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Sodium niobate thin films doped with manganese (NN), and NN films modified with 5 or 10 mol % calcium zirconate (CZ) on platinized silicon substrates were prepared by chemical solution deposition. The 250-nm-thick films crystallize in a perovskite phase with fine, equiaxed grains. The NN films exhibit well-shaped ferroelectric loops with a remanent polarization and coercive field of ∼10 μC/cm2 and ∼100 kV/cm, respectively. The modification with CZ strongly influences the ferroelectric response of the films: the remanent polarization progressively decreases to around 2.5 μC/cm2. The absence of an anti-ferroelectric response, which has previously been confirmed in bulk NN-CZ ceramics, is attributed to the nanoscale microstructure and residual thermal stresses. All the studied films exhibit a piezoelectric response with the highest piezoelectric d33 coefficient of 35 pm/V at 300 kV/cm bias field for the NN modified films with 5 mol % CZ, making them candidates for lead-free piezoelectric thin-film applications.

Concentration of oxide ion vacancies and its ordering in crystalline lattices play an important role in the structural, optical and ionic transport properties of RE2O3–MO2 (RE (Rare earths), M = Ti, Zr, Hf) systems. Rarely investigated rare earth zirconate system, RE4Zr3O12 (RE = Dy, Y, Er, and Yb) exhibiting the polymorphic structural forms, was chosen for the present study. RE4Zr3O12 nanoceramics were prepared through an auto-ignited combustion method; thereafter, dense bulk ceramics were derived from them at relatively low temperatures. X-ray diffraction studies carried out on the nanoceramics as well as bulk ceramics suggest defect fluorite structure for RE = Dy, Y and Er whereas δ-phase rhombohedral structure for RE = Yb ceramics. Extent of oxide ion ordering and the structural variations due to the replacement of rare earth ions in the crystalline lattices were analyzed by Raman and infrared spectroscopy. UV–Visible and photoluminescence spectroscopy were employed to investigate the optical properties of the nanoceramics. Impedance spectroscopic studies carried out on the bulk ceramic materials show that the oxide ion hopping conduction mechanism in the bulk ceramics was affected by the structural factors and free mobile oxide ion concentration. Increase of total electrical conductivity of the dense ceramics with the increase of temperature was in accordance with the Arrhenius relation. Electrical conductivity of fluorites was higher than the δ-phase ceramics, which was attributed to the decreased activation energy and increased available number of mobile oxide ions in the fluorite structure.

Ternary oxide powders based on titania, zirconia and silica have been synthesized by the sol–gel method. The characterization of the powders was performed using UV–Vis spectroscopy, EPR, X-ray diffraction and Raman spectroscopy. The XRD study indicated the formation of TiO2 nanocrystals in anatase phase and titanium zirconate as srilankite phase. The band gap energy values of ternary powders are in the range of 3.2–3.3 eV. It is found that different types of paramagnetic centers were formed depending on silica sources after high-energy irradiation. As shown by the electron paramagnetic resonance study, the stability of SiO2 against β-irradiation is observed only for TiO2/ZrO2/SiO2 powder obtained from tetraethoxysilane as well as the formation of oxygen vacancies in TiO2 structure. Photocatalytic activity of TiO2/ZrO2/SiO2 powders is investigated in the process of photoreduction of Cr(VI) ions to Cr(III). As shown, the efficiency of photocatalyst depended on the nature of defect sites of the nanocomposites’ surface. It is found that the TiO2/ZrO2/SiO2 system obtained using tetraethoxysilane exhibited the highest photocatalytic activity as a result of the certain defect sites formation after high-energy irradiation.

Manganese-doped lead zirconate ceramics were prepared by a conventional solid reaction method. Although the doping content varies from 5% (mole) to 20% (mole), significantly enhanced universal dielectric relaxation occurs only in 5% Mn-doped lead zirconate. The behavior cannot be properly explained by Maxwell-Wagner relaxation, which is commonly used for explaining giant dielectric permittivity in electroceramics. It is found that the enhanced giant dielectric permittivity is related to hetero-valence cation doping induced universal dielectric relaxation.

Technology is suggested for fabrication of ceramic piezoelectric materials from the lead-containing ferroelectric phase. The technology includes a low-temperature synthesis of ultradispersed lead titanate and zirconate powders and also of phases of solid solutions on their basis and the low-temperature procedure for sintering of ceramic fabricated from ultradispersed powders of ferroelectric phases. As precursors used in the suggested low-temperature synthesis serve lead glycerate and tartrate. It was found that, when interacting (at temperatures of 240–330°C) with hydroxo-peroxo-aqua complexes of titanium and(or) zirconium(IV) in the course of 30–40 min, the precursors form ultradispersed powders of these phases, which are single-phase and contain particles with average size of less than 100 nm. It was shown that using the suggested technology makes it possible not only to reduce the energy expenditure for separate procedures for synthesis of ultradispersed ferroelectric phases and for synthesis of piezoelectric materials, but also to substantially diminish the discharge of lead(II) compounds into the atmosphere of industrial premises. It was also shown that the technology enables fabrication of piezoelectric materials with prescribed values of electrical parameters.

