O3 System Research Articles

Low-temperature liquid precursors of crystalline metal oxides assisted by heterogeneous photocatalysis.

The photocatalytically assisted decomposition of liquid precursors of metal oxides incorporating TiO2 particles enables the preparation of functional layers from the ferroelectric Pb(Zr,Ti)O3 and multiferroic BiFeO3 perovskite systems at temperatures not exceeding 350 ºC. This enables direct deposition on flexible plastic, where the multifunctionality provided by these complex-oxide materials guarantees their potential use in next-generation flexible electronics.

A temperature-stable and high-Q microwave dielectric ceramic of the MgTiO3–(Ca0.8Sr0.2)(Zr0.1Ti0.9)O3 system

The (1−x)MgTiO3(MT)–x(Ca0.8Sr0.2)(Zr0.1Ti0.9)O3(CSZT) ceramic system prepared by using the conventional solid state method was investigated in terms of its microstructures and microwave dielectric properties. To achieve a temperature-stable material, two compounds with negative and positive temperature coefficients were used to form mixed phases. The microwave dielectric properties are strongly correlated with composition. For practical application, a dielectric constant (εr) of 22.1, a quality factor (Q×f value) of 116,000GHz, and a temperature coefficient of resonant frequency (τf) of 5ppm/°C for 0.95MgTiO3–0.05(Ca0.8Sr0.2)(Zr0.1Ti0.9)O3 sintered at 1300°C for 4h are proposed.

Dielectric Properties and Impedance Spectroscopy of MnCO3‐Modified (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 Lead‐Free Ceramics

A MnCO3‐modified (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 system was synthesized by solid‐state reaction method. The phase structure, microstructure, electrical properties, and complex impedance were investigated in detail. The addition of small amount of MnCO3 was quite effective to lower the sintering temperature. XRD analysis showed that the single perovskite phase was achieved in all compositions. XPS results demonstrated that the Mn ions were present in the mixed valence form of +2 and +4. The existence of Mn2+ ions gave rise to an increase in oxygen vacancies and suppressed the piezoelectric and ferroelectric properties of samples. The diffusive phase transition was enhanced while the Curie temperature was remained in the vicinity of 90°C. In addition, according to the impedance analysis, it was concluded that the dielectric relaxation behavior was non‐Debye type and the movements of singly ionized oxygen vacancies played an important role in the conduction behavior at higher temperatures.

Oxygen-vacancy and charge hopping related dielectric relaxation and conduction process in orthorhombic Gd doped YFe0.6Mn0.4O3 multiferroics

The temperature dependent dielectric relaxation and conduction mechanism of multiferroic Y1−xGdxFe0.6Mn0.4O3 (0⩽x⩽0.8) systems have been investigated by dielectric measurements and impedance spectroscopy study in the temperature range of 150–550K. We have observed that the charge carrier hopping (with activation energy of 0.18–0.4eV) and doubly ionized oxygen vacancy VO (activation energy of 0.4–0.6eV) are mainly responsible for conduction mechanism in the systems. Conducting charge-relaxation-mode interaction may be the plausible reason for high dielectric constant in the samples. The XPS analysis reveals that the valence states of the Mn and Fe ions are tuned between Mn3+/Mn4+ and Fe3+/Fe2+ states depending upon the change in oxygen vacancy with different Gd concentrations. The activation energy increases with increase in Gd content revealing the increased oxygen vacancy concentration with increasing Gd content in high temperature region. The relaxation process is dominated by the short range hopping of charge carriers resulting in a departure from ideal Debye-like behavior. The samples possess two different conduction mechanisms that have different activation energies above and below their spin reorientation transition temperature.

Temperature stable high K microwave dielectric ceramics of Bi3NbO7 doped by V2O5

Low firing microwave dielectric ceramics Bi3(Nb1−xVx)O7 (x=0.0, 0.1, 0.2, 0.3, and 0.5) were prepared by the solid state reaction method. Sintering behavior, crystalline structure, microstructure, and microwave dielectric properties were studied. Temperature stable low-firing microwave dielectric ceramics with high permittivity were obtained in the Bi3(Nb1−xVx)O7 system when x=0.1 and 0.2. The Bi3(Nb0.9V0.1)O7 and Bi3(Nb0.8V0.2)O7 ceramics sintered at 870°C for 2h were found to possess high permittivity of 80 and 76, Qf (quality factor) values of 615 and 460GHz, and TCF (temperature coefficient of frequency) values of −22 and+3.3ppm/°C, respectively.

