceramics prepared via conventional solid-state method has been investigated. With the increase of Zr substitution, the ceramics exhibit a gradual phase transition from a tetragonal rutile phase to an orthorhombic srilankite phase, where the synthesis of the srilankite phase at atmospheric pressure and temperature below 1200 °C in this study is reported for the first time. The crystal structure is tetragonal rutile type for the unsubstituted composition, orthorhombic srilankite type for the compositions with x > 0.30, and the compositions in between is a two-phase region with a mixture of rutile and srilankite. The Zr substitution has a great influence on the microstructure of the ceramics. In particular, for compositions where x > 0.1, the grain boundaries are surrounded by elongated powdery particles. The microwave dielectric properties of the ceramics are closely related to the phase transition process, in which Q × f is significantly improved and τf decreases almost linearly with the increase of the content of srilankite phase. Optimum microwave dielectric properties with a permittivity of 35.1, a Q × f value of 7270 GHz, and a near-zero τf of 9.0 ppm/°C are obtained in the ceramics with x = 0.3 sintered at 1150 °C for 4 h, which provides a new option for microwave devices requiring medium-permittivity dielectric ceramics.

Effect of Zr4+ on piezoelectric, dielectric and ferroelectric properties of barium calcium titanate lead-free ceramics

[Formula: see text][Formula: see text]([Formula: see text][Formula: see text][Formula: see text](BCTZ) ceramics with [Formula: see text] 0.05, 0.10, 0.15, 0.20, 0.25, 0.30 were prepared by the solid-state reaction method. Calcination of the powders was carried out at 1100 [Formula: see text]C for 4 h and the green pellets were sintered at 1400 [Formula: see text]C for 2 h. X-ray diffraction patterns of the sintered pellets showed tetragonal splitting up to [Formula: see text] 0.10 while the mixture of the rhombohedral/cubic phase appeared at higher ZrO2 concentrations. Maximum piezoelectric charge constant [Formula: see text] 510 pC/N and strain ([Formula: see text] 0.103%) were measured for BCT doped by 0.10 mol ZrO2. Dielectric constant, remnant polarization and saturation polarization also found maxima for this composition. The Curie temperature ([Formula: see text] of the compositions decreased with increase in ZrO2 concentration and reached 98 [Formula: see text]C, 87 [Formula: see text]C and 36 [Formula: see text]C at [Formula: see text] 0.05, 0.10, 0.15 mol, respectively. The remaining compositions have [Formula: see text] below the room temperature; therefore, they can be used for subzero/cryogenic applications. The scanning electron microscopy study revealed an increase in grain size with increase in ZrO2 concentration and confirmed the complete solubility of ZrO2 in the crystal lattice. Overall, low ZrO2-doped BCT compositions with high [Formula: see text] could be suitable for low temperature (<80 [Formula: see text]C) applications.

Effect of Zr4+ on the structural and microwave dielectric properties of CaTiO3 ceramics

The new ceramic composite of Ca(ZrxTi1-x)O3 had been prepared using the conventional mixed oxide solid state reaction method. The effects of Zr4+ ions substation over Ti4+ ions on the microwave dielectric properties of the CaTiO3 ceramics were investigated. The phase analysis showed that the specimens Ca(ZrxTi1-x)O3 presented single phase with orthorhombic structure in the range of x = 0.0–0.7 when sintered at 1300 °C for 3 h. The addition of Zr4+ facilitated the formation of large round-like grains with porous microstructure. The solid solution with x = 0.7 sintered at 1300 °C for 3 h showed a good combination of dielectric properties: and (at 2.5 GHz).

Preparation of Zr4+ doped calcium hexaaluminate with improved slag penetration resistance

AbstractAiming to improve the density of calcium hexaaluminate (CA6), Zr4+ doped CA6 with the structural formula of CaAl11.73◊0.25Zr0.02O18.41◊0.59 (CaAl11.73Zr0.02O18.41) was successfully synthesized at 1600℃ for 4 h in air. The effect of Zr4+ doping on the crystal structure of CA6 was investigated using first principle calculation, structure refinement in combination with experimental characterization. The results suggest that Zr4+ prefers to substitute the Al3+ at Al3 site, which can increase the lattice parameter of c‐axis and the amount of Al vacancies. The average thickness of Zr4+ doped CA6 is increased by approximate 36% in comparison with the pure one. In addition, molecular dynamics (MD) simulation indicates that Zr4+ doping can reduce the wettability of CA6 to slag to some extent. The reaction test method was carried out and it shows that CA6 with Zr4+ doping possesses better slag penetration resistance. Based on this, the reaction mechanism is also discussed.