The pyrochlore oxides are of potential interest as ion conducting electrolyte for intermediate temperature solid oxide fuel cell (SOFC). Nanopowders of holmium zirconate have been synthesised through ion-exchange between sodium alginate gel and metal complex solution followed by its thermal decomposition. Nanoparticles of Ho2Zr2O7 were obtained by calcining the dried gel beads at 700 °C for 2 h and 6 h duration respectively. An insight into calcination has been obtained employing simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). Thermal decomposition was also followed using High Temperature X-ray Diffraction (HTXRD) in static ambient atmosphere. Results from TGA/DSC and HTXRD corroborate with each other. Fine crystalline nanopowders of single phase Ho2Zr2O7 could be obtained after thermal decomposition at relatively low temperature (600–700 °C). Powder X-ray diffraction (XRD) revealed that the material has crystallized as single phase cubic Ho2Zr2O7 with defect fluorite structure. XRD and Raman spectroscopy were used to analyse the local structure of holmium zirconate. XRD scans of holmium zirconate and holmium hafnate prepared through identical method have been compared and the effect of cationic radius of Zr4+ and Hf4+ on B-site was studied. The crystallographic data obtained from XRD and transmission electron microscopy (TEM) are in good agreement with each other. This sol-gel method also referred as Leeds Alginate Process (LAP) is simple, cost effective, energy efficient and carbon neutral for the preparation of pyrochlore oxides (A2B2O7) solid electrolyte material for SOFC.

Barium strontium zirconate titanate ceramics ((BaSr)(ZrTi)O3-BSZT) with Zr4+ ionic contents of 15 and 20 mol % and Sr2+ ionic contents of 15, 20, 25, and 30 mol % were prepared using a solid-state reaction approach. X-ray diffraction and scanning electron microscopy were used to characterize the lattice structure and morphologies of the ceramics. Permittivity and polarization as a function of temperature were characterized using an impedance analyzer and a Tower–Sawyer circuit. The electrocaloric effect was measured directly and calculated using the Maxwell relation (indirectly). The results indicated that the BSZT ceramics change from a normal ferroelectric to a relaxor ferroelectric with increasing Zr4+ ionic content, which can be further modified by the addition of Sr2+ ionic content. The optimized adiabatic temperature change ΔT obtained is 2.43 K in (Ba0.85Sr0.15)(Zr0.15Ti0.75)O3 ceramics, and ΔT >1.6 K over a wide temperature span of 120 °C was obtained.

In this letter, we report the energy storage capacity and magneto-dielectric tenability of rare earth zirconates, by synthesizing a series of Ce-substituted neodymium zirconates having general formula, Nd2Zr2−xCexO7 (x = 0.0, 0.4, 0.8, 1.2, 1.6 and 2.0), using sol–gel auto-combustion method. Linear ferroelectric response and energy storage efficiency was checked from polarization loops. Magnetic characterization revealed that rare earth zirconates had small values of coercivity and remanence which argued mainly a superparamagnetic nature of the samples. Tailoring of dielectric properties with the magnetic field and a possible origin of magneto-dielectric coupling was also investigated.

The biofunctionalization of metal implants with bioactive ceramics arises as an appealing strategy for promoting their osseointegration, without impairing implants’ good mechanical resistance. In this work, biocomposites of hydroxyapatite - CaZrO3 were obtained by rate controlled sintering and their microstructure, mechanical properties, biological as well as the effect of stoichiometric calcium zirconate dopant on the decomposition of HA were analysed. The results obtained showed that the addition of CaZrO3 stabilizes the hydroxyapatite at least up to 1300 °C and inhibits the appearance of the α- and β-TCP phases. Moreover, the mechanical properties of the hydroxyapatite were improved with 10 wt% of CaZrO3, despite the increase of porosity. The in vitro assays demonstrated that the biocomposites were biocompatible, since they favoured human osteoblast cells adhesion and proliferation. All the data obtained emphasize the potential of these biocomposites for the aimed biomedical application.

The performance of low-to-intermediate temperature (400–800 °C) solid oxide fuel cells (SOFCs) depends on the properties of electrolyte used. SOFC performance can be enhanced by replacing electrolyte materials from conventional oxide ion (O2-) conductors with proton (H+) conductors because H+ conductors have higher ionic conductivity and theoretical electrical efficiency than O2- conductors within the target temperature range. Electrolytes based on cerate and/or zirconate have been proposed as potential H+ conductors. Cerate-based electrolytes have the highest H+ conductivity, but they are chemically and thermally unstable during redox cycles, whereas zirconate-based electrolytes exhibit the opposite properties. Thus, tailoring the properties of cerate and/or zirconate electrolytes by doping with rare-earth metals has become a main concern for many researchers to further improve the ionic conductivity and stability of electrolytes. This article provides an overview on the properties of four types of cerate and/or zirconate electrolytes including cerate-based, zirconate-based, single-doped cerate–zirconate and hybrid-doped cerate–zirconate. The properties of the proton electrolytes such as ionic conductivity, chemical stability and sinterability are also systematically discussed. This review further provides a summary of the performance of SOFCs operated with cerate and/or zirconate proton conductors and the actual potential of these materials as alternative electrolytes for proton-conducting SOFC application.

Using Nd and Ce with the ratio of 1:5 as simultaneous substitutions of trivalent and tetravalent actinides in gadolinium zirconate, a series of Gd2-xNdxZr2-5xCe5xO7 (0 ≤ x ≤ 0.4) ceramics were prepared by rapid microwave sintering with a co-precipitation assisted solvothermal synthesized nanocrystalline powders. The simulated proportional nuclear waste disposal behaviours were identified by various characterization methods. XRD results show that when x is less than 0.4, all samples only have the single defect fluorite structure, while Gd1.2Ce0.8O3.2 is formed in Gd1.6Nd0.4Ce2O7 as x raise to 0.4. The relative density and average grain size both increase with the elevation of sintered temperature and x value. Sintering maps show that the obvious grain growth happens when x ≥ 0.3 and the densification processes can occur at different sintering temperatures with different x values.