Optimization and interpretation of O3 and O3/H2O2 oxidation processes to pretreat hydrocortisone pharmaceutical wastewater

Chemical synthetic pharmaceutical wastewater must be pretreated before traditional biological treatment to improve the biodegradability of pollutants due to their high concentration and complex composition. This study investigated O3 and O3/H2O2 systems to pretreat hydrocortisone wastewater. The optimum treatment efficiency of the O3 system was achieved under pH value of 5.76, dosage of O3 of 217.5 mg/L, and reaction time of 90 min. The removal efficiency of chemical oxygen demand (COD) and total organic carbon (TOC) was 94% and 92%, respectively. The ratio of biochemical oxygen demand (BOD) and COD (B/C) increased from 0.066 to 0.310. Moreover, the optimum H2O2/O3 molar ratio was 0.3 with the optimum pH of 3, and reaction time was reduced to 15 min to reach COD removal efficiency of 67.3% in the O3/H2O2 oxidation system. Interestingly, isobutanol was assumed to be a good hydroxyl radical trapping agent due to the great decrease of Fenton reagent reaction rate constant. By comparing two different kinetic models, oxidation mechanism could be interpreted by the pseudo first-order kinetic model with the high correlation coefficient R2 above 0.9787. It can be concluded that ozonation system was controlled by both direct oxidation and free radical oxidation, and particularly the later one played a dominant role.

Dielectric, Piezoelectric Properties and Temperature Stability of (Na,K)(Nb,Sb)O3 System Ceramics

In this study, in order to develop lead-free composition for piezoelectric actuator applications, (Na0.525K0.48-x)(Nb0.92-xSb0.08)O3 + 0.25wt%Bi2O3 + xLiTaO3 (x = 0.036, 0.037, 0.038, 0.039, 0.040) composition ceramics were fabricated by the normal sintering technique. The piezoelectric properties of resultant ceramics were studied with a special emphasis on the varying of LiTaO3. The structure of the specimen exhibits an orthorhombic perovskite structure. The grain size of the specimen increased with increasing the content of LiTaO3 substitution. High physical properties of the piezoelectric constant d33 = 317 pC/N, electromechanical coupling factor kp = 0.466, dielectric constant ϵr = 1913, and density ρ = 4.527 g/cm3 were obtained from the composition ceramics with x = 0.037. Also, at this composition, Δkp/kp20°C and Δfr/fr20°C showed the maximum value of −0.041 and −0.022 at −20°C and 50°C, respectively. Accordingly, it is considered that the temperature stability of x = 0.037 composition ceramics is suitable for the application of the piezoelectric actuator.

Investigation of the dielectric relaxation processes in PbZr0.65Ti0.35O3–BaFe12O19 multiferroic ceramic composites

The dielectric relaxation processes have been investigated in multiferroic ceramic composites based on the ferroelectric PbZr0.65Ti0.35O3 (PZT) and ferrimagnetic BaFe12O19 (BaM) systems. The frequency dispersion of the complex dielectric permittivity was analyzed over wide frequency and temperature ranges, and the effect of BaM content is depicted. The activation energies for the relaxation processes were also obtained for all the studied compositions and the results suggest the oxygen vacancies-related hopping mechanism to be responsible for the observed behaviors in the studied composites. Furthermore, an anomalous behavior in the activation energy has been observed with the increase of the BaM concentration. The obtained results are discussed within the framework of current models reported in the literature for dielectric relaxation processes.

Quest for lead free relaxors in YIn(1-x)Fe(x)O₃ (0.0 ≤ x ≤ 1.0) system: role of synthesis and structure.

The B-site tailored YIn(1-x)Fe(x)O3 (0.0≤ x≤ 1.0) series was synthesized by glycine-aided gel-combustion technique and subjected to extensive structural and electrical investigations. The temperature had tremendous bearing on the phase evolution exhibited by the system. The entire system crystallized as C-type metastable polymorph in the as-synthesized form. Hexagonal polymorphs of Fe(3+)-rich compositions could be isolated by controlled heat treatment at 750 °C. Raman spectroscopic investigations showed that, while there is a general shrinkage of the lattice due to substitution of a smaller ion at In(3+)-site, there is an apparent dilation of the Y-O bond, and this anomaly reflects in the electrical behavior exhibited by the system. The single-phasic hexagonal nominal compositions, YIn(1-x)Fe(x)O3 (0.0 ≤ x ≤ 0.3), were also studied by impedance spectroscopy. The dielectric constant was found to drastically increase from 10 for YInO3 to 1000 for YIn(0.7)Fe(0.3)O3 at room temperature stressing the role of B-site tailoring on electrical behavior. More interestingly, careful substitution of Fe into YInO3 could tune the electrical behavior from a dielectric to relaxor ferroelectric in the temperature range studied. The nominal composition YIn(0.7)Fe(0.3)O3 showed a classical relaxor ferroelectric like behavior which is an important observation in context of the search for new lead free relaxor materials.