Effect of Zr4+ doping on the morphological features and electrochemical performance of monoclinic Li3V2(PO4)3/C cathode material synthesized by an improved sol-gel combustion technique

Abstract Monoclinic Li3V2−xZrx(PO4)3/C composites with different Zr4+ doping amounts (x = 0.00, 0.01, 0.05 and 0.09) were prepared by an improved sol-gel combustion technique. An expansion in the lattice volume was caused by the incorporation of Zr4+ in the V3+ sites of Li3V2(PO4)3, thus providing enlarged Li+ diffusion channels that are conducive to the reversible intercalation and deintercalation of Li+. Moreover, the amount of Zr4+ doping had an obvious impact on the morphological characteristics of Li3V2(PO4)3, while the undoped Li3V2(PO4)3 contained a mixed morphology with porous particles and needles. The volume fraction and sizes of the needles decreased with increasing amounts of Zr4+ doping. No needles were observed when the amount of Zr4+ doping was increased to x = 0.09. Furthermore, the ohmic and charge-transfer resistances were reduced, and the reversibility and Li+ diffusion coefficient were improved, after Zr4+ doping. All Zr4+-doped samples displayed better electrochemical performance when compared to pristine Li3V2(PO4)3. The optimized Li3V1.95Zr0.05(PO4)3/C sample with an adequate level of Zr4+ doping exhibited the highest tap density and demonstrated excellent electrochemical properties. It delivered a specific discharge capacity of 112.2 mAh g−1 at 10 C rate and a high capacity retention of 86.1% over 1000 cycles ranging from 3.0 to 4.3 V.

Effect of Zr4+ on the properties of layered structured Ba(Ti1−x Zr x )4O9 perovskites

ABSTRACT Solid solutions of Ba(Ti1−x Zr x )4O9 (0 ≤ x ≤ 0.8) were fabricated via mixed oxides, solid state route. The phase, microstructural and dielectric properties of the fabricated samples were investigated. A structural phase transition was observed from orthorhombic (Amm2) to tetragonal (P4/mmm) with increasing Zr4+ contents (x ≥ 0.6). The dielectric constant (ϵr ) increased with the substitution of Zr4+ contents which may be attributed to the larger ionic size and higher polarisability of Zr4+ relative to Ti4+. The maximum ϵr of 48.27 was observed for x = 0.2. The lowest dielectric loss (tan δ) of 5.5 × 10−4 and maximum quality factor (Q × f) of 5.6 × 104 MHz were obtained (at 30 MHz) for Ba(Ti0.8Zr0.2)4O9 ceramics sintered at 1300°C for 2 h in air.

Effect of Zr4+ Dopant on Microstructure, Densification and Thermomechanical Behaviour of ZnAl2O4 Spinel

Effect of Zr4+ Dopant on Microstructure, Densification and Thermomechanical Behaviour of ZnAl2O4 Spinel

Effect of Zr4+on the phase stability and oxygen permeation characteristics of SrCo0.8Fe0.2−yZryO3−δ (y ≤ 0.1) membranes

A stable and high oxygen permeable membrane system has been developed via partial replacement of iron with zirconium in SrCo0.8Fe0.2O3−δ compound. The initial powder series of composition SrCo0.8Fe0.2−yZryO3−δ (0 ≤ y ≤ 0.1), synthesized by an oxalate-based sol-gel route, is shown to exhibit a single perovskite-type cubic phase at 27 °C, transform to a brownmillerite (Ca2AlFeO5)-type orthorhombic structure, and finally assume a stable open cubic phase with disordered oxygen vacancies at temperatures determined by zirconium content, transitions being at 200 and 800 °C, respectively for the system y = 0.05. The highest JO2 of 2.54 × 10−6 mol cm−2 s−1 is realized in optimum composition of y = 0.05 at 1000 °C. The formation of cubic phase in Sr–Co–Fe–O system with abundance of disordered anion vacancies is crucial for both the high oxygen permeability and extended operational stability at elevated temperatures.

Effects of Zirconium Ions Doping on the Structural and Thermochromic Properties of VO2 Thin Films