Ceramics powders based on cerate-zirconate such as yttrium-doped barium cerate-zirconate, BaCe0.54Zr0.36Y0.1O3 (BCZY) have been used as electrolyte materials for proton-conducting fuel cell (PCFC) application. High purity of the ceramics powders are traditionally prepared by solid state reaction (SSR) method at a high processing temperature (> 1400 °C). Alternatively, sol-gel (SG) technique and high pressure – high temperature (HP-HT) batch wise reactor system using supercritical fluids (SCFs) method are introduced to synthesis the powders at a lower temperature. To achieve the goals in producing the ceramics powders with better properties than SSR method, few critical parameters for both SG and SG assisted SCFs methods are determined. This study reports the effects of different chemical agents (chelating agent and surfactant) in SG method and the effects of pressure and temperature of HP-HT batch wise reactor system using ethanol as solvent on the phase purity and microstructure of the BCZY powders. Chelating agent (triethylenetetramine, TETA) and surfactant (Brij-97) aided to produce a single perovskite phase of BCZY at calcination temperatures of 1100 °C and 950 °C, respectively. On the other hand, a single perovskite phase of BCZY was obtained via SCFs assisted with sol-gel (SG-SCFs) method. The optimum characteristics of BCZY powder was found in the one prepared at P = 2 MPa and T = 150 °C and 200 °C. Particles of the powders produced by SG and SG-SCFs methods are spherical in-shape. As proven, SG method is able to produce better phase purity and homogenize BCZY powder at lower processing temperature that meets criteria to be used as an electrolyte material.

The critical need for clean energy has led to the development of lead-free electroceramics. However, lead-free antiferroelectrics seldom have been reported because of the difficulties in materials fabrication and their low electrical performance. In this work, we successfully synthesized lead-free antiferroelectric ceramics (1-x)AgNbO3-xCaZrO3 (x = 0.00–0.01) using the solid state reaction method in flowing oxygen (O2) atmosphere. Calcium zirconate (CaZrO3) dopant effectively stabilized the antiferroelectricity of silver niobate (AgNbO3) by dramatically decreasing the tolerance factor t. Additionally, we identified an orthorhombic Pbcm structure similar to that of pure AgNbO3. With the introduction of CaZrO3, phase transition temperatures M1–M2, M2–M3 and the freezing temperature Tf decreased. The shift of the M1–M2 phase transition temperature and Tf was the result of the restriction of the M1 phase due to CaZrO3 substitution. The compositions of x

Zirconium and hafnium compounds are widely used in today’s technology. Zirconium or hafnium carbides and borides are high temperature ceramics.The present study concerns primarily with optimizing the extraction of zirconium and hafnium from their naturally occurring mineral, zircon, via a wet chemical process. First , zircon heated with molten sodium hydroxide to form zironate and silicate frit. Simple separation technique of sodium silicate from the zirconate and hafnate sodium was then applied to obtain a silicate-free frit, then the extraction of the zirconium ( IV ) and hafnium ( IV ) basic sulfates from their oxychloride solution leaving almost all other ions soluble in the mother liquor was achieved by adjusting the pH value. The precipitate of zirconium ( IV ) and hafnium ( IV ) basic sulfates was dried, weighed, analyzed and percent of the zirconium and hafnium extracted were found to be 97 % of their original concentration.

In the present work, Gadolinium zirconate (GZ) films were prepared by laser CVD (LCVD) method. The influence of preparation conditions, involving preheating temperature (Tpre) and laser output power density (Pl) on morphology, microstructure, substrate temperature (Tsub) and deposition rate was thoroughly investigated. An extended formation region of GZ films, based on Tpre and Pl values, was observed at a pressure of about 0.9 kPa. Laser irradiation mainly plays a photolytic role when Pl

Mg, as a new dopant, has been found to stabilize the desired cubic garnet structure (Ia 3 ¯ d) of Li-La-zirconate (LLZO) and lead to Li-ion conductivities similar to those obtained with the same level of Al-doping. More importantly, Mg-doping, as opposed to Al-doping, suppresses the deleterious reactions with the atmospheric moisture/CO2, leading to stability in the composition-phase-structure upon exposure to air. Accordingly, when exposed to air, even though Al-doped LLZO pellets get spontaneously fractured/disintegrated, accompanied by reduction in ionic conductivity by ~3 orders of magnitude, Mg-doped LLZO shows no sign of cracking and almost retains the ionic conductivity measured prior to exposure.

La-Ce-Gd titanate-zirconate pyrochlore-based ceramics was synthesized at the lab-scale inductive melting unit with a 56 mm inner diameter cold crucible. Batch feeding rate and melting ratio were 3 kg/h and 3 kW h/kg respectively. The ceramics is composed of 85–90 vol% zoned grains of the pyrochlore structure phase, the sample has excellent chemical durability in hot water and may be considered as a promising matrix for actinide – rare earth fraction of high level waste.