Theoretical prediction of ozone sensing using pristine and endohedral metalloboron B80 fullerenes

The adsorption of ozone on B80 and endohedral Be@B80 fullerenes is ascertained with density functional theory. The potential energy curve of ozone adsorption on pristine and endohedral B80 fullerenes is investigated. Obtained data indicate that the behavior of O3 adsorption on investigated fullerenes can be better described by Corrected-Morse potential equation. On the basis of results, the ozone can be adsorbed onto the outer surface of pristine B80 molecule with adsorption energy of −327.34kJmol−1. The tangible adsorption energy of O3 onto the B80 and relatively bond length of BO (∼1.45Å) in B80/O3 system imply that this structure is of highly stability. Compared the calculated adsorption energy of O3 adsorbed on Be@B80 system (−498.87kJmol−1) with pristine B80, indicate that when the metal atom encapsulated into the B80 fullerene, the adsorption of ozone on Be@B80 is more favorable than pristine B80. Also, the presence of Be metal atom can be improved the oxidation process of B80 fullerene. During the oxidation process of Be@B80 fullerene using ozone, the Be metal atom translated from the center to wall of the B80 and strongly bonded to the boron atoms of inner walls. Based on our results, it seems that ozone tends to be chemisorbed onto the B80 and Be@B80 fullerenes with appreciable adsorption energy, whereas the Be@B80 fullerene is more favorable than pristine B80. Furthermore, due to the disappeared some energy level near the LUMO and decreased the Eg, the electrical conductance of the B80/O3 and Be@B80/O3 systems are increased. In conclusion, pristine B80 and Be@B80 fullerenes can be converted the presence of O3 molecule directly to an electrical signal, and therefore, it can be potentially used as ozone sensor.

Effect of composition on the pressure-driven ferroelectric to antiferroelectric phase transformation behavior of (Pb0.97La0.02)(Zr1−x−ySnxTiy)O3 ceramics

Power can be generated by rapidly driving a poled ferroelectric material through a ferroelectric to antiferroelectric phase transformation. The power generated depends on the maximum remnant polarization that can be obtained in the ferroelectric state and the minimum dielectric permittivity that can be obtained in the antiferroelectric state. In this study, the effect of composition on these properties was measured for compositions in the (Pb0.97La0.02)(Zr1−x−ySnxTiy)O3 system. Specimens were fabricated and characterized in the ferroelectric and antiferroelectric state under hydrostatic loading. The results are discussed in terms of their impact on an energy harvesting cycle that utilizes a ferroelectric to antiferroelectric phase transformation. The calculated maximum theoretical energy density based on the measurements was 14.5 J/cm3.

Synchrotron X-ray absorption spectroscopy study of local structure transformation behavior in perovskite Ba(Ti,Zr)O3 system

In this work, the change of the local atomic structure in BaTi1−xZrxO3 ceramics was investigated by synchrotron X-ray absorption spectroscopy technique. The X-ray Absorption Near-Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) spectra at the Ti K-edge were measured and compared with simulated spectra. The results show that an increase of Zr content in Ba(Ti,Zr)O3 lattice structure affected significantly the phase transition behavior and the local structure surrounding the Ti absorbing atom. More importantly, the information on the locally determined structures and its relation to the phase transition characteristic from relaxor ferroelectric to polar clusters in Ba(Ti,Zr)O3 system were obtained and discussed.

Sulfamethoxazole degradation by ultrasound/ozone oxidation process in water: Kinetics, mechanisms, and pathways

In this research, sulfamethoxazole (SMX) degradation was investigated using ultrasound (US), ozone (O3) and ultrasound/ozone oxidation process (UOOP). It was proved that ultrasound significantly enhanced SMX ozonation by assisting ozone in producing more hydroxyl radicals in UOOP. Ultrasound also made the rate constants improve by kinetics analysis. When ultrasound was added to the ozonation process, the reaction rate increased by 6–26% under different pH conditions. Moreover, main intermediates oxidized by US, O3 and UOOP system were identified. Although the main intermediates in ozonation and UOOP were similar, the introduction of ultrasound in UOOP had well improved the cleavage of S–N bond. In this condition SMX become much easier to be attacked, which led to enhanced SMX removal rate in UOOP compared to the other two examined processes. Finally, the SMX degradation pathways were proposed.