As an inorganic functional material, VO2 thin films are expected to be used for smart windows. However, these films are not conducive to practical applications when the phase transition temperature (Tc) of the VO2 is approximately 68°C, which is greater than room temperature. To decrease Tc, the effect of Zr4+ doping on the structure and properties of VO2 films were investigated. The films were prepared using a sol–gel process, spin-coating on quartz glasses, and annealing at 525°C in a tube furnace within a nitrogen atmosphere. The results demonstrate that these films have a highly preferential crystalline orientation on the substrate; however, the primary two x-ray diffraction pattern peaks shift slightly toward the small angle, and when 7 at.% Zr4+ was doped in the VO2 film, the deviation angle was 0.16°, and the crystallite size was approximately 98 nm. A large number of grains were found on the surface of the pure VO2 films, but all the Zr4+ doped films had a layered structure, and the thickness of the films was approximately 200 nm. The Tc of these films was characterized using differential scanning calorimetry, and the luminous and solar transmittance was characterized using a UV–Vis–NIR spectrophotometer, which demonstrated that the effect of Zr4+ doping decreased Tc by approximately 1°C per 1 at.% on average, and the Tc of the 7 at.% film was slightly greater than that of the 5 at.% film, the phase transition temperature of which was 61.4°C. The transmittance decreased as the doping concentration increased, and 1 at.% Zr4+ doping increased the luminous regulation efficiency (ΔT lum) and solar modulation efficiency (ΔT sol). The ΔT lum of the pure VO2 film and the 1 at.% Zr4+-doped VO2 films was 10.9% and 11.2%, and ΔT sol was 14.4 and 15.2%, respectively.

Comparative Study on the Effect of Zr4+ and Ca2+ Doping on the Properties of NiO

The comparative study was made on the effect of Zirconium ions (Zr4+) and Calcium ions (Ca2+) dopant on NiO properties. The electroceramic of Ni(1-x)ZrxO and Ni(1-x)CaxO was prepared by using solid state reaction method. The different amount of Zr4+ was studied. XRD analysis on sintered sample showed the single phase formation of Ni(1-x)ZrxO and Ni(1-x)CaxO. The dielectric behavior of Ni(1-x)ZrxO with x = 0.02 mole % Zr4+ exhibited highest dielectric constant (700) with moderate dielectric loss (0.16). Meanwhile, the dielectric behavior of Ni(1-x)CaxO samples show that the sample doped with x = 0.01 mole % Ca2+ obtained the lowest dielectric loss (0.05) but moderate in dielectric constant (123), measured at 1MHz.

Ba[Mg<sub>(1-</sub><italic><sub>x</sub></italic><sub>)/3</sub>Zr<italic><sub>x</sub></italic>Nb<sub>2(1-</sub><italic><sub>x</sub></italic><sub>)/3</sub>]O<sub>3</sub>微波介质陶瓷的红外光谱

Ba[Mg(1- x )/3Zr x Nb2(1- x )/3]O3 (BMZN, x =0, 0.10, 0.15) microwave dielectric ceramics were synthesized at 1520℃ using the conventional solid-state sintering technique. Effect of Zr4+ substitution on crystal structures and dielectric properties of the BMZN ceramics was studied by far-infrared spectroscopy (FIR). The results show that with increasing Zr4+ concentration the IR active modes near 370 cm-1 split and new phonon modes appear; the IR active modes near 410 cm-1 disappear; the frequencies of the IR active modes near 230, 290 and 540 cm-1 shift towards high frequency and the intensities of these modes decrease. Studies about the FIR spectra show that with increasing Zr4+ concentration the crystal structures of the BMZN ceramics transformed from hexagonal to cubic structure. The correlations between dielectric properties and IR modes were established with vibration modes as the media.

Effect of Zr4+ Content on the Grain Growth, Dielectric Relaxation Behavior, and Ferroelectric Properties of Ba0.4Sr0.6Ti1−x Zr x O3 Nano-Ceramics Prepared by Different Methods Assisted by Fast Microwave Sintering

The effect of Zr4+ content on the grain growth, dielectric relaxation, and piezoelectric properties of Ba0.4Sr0.6Ti1−xZrxO3 (BSTZ; x = 0, 0.02, 0.04, 0.06) ceramics prepared by solid-state (SS) and sol–gel modified hydrothermal (SH) methods assisted by fast microwave sintering was investigated in this study. A combination of x-ray diffraction (XRD), scanning electron microscopy (SEM), impedance analysis, and ferroelectric analysis was used. All the ceramics had pure perovskite structures at room temperature, as seen from XRD patterns, indicating that Zr4+ was incorporated into Ba0.4Sr0.6TiO3 lattices to form a solid solution. In the SEM micrographs, SH samples had higher densities and smaller and more homogeneous grain size than SS samples, which was in agreement with density measurements. Nano-ceramics were obtained by this method. When the temperature dependence of dielectric constant and dielectric loss was studied, SH samples had higher permittivity, better thermally activated relaxation, and lower dielectric loss at high temperature. Ferroelectric characteristics can still be detected in Ba0.4Sr0.6Ti1−xZrxO3 ceramics and residual polarization (Pr) decreased with increasing Zr4+ content.