This work employed an axial suspension plasma spray (SPS) process to deposit two different gadolinium zirconate (GZ) based triple layered thermal barrier coatings (TBCs). The first was a ‘layered’ TBC (GZ dense/GZ/YSZ) where the base layer was YSZ, intermediate layer was a relatively porous GZ and the top layer was a relatively dense GZ. The second triple layered TBC was a ‘composite’ TBC (GZ dense/GZ + YSZ/YSZ) comprising of an YSZ base layer, a GZ + YSZ intermediate layer and a dense GZ top layer. The as sprayed TBCs (layered and composite) were characterized using SEM/EDS and XRD. Two different methods (water intrusion and image analysis) were used to measure the porosity content of the as sprayed TBCs. Fracture toughness measurements were made on the intermediate layers (GZ + YSZ layer of the composite TBC and porous GZ layer of the layered TBC respectively) using micro indentation tests. The GZ + YSZ layer in the composite TBC was shown to have a slightly higher fracture toughness than the relatively porous GZ layer in the layered TBC. Erosion performance of the as sprayed TBCs was evaluated at room temperature where the composite TBC showed higher erosion resistance than the layered TBC. However, in the burner rig test conducted at 1400 °C, the layered TBC showed higher thermal cyclic lifetime than the composite TBC. Failure analysis of the thermally cycled and eroded TBCs was performed using SEM and XRD.

The following paper presents study on synthesis and thermal diffusivity of europium zirconate, cerate and hafnate as a new types of materials with pyrochlore or fluorite type of lattice, dedicated to replacement of conventional 8YSZ ( yttria stabilized zirconia ) in TBC ( thermal barrier coatings ) systems for aircraft gas turbines. All materials were synthesized via solid-state reaction ( SSR ) preceded preparation of powder mixtures (mechanical milling in ethanol). The feedstock powders were characterized by analysis of crystallite size, particle size distribution and phase composition. On the base of DSC measurements, the parameters of high temperature sintering were selected (1350 °C/2 h/15 MPa). Structural characterization of obtained materials inclusive analysis of morphology, chemical and phase composition of sinters was performed. Thermal diffusivity was measured in temperature range 25÷1400 °C by laser flash analysis ( LFA ). The obtained materials with pyrochlore and fluorite type of lattice exhibit lower thermal diffusivity compared to that of yttria-stabilized zirconia at high temperatures. In particular, the most promising material in view of insulating properties is Eu 2 Ce 2 O 7 , which exhibit much lower thermal diffusivity than Eu 2 Zr 2 O 7 and Eu 2 Hf 2 O 7 , especially at temperature higher than 1000 °C. However, in temperature range 25–700 °C, europium hafnate and zirconate exhibit lower thermal diffusivity compared to that of europium cerate and 8YSZ.

Heterointerfaces introduce unique localized defects into ionic conductors. This study explores the nanoionic characteristics exhibited by the proton-conducting oxides SrZr0.9Y0.1O3-δ and SrCe0.95Yb0.05O3-δ including finely dispersed precipitated platinum nanoparticles. The electrical conductivity of both the platinum-doped oxides revealed reversible nanoionic phenomena caused by the exsolution of the platinum in the form of platinum nanoparticles, at 0.5 vol% relative to the metal oxides, and dissolution in response to a change in gas atmosphere. In comparison with the original conductivity of SrZr0.9Y0.1O3-δ and SrCe0.95Yb0.05O3-δ, the conductivity of platinum-doped SrZr0.9Y0.1O3-δ decreased significantly in a wet hydrogen atmosphere, whereas platinum-doped SrCe0.95Yb0.05O3-δ showed almost no decrease in conductivity in the same atmosphere. The different responses of the two materials to the change in gas atmosphere are discussed in relation to the precipitation of platinum nanoparticles.

Nowadays, the contribution of rare-earth oxide compounds is extensively investigated with the aim to improve the service life of gas turbine engine components protected by thermal barrier coatings (TBCs) against the environmental Calcia-Magnesia-Alumino-Silicate (CMAS) attack. Therefore, the TBCs consisting of a NiCrAlY bond coat, Yttria Stabilized Zirconia (YSZ) and/or mixture of YSZ and Gadolinium Zirconate (YSZ+GZ) interlayers, and a GZ top coat, which were all deposited by atmospheric plasma spraying onto the nickel-based superalloy substrates, are introduced in this contribution. The CMAS-attack resistance was evaluated using an indirect method. Firstly, the thin layer of CMAS prepared from colloidal solutions was deposited onto the top coat surface and, after drying, the samples were heat treated with the aim to glassified the CMAS. Secondly, the coated samples containing CMAS glass debris were subjected to rapid heating (up to 1200 °C) and enforced cooling cycles at the burner-rig test device and the failure of TBC was investigated. In all cases, the failure mechanism due to the CMAS attack was the top coat spallation. The functional graded TBC was found to be the most resistant system.

In this work, three double layered thermal barrier coating (TBC) variations with different gadolinium zirconate (GZ) and YSZ thickness (400GZ/100YSZ, 250GZ/250YSZ and 100GZ/400YSZ respectively, where the prefixed numbers before GZ and YSZ represent the layer thickness in μm), were produced by suspension plasma spray (SPS) process. The objective was to investigate the influence of YSZ thickness on the thermal conductivity and thermal shock lifetime of the GZ/YSZ double layered TBCs. The as sprayed TBCs were characterized using SEM, XRD and porosity measurements. Thermal diffusivity measurements were made using laser flash analysis and the thermal conductivity of the TBCs was calculated. The double layered TBC with the lowest YSZ (400GZ/100YSZ) thickness showed lower thermal diffusivity and thermal conductivity. The double layered TBCs were subjected to thermal shock test at a TBC surface temperature of 1350 °C. Results indicate that the TBC with a higher YSZ thickness (100GZ/400YSZ) showed inferior thermal shock lifetime whereas the TBCs with low YSZ thickness showed comparatively higher thermal shock lifetimes. Failure of the TBCs after thermal shock test was analyzed using SEM and XRD to gain further insights.