High Power Performance of Manganese‐Doped BNT‐Based Pb‐Free Piezoelectric Ceramics

Electromechanical properties and high power characteristics of Pb‐free hard piezoelectric ceramics in the (BiNa0.88K0.08Li0.04)0.5 (Ti1−xMnx)O3 (x = 0, 0.014, 0.015, and 0.016) system were studied. Mn doping resulted in a considerable enhancement of mechanical quality factor Qm and vibration velocity. The lowest mechanical and dielectric losses were achieved in 1.5 mol% Mn‐doped ceramics with a planar Qm of about 970 and tanδ of 0.89%. The heat dissipation and resonance frequency shift under high drive condition were remarkably suppressed upon Mn doping. The maximum vibration velocity was increased from 0.28 m/s in undoped ceramic to 0.6 m/s in 1.5 mol% Mn‐doped composition. The results of this study revealed that Mn‐doped BNT‐based piezoelectrics exhibited a superior high power performance compared to their lead‐based counterparts such as PZT4 and PZT8 ceramics.

Off-Stoichiometric Nickel Cobaltite Nanoparticles: Thermal Stability, Magnetization, and Neutron Diffraction Studies

In the present investigation, we report a detailed examination of the effect of off-stoichiometry introduced in NiCo2O4 by adding excess cobalt. Thus, we compare and analyze the structural and magnetic properties of the Ni0.75Co2.25O4 and NiCo2O4 cubic systems. A low temperature combustion method was utilized to synthesize stoichiometric (NiCo2O4) and off-stoichiometric (Ni0.75Co2.25O4) nanoparticles on a large scale. The X-ray diffraction pattern for the sample annealed at high temperature (773 K) shows the presence of a much less intense NiO phase (∼2–5%) in Ni0.75Co2.25O4 as compared to that in the case of NiCo2O4 sample (∼15–20%). The Ni 2p and Co 2p XPS spectra reveal the coexistence of Ni2+, Ni3+, Co2+, and Co3+ species on the surface of both the NiCo2O4 and Ni0.75Co2.25O4 samples in differing proportions. In addition to the basic magnetic characterizations using PPMS, these were also analyzed by neutron diffraction. The off-stoichiometric Ni0.75Co2.25O4 sample shows an interesting magnetic phase conversion from frustrated dipolar system to an enhanced magnetic ordering upon annealing. Local moments on the lattice sites of NiCo2O4 and Ni0.75Co2.25O4 samples are further compared by neutron diffraction confirming stronger ordered moments and enhanced structural and thermal stability for the Ni0.75Co2.25O4 sample.

Decomposition of phenylarsonic acid by AOP processes: degradation rate constants and by-products.

The paper presents results of the studies photodegradation, photooxidation, and oxidation of phenylarsonic acid (PAA) in aquatic solution. The water solutions, which consist of 2.7 g dm(-3) phenylarsonic acid, were subjected to advance oxidation process (AOP) in UV, UV/H2O2, UV/O3, H2O2, and O3 systems under two pH conditions. Kinetic rate constants and half-life of phenylarsonic acid decomposition reaction are presented. The results from the study indicate that at pH 2 and 7, PAA degradation processes takes place in accordance with the pseudo first order kinetic reaction. The highest rate constants (10.45 × 10(-3) and 20.12 × 10(-3)) and degradation efficiencies at pH 2 and 7 were obtained at UV/O3 processes. In solution, after processes, benzene, phenol, acetophenone, o-hydroxybiphenyl, p-hydroxybiphenyl, benzoic acid, benzaldehyde, and biphenyl were identified.

Effect of Pr- and Nd- doping on structural, dielectric, and magnetic properties of multiferroic Bi0.8La0.2Fe0.9Mn0.1O3

Bi0.8La0.15RE0.05Fe0.9Mn0.1O3 (where RE = Pr and Nd) have been prepared via conventional solid state route. The Rietveld refinement of X-ray diffraction patterns shows that both systems crystallize in orthorhombic Pnma space group. Raman modes observed for these two systems indicate that both systems are very close to orthorhombic Pnma structure. Appearance of prominent A1-3 and weak E-2 modes in Bi0.8La0.15Nd0.05Fe0.9Mn0.1O3 indicate the presence of chemically more active Bi-O covalent bonds (which favors stereochemical activity of Bi lone pair electrons) in comparison to Bi0.8La0.15Pr0.05Fe0.9Mn0.1O3. Moreover, Bi0.8La0.15Nd0.05Fe0.9Mn0.1O3 system shows higher dielectric constant, low dielectric loss, and higher magnetization value in comparison to Bi0.8La0.15Pr0.05Fe0.9Mn0.1O3 system. Ferroelectric transition temperature decreases to 460 °C for both systems in comparison to 710 °C of Bi0.8La0.2Fe0.9Mn0.1O3. The improved dielectric and magnetic response suggests Bi0.8La0.15Nd0.05Fe0.9Mn0.1O3 a better multiferroic system than Bi0.8La0.15Pr0.05Fe0.9Mn0.1O3.