Effect of Zr4+ content on the TC range and dielectric and ferroelectric properties of BaZrxTi1−xO3 ceramics prepared by microwave sintering

Single phase and dense BaZrxTi1−xO3 (BZT) ceramics (x=0.05, 0.1, 0.15, 0.2, 0.25) were obtained by microwave sintering and the powders of these ceramics were synthesized by conventional hydrothermal method. The microstructural, dielectric and ferroelectric properties of BaZrxTi1−xO3 ceramics sintered at 1300oC were investigated. The XRD analysis revealed that the synthesized compound was formed with no second phase. As x was increased from 0.05 to 0.25, the average grain size was observed on the SEM micrographs to decrease from ~6μm to ~3μm. The dielectric constant as a function of temperature showed a decrease in Curie temperature (TC) with an increasing x, while the maximum value of dielectric loss occurred (tanδ) at x=0.1. A ferroelectric-relaxor crossover was observed to take place with increasing x by using the modified Curie–Weiss law. The remnant polarization (Pr) decreased from 9.45 to 4.4C/cm2 with an increasing x, while the maximum value of Pr=11.84 also occurred at x=0.1. The breadth of TC range increased rapidly when x<0.15, but no significant difference was observed with further doping of Zr4+. The full width at half maximum (FWHM) was used to show the degree of the broadening in Curie peak.

Flash Synthesis of Tetragonal-ZrO&lt;sub&gt;2&lt;/sub&gt; Nanostructures by Microwave-Induced Combustion Process

The synthesis used urea and Zr (NO3)4·5H2O as material to prepare tetragonal-ZrO2 nanocrystals through microwave-induced combustion process. The tetragonal-ZrO2 nanocrystals were characterized by X-ray diffraction (XRD). The effect of Zr4+/urea molar ratio on the synthesis of tetragonal-ZrO2 were studied. It was found that tetragonal-ZrO2 crystal would be better when the Zr4+/urea molar ratio was larger than 1:3.The SEM images of the samples showed the hollow structures formed at different levels of molar ratio of Zr4+/urea. This method is a simple but effective route to prepare tetragonal-ZrO2 nanocrystals.

Effect of Zr4+ substitution on thermal stability and electrical properties of high temperature BiFe0.99Al0.01O3–BaTi1−xZrxO3 ceramics

High-temperature Pb-free ceramics of 0.72BiFe0.99Al0.01O3–0.28BaTi1−xZrxO3 (BFA–BZxT) have been prepared through solid state reaction route. The influence of the Zr4+ substitution for Ti4+ on microstructure, thermal stability and electrical properties of the BFA–BZxT ceramics was investigated. The results showed single-phase solid solutions occurred for compositions x=0–0.12 and a morphotropic phase boundary (MPB) separating rhombohedral and pseudocubic phases existed near x=0.03. The substitution of Zr4+ for Ti4+ caused significant change of grain size for BFA–BZxT ceramics. The optimum piezoelectric properties of d33=157pC/N, kp=0.33, combined with improved depoling temperature Td=425°C, are obtained around the MPB composition of x=0.03. The results indicate that BFA–BZxT ceramics have a great potential to apply in high temperature field.

Efficient fabrication of ZrO2-doped TiO2 hollow nanospheres with enhanced photocatalytic activity of rhodamine B degradation

ZrO2-doped TiO2 hollow nanospheres with anatase phase are efficiently fabricated via functionalized negatively charged polystyrene (PS) spheres without any surfactant or polyelectrolyte. The resulting Ti1−xZrxO2 (hereafter denoted as TZ) hollow nanospheres are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Laser Raman spectroscopy (LRS), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence spectroscopy (XRF), nitrogen sorption, and UV–vis diffuse reflectance spectroscopy (UV–vis). The Zr4+ incorporation decreases the anatase crystallite size, increases the specific surface area, and changes the pore size distribution. Furthermore, it induces enrichment of electron charge density around Ti4+ ions and blueshift of absorption edges. The TZ hollow nanospheres doped with moderate ZrO2 (molar ratio, Ti:Zr=10:1) exhibit better photocatalytic activity than the other samples for the degradation of rhodamine B in aqueous solution, which is correlated with the effect of Zr4+ doping on the physicochemical properties in terms of surface structures, phase structures, and the electronic structures.

Effect of Zr4+-ion substitution in CeO2 on H2O2-assisted degradation of orange G

Abstract A series of Pd ion-substituted CeO2–ZrO2 solid solutions were synthesized using the solution combustion technique. H2O2-assisted degradation of orange G was carried out in the presence of the catalysts. The activity of the catalysts was found to increase with the introduction of the second component in the solid solution, as signified by an increase in the rate constants and lowering of activation energy. The study showed the involvement of lattice oxygen and the importance of reducibility of the compound for the reaction.