In situ high-pressure experiments on La2Zr2O7 and La0.5Gd1.5Zr2O7 have been carried out at up to approximately 40 GPa using synchrotron X-ray diffraction and Raman spectroscopy combined with a diamond anvil cell technique. Both La2Zr2O7 and La0.5Gd1.5Zr2O7 undergo a phase transition from a pyrochlore phase (Fdm) into a cotunnite-like phase (Pnma) at 22.7 and 23.3 GPa, respectively. This type of phase transition is mainly controlled through the order-disorder occupancy of cations, and Gd3+ substitution of La3+ reduces the stability of zirconate pyrochlore. However, abnormal changes to the unit-cell volumes and vibrational modes observed at 5.5 GPa in La2Zr2O7 and 6.5 GPa in La0.5Gd1.5Zr2O7 are attributed to an anion disorder in the pyrochlore.

In recent years, research is focused on the development of rare earth zirconates based thermal barrier coatings (TBC). In the present study, bilayered 8 wt% yttria stabilized zirconia (YSZ)/gadolinium zirconate (GZO) TBC system has been developed by atmospheric plasma spraying (APS) process from powders prepared by a single step co-precipitation technique. Hot corrosion behavior of all the coatings are tested in fused Na2SO4 + V2O5 mixture at the concentration of approximately 25 mg/cm2 at 910 °C for 30 h. Formation of gadolinium vanadate (GdVO4) is observed to be the corrosion product in YSZ/GZO bilayer coatings from Energy Dispersive X-ray analysis (EDAX) and is further confirmed by X-ray diffractometry (XRD) analysis. FESEM cross-section analysis of the YSZ/GZO bilayer coating after corrosion test affirms the effectiveness of the bilayer design in preventing the penetration of corrosive salts to the YSZ layer. Also, YSZ/GZO bilayer TBC exhibited a higher thermal cyclic life (300 cycles) than the single layer 8YSZ (175 cycles) coatings at 1100 °C.

Yttria-stabilized zirconia (YSZ) thermal barrier coatings is most widely used in gas turbine engines applications and its primary role is to protect the underlying base metal from degradation at its high temperature (>1000 °C) service environment. While YSZ serves well in this role, materials with higher thermal stability and lower thermal conductivities are required to be developed for attaining higher operating temperatures and thereby higher energy conversion efficiencies. A number of rare-earth zirconates which form the cubic fluorite-derived pyrochlore structures (A2B2O7) where A: La, Gd, Sm, Ce and B: Zr are being developed, some compositions are more attractive due to their good amalgamation of thermal and mechanical properties. However, when these materials are plasma spray coated on metal substrates, the favorable properties are not immediately realized due to various contributing factors such as poor adhesion/cohesion, microstructure (porosity, defects) or even incomplete stabilization or destabilization of the desired phase (crystal structure) after passing through the plasma. In this paper, plasma sprayable powders of zirconate pyrochlores (or with disordered fluorite structures) synthesized from using La and Ce as the trivalent “A” cation, were plasma sprayed onto Inconel 718 substrates, by using different plasma spray parameters. The considerable influence of these spray parameters on the structural phases (analyzed via XRD) and microstructures (studied via SEM on polished cross section metallographs) are presented in detail.

In this work, a printed flexural plate wave (FPW) CO 2 sensor based on PZT-PDMS (Lead zirconate titanate-Polydimethylsiloxane) is prepared with simple fabrication techniques. The 2-port FPW resonator has a resonant frequency of 21.51 MHz with a low insertion loss of -3.3 dBm. Multi-Walled Carbon Nanotubes (MWCNT) solution is applied as sensing layer to measure CO 2 concentration in the surrounding. The sensitivity and limit of detection (LOD) of the sensor are measured to be 504 Hz/ppm and 6.7 ppm, respectively. The sensor shows good repeatability, response and recoveries to varying CO 2 concentrations. With adaptability to roll to roll (R2R) printing methods, this inexpensive and prototype FPW gas sensor shows potential for low concentration measurement of CO 2 .

In this study, First-Order Reversal Curves (FORC) measurements and impedance spectroscopy coupled to hyperbolic law analysis have been used in order to characterize lead zirconate antiferroelectric thin films elaborated by a sol-gel process. The presence of a weak residual ferroelectric behavior has been shown even if this contribution is not clearly visible on the polarization-electric field loops. Moreover, FORC measurements indicate that the weak ferroelectric phase switch only when the antiferroelectric phase state of the cell is modified. On the other hand, impedance spectroscopy reveals a fairly good distribution of small residual ferroelectric clusters in the material as no coalescence of ferroelectric domains has been observed at low fields. This study aims to show that FORC distribution measurements and impedance spectroscopy coupled to the hyperbolic law analysis are very sensitive and complementary methods for the understanding of the polarization switching dynamics in antiferroelectric materials.

A metal-ferroelectric-metal (MFM) capacitor was fabricated to investigate the effect of the rate-of-change of temperature in the rapid thermal annealing (RTA) process on the physical properties of the MFM capacitor’s ferroelectric layer [lead zirconate oxide (PZT)]. Remnant polarization (2 × Pr) is measured and monitored while performing the RTA process at 500 °C–700 °C. It turned out that, for a given target/final temperature in the RTA process, 2Pr of the ferroelectric layer decreases with a higher rate-of-change of temperature. This can provide a way to adjust the properties of the PZT layer, depending on the RTA process condition (i.e., using various rate-of-changes of temperature) for a given final/target temperature.