Structural phase transitions of robust insulating Bi1-xLaxFe1-yTiyO3 multiferroics

In contrast to leaky BiFeO3, of which two structural phase transitions of cycloidal modulated antiferromagnetic-paramagnetic and ferroelectric-paraelectric are observed below 850 °C, chemical co-substitution to form Bi1−xLaxFe1−yTiyO3 ternary solid solution makes these multiferroic ceramics become robust insulating low dielectric loss and exhibit rich structural phase transitions. Differential thermal analysis and temperature-dependent X-ray diffraction measurements probe four first-order structural phase transitions, e.g., TH = 305 °C, TN = 365 °C, TC = 810 °C, and TS = 830 °C observed in the Bi0.98La0.02Fe0.99Ti0.01O3 system, which are reasonably attributed to Brazovskii-type cycloidal modulated antiferromagnetic-helimagnetic (at TH) and helimagnetic-paramagnetic (at TN) magnetic phase transitions, ferroelectric-paraelectric (at TC) and rhombohedral-cubic (at TS) structural phase transitions, respectively. Magnetic phase transition temperatures change a little but ferroelectric and lattice structural phase transition temperatures decrease gradually with increasing co-substitution up to composition-induced rhombohedral-(pseudo-)cubic structural phase boundary. The first-order nature of magnetic phase transition and emergence of helimagnetic phase were attributed to Ti3+ d1 magnetic disorder distribution in the Fe3+ d5-O-Fe3+ d5 chains, while the first-order nature becomes weak with increasing co-substitution, owing to decreased ferroelectric rhombohedral lattice distortion. An intermediate rhombohedral paraelectric phase is discovered intervening between ferroelectric rhombohedral and paraelectric cubic phase, of which the temperature range defined by difference between TC and TS increases with increasing co-substitution. It was found that TC and TS are able to be predicted quantitatively by reduced mass of unit cell. These findings enrich our understanding of ferroic phase transitions and advance designing novel high temperature multiferroic compounds.

Shift of morphotropic phase boundary in high-performance fine-grained PZN–PZT ceramics

Abstract The fine-grained xPb(Zn1/3Nb2/3)O3–(1 − x)Pb(Zr0.47Ti0.53)O3 system has been prepared from submicron precursor powders obtained by high-energy ball milling method. The addition of PZN induces a decrease of grain size from an initial micron scale to a submicron scale, accompanying with the phase transition from tetragonal to morphotropic phase boundary (MPB), and then rhombohedral side. Interestingly, compared to the former published data for coarse-grained ceramic, the MPB has shifted from 50% to 30% PZN content side due to the enhancement of the internal stress for fine-grained ceramic. The enhanced electrical and mechanical performances are closely associated with the phase structure and grain size. A high piezoelectric property (d33 = 380 pC/N and kp = 0.49) as well as mechanical performance (Hv = 5.0 GPa and KIC = 1.33 MPa m1/2) were obtained simultaneously for the MPB 0.3PZN–0.7PZT ceramics with an average grain size of 0.65 μm.

Electrical properties of Sn-doped Ba0.75Sr0.25Ti0.95O3 perovskite

The aim of this paper is to study the structural and the electrical properties of Ba0.75Sr0.25Ti0.95Sn0.05O3 system, synthesized by the solid state reaction method. The material was structurally characterized by X-ray diffraction and transport measurements have been made using impedance spectroscopy technique. From DC conductance analysis, we found that insulator–metal transition is not observed in the temperature range of the study. The electronic conduction has two different processes. The first one is dominated by thermally activated hopping of small polaron, at high temperatures, and another one by variable range hopping, at low temperatures. Impedance spectrum results indicated that the electrical properties are strongly dependent on temperature. Nyquist plots showed that the dielectric response is accurately fitted by the Cole–Cole model and represented by an equivalent circuit which consists of a parallel combination of a resistance and a constant phase element. From this analysis, the evidence of grain boundary conduction has been observed.