This study investigates the preparation and characterization of CaZr0.9Sm0.025Dy0.075O3-coated film system. The powder used for coating was prepared by solid-state ceramic route synthesis and spin coating technique was used to prepare the film of the CaZr0.9Sm0.025Dy0.075O3 system. Structural studies were carried out using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The XRD peaks of spin-coated system were indexed for an orthorhombic (Pnma) perovskite structure of CaZrO3. The film when excited at 350 nm yield blue-green emission at 482 and 571 nm, which corresponds to the transition from 4F9/2 to 6H15/2 and 6H13/2 levels of Dy3+ ion, respectively, and orange-red emission at 603 and 657 nm corresponds to the transition from 4G5/2 to 6H7/2 and 6H11/2 transitions of Sm3+ ions, respectively. CIE coordinates of the film show near-white light emission from the system.

Fatigue degradation is a significant problem in piezo/ferroelectric materials and their commercial applications. The major causes of electrical fatigue degradation are a domain pinning effect and physical damage such as microcracking. This work reports the fatigue behavior of barium calcium zirconate titanate (Ba0.85Ca0.15Zr0.1Ti0.9O3) under regular and low oxygen concentration silicone oil. Impedence analyzer and LCR meter are employed to analyzer the dielectric properties and it also revealed the relationship between activation energy and oxygen vacancy. X-ray diffraction, synchrotron X-ray absorption spectroscopy, and scanning electron microscope techniques were employed to study the local structural changes, defect development, physical damage and microcracking in the ceramics. FEFF-8.4 simulations were used to determine the oxygen vacancy creation. The study reveals the relationship of oxygen vacancy creation, domain wall pinning, microcracking and the fatigue behavior of the ferroelectric ceramic. The work investigated the dielectric and ferroelectric properties of BCZT ceramics intermes of applied electric field.

This research paper is concentrated on the design of biologically compatible lead-free piezoelectric composites which may eventually replace traditional lead zirconium titanate (PZT) in micromechanical fluidics, the predominantly used ferroelectric material today. Thus, a lead-free barium&ndash, calcium zirconate titanate (BCZT) composite was synthesized, its crystalline structure and size, surface morphology, chemical, and piezoelectric properties were analyzed, together with the investigations done in variation of composite thin film thickness and its effect on the element properties. Four elements with different thicknesses of BCZT layers were fabricated and investigated in order to design a functional acoustophoresis micromechanical fluidic element, based on bulk acoustic generation for particle control technologies. Main methods used in this research were as follows: FTIR and XRD for evaluation of chemical and phase composition, SEM&mdash, for surface morphology, wettability measurements were used for surface free energy evaluation, a laser triangular sensing system&mdash, for evaluation of piezoelectric properties. XRD results allowed calculating the average crystallite size, which was 65.68 &Aring, 3 confirming the formation of BCZT nanoparticles. SEM micrographs results showed that BCZT thin films have some porosities on the surface with grain size ranging from 0.2 to 7.2 &micro, m. Measurements of wettability showed that thin film surfaces are partially wetting and hydrophilic, with high degree of wettability and strong solid/liquid interactions for liquids. The critical surface tension was calculated in the range from 20.05 to 27.20 mN/m. Finally, investigations of piezoelectric properties showed significant results of lead-free piezoelectric composite, i.e., under 5 N force impulse thin films generated from 76 mV up to 782 mV voltages. Moreover, an experimental analysis showed that a designed lead-free BCZT element creates bulk acoustic waves and allows manipulating bio particles in this fluidic system.

International audience; Three long-term experiments have been performed in SOEC and SOFC modes at different operating temperatures. The durability tests confirm a higher degradation in electrolysis mode with respect to fuel cell operation. In addition, a larger increase of the ohmic resistance is observed for the cell operated at higher temperature in electrolysis mode. The oxygen electrodes of the pristine and tested cells have been characterized by synchrotron X-ray micro-diffraction and micro-fluorescence to assess the relation between the material destabilization and the formation of insulating phases due to interlayer diffusion. The analyses of the pristine cell confirm the presence after the electrode sintering of strontium zirconate and a Gd-rich inter-diffusional layer in the electrolyte just below the zirconates. Moreover, evolutions in the LSCF unit cell volume reveal strontium segregation after aging. The associated material destabilization is linked to the accumulation of SrZrO 3 at the barrier layer-inter-diffusional layer interface in operation and both phenomena are found to be thermally-activated and promoted in electrolysis mode. Finally, the crystallographic evolution of the inter-diffusional layer in electrolysis mode has been investigated by X-ray diffraction. A slight increase of the phase peaks intensity detected at the highest temperature is correlated to the largest formation of SrZrO 3 observed in this condition. Based on these preliminary results, it is proposed that the loss of Zr 4+ from the electrolyte due to the zirconates formation could facilitate the inter-diffusion of Gd, reducing the local ionic conductivity and thus significantly contributing to the largest increase in the ohmic resistance observed in this case.

Kurşun zirkonat titanat (PZT) bazlı ferroelektrik seramik malzemeler ticari öneme sahip piezoelektrik malzemelerdir. Stronsiyum zirkonat titanat (SZT) perovskit malzemeleri de geniş bir uygulama alanına sahiptir. PZT ve SZT başlangıç çözeltileri uygun olan çeşitli yöntemler kullanılarak hazırlanabilir. Bu yöntemler arasında sol-jel işlemi, düşük sıcaklık gereksinimi, homojenlik ve uygun partikül boyutunun elde edilebilmesi nedeniyle özel ilgi görmüştür. Elektroeğirme yöntemi nanofiber üretiminde en etkin ve en yaygın kullanılan yöntemdir. Elektroeğirme, katı ve boşluklu içyapılı, uzun boylarda, homojen çapta ve çeşitli bileşimlerde nanofiber üretimi sağlayan bir yöntemdir. Elektroeğirme teknolojisi sol-jel yöntemi ile birleştirildiğinde, polimer veya seramik çözeltiden belirli bir elektrik alan altında sürekli nanofiber, nanotüp ve dolgulu nanofiber üretimi gerçekleşmektedir.Bu çalışmada, Sr ve Pb içeren kurşun zirkonat titanat (PZT) ve stronsiyum zirkonat titanat (SZT) çözeltileri sol-jel yöntemi ile hazırlanmıştır. Çözeltiler, öncü malzemeler olarak metal tuzları ve alkoksitler kullanılarak hazırlanmıştır. Elde edilmiş olan Çözeltiler, 1.6, 1.8, 2.0 mL / saat akış hızlarında beslenmiştir ve 20 kV voltaj değerinde PZT ve SZT nanofiberleri elektrospinning yöntemi ile oluşturulmuştur. Elektroeğirme cihazının farklı parametreleri incelenmiş ve SZT ve PZT nanofiberleri optimum özelliklerde üretilmiştir. Üretilen nanofiberlerin kristal yapısı, morfolojik yüzey karakterizasyonu ve kimyasal özellikleri sırasıyla XRD, SEM ve EDX ile yapılmıştır. XRD sonuçları Sol-jel ve elektrospinning işlemleri sırasında PZT ve SZT'nin perovskit yapısının bozulmadığını göstermiştir. PZT ve SZT nanofiberlerin SEM analizlerinde az miktarda boncuksu yapı gözlemlenmiştir. Nanofiberlerin EDX analizine göre PZT ve SZT yapısının da oluştuğu görülmüştür., Lead zirconate titanate (PZT)-based ferroelectric ceramic materials are piezoelectric materials of commercial importance. Strontium zirconate titanate (SZT) perovskite materials also have a wide application area. PZ and SZT starting solutions can be prepared using a variety of suitable methods. Among these methods, the sol-gel process has attracted special attention due to the low temperature requirement, homogeneity and the ability to obtain the appropriate particle size. The electrospinning method is the most effective and widely used method in nanofiber production. Electro-spinning is a method that enables the production of solid and hollow nanofibers in long lengths, homogeneous diameters and various compositions. When the electro-spinning technology is combined with the sol-gel method, continuous nanofibers, nanotubes and filled nanofibers are produced from polymer or ceramic solution under a certain electric field.In this study, lead zirconate titanate (PZT) and strontium zirconate titanate (SZT) solutions containing Sr and Pb were prepared by sol-gel method. Solutions were prepared using metal salts and alkoxides as the precursor materials. The solutions obtained were fed at flow rates of 1.6, 1.8, 2.0 mL / hour and PZT and SZT nanofibers were formed by electrospinning method at 20 kV voltage rating. Different parameters of the electrospinning device were examined and the SZT and PZT nanofibers were produced with optimum properties. Crystal structure, characterization of morphological surface and chemical properties of the produced nanofibers were done with XRD, SEM and EDX, respectively. XRD results showed that the perovskite structure of PZT and SZT was not damaged during Sol-gel and electrospinning processes. A small amount of beady structure was observed in SEM analysis of PZT and SZT nanofibers. According to EDX analysis of nanofibers, it was observed that the PZT and SZT structure was also formed.

International audience; Enhancement of lead zirconate (PbZrO 3) polarization is achieved by using a titanium seed layer on alumina polycrystalline substrate. Thanks to the reduction of the lattice mismatch between the platinum electrode (3.92 Å) and the PbZrO 3 films (4.14 Å), lead zirconate thin films oriented along the (111) direction with an orientation factor of around 65 % has been obtained. The (111) PbZrO 3 presents an increase of 56 % of the polarization compared to the (100) PbZrO 3. This enhancement is responsible of the higher recoverable energy storage density obtained in the (111) PbZrO 3 thin films (8 J/cm 3 at 600 kV/cm with an efficiency of 72 %). The (111) PbZrO 3 also has a higher figure of merit, which indicates that the (111) crystallographic plane is the most favorable direction for energy storage.

Rare earth zirconate pyrochlore compounds with their unique crystal structure have been extensively used as thermal barrier coatings, ionic conductors and buffer layer for high-temperature coated conductors. In this work, Y2(Zr1-xTix)2O7 (YZTO) thin films, as one kind of rare earth zirconates doped with Ti4+ ions, were employed to investigate the structural phase transition and its effect on oxygen diffusion in YZTO thin films. YZTO thin films were prepared on single-crystal silicon substrates by sol–gel method with adding a certain amount of Ti4+ ions into Y2Zr2O7 precursor solution. It was found that the crystal structure of YZTO thin films started gradually to transform from defective fluorite structure with disordered oxygen vacancies to pyrochlore structure with highly ordered oxygen vacancies as the doping ratio of Ti4+ ions was increased. Remarkably, in YZTO thin films, the higher the doping ratios of Ti4+ ions are, the stronger the ability to block oxygen diffusion will become.

The aim of this work is to develop an effective catalyst for the conversion of butanediols, which is derivable from biomass, to valuable chemicals such as unsaturated alcohols. The dehydration of 1,4-, 1,3-, and 2,3-butanediol to form unsaturated alcohols such as 3-buten-1-ol, 2-buten-1-ol, and 3-buten-2-ol was studied in a vapor-phase flow reactor over sixteen rare earth zirconate catalysts at 325 &deg, C. Rare earth zirconates with high crystallinity and high specific surface area were prepared in a hydrothermal treatment of co-precipitated hydroxide. Zirconates with heavy rare earth metals, especially Y2Zr2O7 with an oxygen-defected fluorite structure, showed high catalytic performance of selective dehydration of 1,4-butanediol to 3-buten-1-ol and also of 1,3-butanediol to form 3-buten-2-ol and 2-buten-1-ol, while the zirconate catalysts were less active in the dehydration of 2,3-butanediol. The calcination of Y2Zr2O7 significantly affected the catalytic activity of the dehydration of 1,4-butanediol: a calcination temperature of Y2Zr2O7 at 900 &deg, C or higher was efficient for selective formation of unsaturated alcohols. Y2Zr2O7 with high crystallinity exhibits the highest productivity of 3-buten-1-ol from 1,4-butanediol at 325 &deg, C.

International audience; In antiferroelectric PbZrO 3 thin films, a weak residual ferroelectric phase is often observed on the double hysteresis loop and it is important to know its impact on the dielectric properties. To study this residual phase, a low and homogeneous electric field can be used because antiferroelectric domain walls are not sensitive to homogeneous fields; thus, contributions of ferroelectric domain wall motions to permittivity and dielectric losses can be isolated. In this paper, the hyperbolic law characterization is used on lead zirconate thin films, which present a residual ferroelectric phase. The study shows that domain wall contributions of the ferroelectric phase are small (less than 2% of the total permittivity), but their impacts are very important in the overall dielectric losses (%26%). These losses are, however, lower than those obtained in pure ferroelectric materials due to a residual state composed of well distributed ferroelectric clusters of small size with no interactions between domain walls.

Various types of fuels were used in a low-temperature solution combustion synthesis of zinc zirconate nanocomposite at a pH of 7. In the synthesis, the fuels used were citric acid, glycine, urea, hydrazine hydrate, and ammonium nitrate while zirconium butoxide and zinc nitrate were the precursor sources of Zr4+ and Zn2+ ions, respectively. The samples were calcined for 2 h at a temperature of 600 °C. The study of the structural properties showed varied morphologies ranging from highly agglomerated surfaces, crystalline aggregates as well as nanorods. There was a gradual growth of zinc zirconate perovskite within phases of zirconia and zinc oxide. It was observed that there were prominent photoluminescence emissions spread from violet-blue into the yellow-white regions with peaks varying from about 400 to 490 nm. The energy bandgap of the nanocomposites was between 2.93 and 3.22 eV depending on the fuel used in the preparation of the sample.

Strontium zirconate (SrZrO3) commercial powder was plasma sprayed using a high-feedrate water-stabilized plasma system (WSP) torch. Coatings with a thickness of about 1 mm were produced. Now, we are concentrating on a topic never addressed for pure SrZrO3 coatings: how the coatings interact with natural dust, known as calcium-magnesium-aluminum-silicate (CMAS). We selected various regimes of thermal treatment where SrZrO3 coatings were exposed to CMAS, and studied chemical changes, phase changes and the microstructure evolution of the influenced coatings. Microhardness of the exposed coatings was monitored as well. The results would help to understand, how the excellent refractory material SrZrO3 interacts with natural silicates. We kept in mind that pure SrZrO3 is not optimal for a thermal barrier application because of high-temperature phase transformations, but to study the CMAS-induced phenomena in more complex compositions, for example La2Zr2O7-SrZrO3, is difficult and interpretations have not been completed currently. The value of the actual research is in the separation of the phenomena typical just for SrZrO3. A potential for newly developed phases to serve as a sacrificial components of various barrier-coating systems is discussed. Several physical aspects of the newly developed components are discussed as well, namely the luminescence. Here the dust-based phases shifted down the temperature at which luminescence can occur in pure SrZrO3 ceramics. The entire thickness of influenced layers was relatively high, around 300 &micro, m. The amorphous component, predominant after short-term CMAS exposure, was subsequently crystallized to various phases, namely SrSiO3 and monoclinic as well as tetragonal zirconia.

Ti–Zr alloys are expected to be novel biomaterials with low stress shielding owing to their lower Young’s moduli than pure Ti. The drawback of metallic biomaterials is that their bone-bonding abilities are relatively low. NaOH and heat treatments have been performed to provide Ti–50Zr with apatite-forming ability in the body environment, which is essential for bone bonding. However, the systematic compositional dependence of apatite formation has not been revealed. In the present study, NaOH treatment of Ti–Zr alloys with various compositions and bone-bonding abilities was assessed in vitro by apatite formation in simulated body fluid (SBF). The corrosion current density in NaOH aqueous solution and the amount of Na incorporated into the surface tended to decrease with increasing Zr content. The apatite-forming ability of the treated alloy significantly decreased when the Zr content was ≥60 atom%. This phenomenon is attributed to the (1) low OH content on the surface, (2) low Na incorporation into the treated alloy surface, which enhances apatite formation, and (3) low ability of P adsorption to the Ti–Zr alloy in SBF following Ca adsorption to trigger apatite nucleation. Although the adhesion of the titanate/zirconate layer formed on the surfaces to the substrates increased as Zr content increased, the adhesion between the apatite and the substrate was still low.