Search

This paper thoroughly examines lanthanum-doped lead titanate (PbLaxTi(1−0.75x)O3), a perovskite-based ceramic material, focusing on its structural properties, vibrational behavior, and radiation shielding capabilities. Using advanced techniques like X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM), we explore the intricate relationship between lanthanum doping levels and material properties. Additionally, we assess its radiation shielding potential through metrics. Computational approaches employing the FLUKA code help evaluate theoretical values. Our findings reveal that increasing lanthanum concentration alters crystal atom arrangement, influences vibrational patterns, and enhances radiation shielding effectiveness. Increasing lanthanum concentration resulted in a maximum 7.55% rise in the mass attenuation coefficient (MAC) at 0.059 MeV. The half-value layer (HVL) decreased by 4.68% at 1.33 MeV, and the mean free path (MFP) decreased by 5.78% at 1.41 MeV with increased lanthanum ratio. Moreover, the radiation protection efficiency (RPE) increased from 30.7779 to 32.67442% at 0.059 MeV as lanthanum content increased. These findings offer valuable insights into material characteristics and suggest potential applications in enhancing radiation shielding for medical and industrial purposes. This comprehensive analysis provides practical insights for potential applications, particularly in medical or industrial radiation protection. The data-driven approach here paves the way for future research at the intersection of data science and material science, advancing material design and understanding doped perovskite materials. [ABSTRACT FROM AUTHOR]

Gd ion-substituted barium bismuth titanate (BaBi4Ti4O15; BBTO) Aurivillius ceramics were synthesized to understand the preliminary impact through the structural, optical, frequency-dependent dielectric, conductivity, and complex modulus spectroscopic studies. X-ray diffraction (XRD) study confirmed the phase purity and crystallinity of the orthorhombic crystal system with A21am space group. The room temperature Raman study was correlated with the XRD results revealing a more feasible Aurivillius phase. A shift in the Curie temperature (Tm) towards low-temperature regions with increasing concentrations of Gd dopant was observed in temperature-dependent conductivity studies. The frequency-dependent conductivity study revealed a diffuse relaxor signature that degraded with dopant concentration explained by the modified Curie–Weiss law and normalized dielectric permittivity study. The frequency and temperature dependent modulus spectroscopic study indicated a dielectric relaxation mechanism in the presence of doubly ionized oxygen vacancies in pristine BBTO ceramics whereas the dominance of singly ionized oxygen vacancies was observed in Gd-doped one. The dielectric relaxation mechanism for pristine and doped Aurivillius are explained due to the thermal motion of the localized hopping process of electrons in variable oxidation states of different single ionized ions that depart from ideal Debye behavior. A detailed ac-conductivity study revealed the jumping relaxation mechanism or correlated barrier hopping mechanism (CBM) because of the localization of charge carriers, or the formation of polarons, respectively. [ABSTRACT FROM AUTHOR]

Calcium titanate powder CaTiO3 was subjected to heat treatment and utilized to fabricate hybrid nanocomposite films of polyvinyl alcohol (PVA)/graphite nanoflakes by solution casting technique. The effects of various content of graphite (0, 4, and 8 wt%) on the crystal microstructure, optical parameters, and dielectric behavior of the PVA containing 4wt% of CaTiO3 were investigated. The X-ray diffraction analysis showed a heat treatment of CaTiO3 increased the crystal size and lattice strain. The addition of graphite into the PVA containing heat-treated CaTiO3 weakened the intensity of the main diffraction peaks in PVA films, indicating the drop of crystallinity. The optical absorption spectrum revealed a greater value of optical absorption and index of refraction for the PVA blend containing thermal-treated CaTiO3 than untreated CaTiO3. The incorporation of thermal-treated calcium titanate with graphite dropped the optical energy gap of PVA from 6.4 to 5.2 eV. That was followed by a subsequent increment in the value of Urbach energy in the prepared composite films. Dielectric characterizations showed the addition of heat-treated calcium titanate with graphite improved the low-frequency dielectric constant of the polymer and enhanced the ac conductivity by up to seven orders of magnitude. The increase of ac conductivity was found to be consistent with the rise in the value of loss tangent in the nanocomposite. [ABSTRACT FROM AUTHOR]

Metal–insulator–metal (MIM) devices were fabricated with Al/Al2TiO5 stack on Pt/Ti coated SiO2/Si substrates and studied the effect of synthesized oxygen flow rate on their composition, structural and electrical properties. X-ray photoelectron spectroscopy revealed that the presence of aluminum, titanium and oxygen with the ratio 2:1:5, respectively in the projected mixed insulator Al2TiO5. XRD spectra showed that the Al2TiO5 high-k films were amorphous in nature. The average grain size observed from atomic force micrograph of the deposited high-k layer could be 25 nm. The capacitance–voltage curves showed reasonably accepted accumulation capacitance values. The films showed the dielectric constant of 19.3 and the leakage current density of 4 × 10–7 A/cm2 with good break down behavior. The leakage current in the films can be attributed to the Fowler–Nordheim mechanism due to tunneling of electron at higher electric field and Poole–Frenkel emission in the medium field region since the dielectric films contained the defects and traps. [ABSTRACT FROM AUTHOR]

In this study, the temperature sensing behaviors of emissions of Stark sublevels in Er3+/Yb3+ codoped lead lanthanum zirconate titanate (PLZT) transparent ceramic were examined. Based on the temperature-dependent upconversion fluorescence spectra excited by 980 nm, the emission intensities of the Stark sublevels 2H11/2(1, 2), 4S3/2(1, 2), and 4F9/2(1, 2, 3) were obtained upon increasing the temperature from 160 to 320 K. All the transitions present strong temperature dependence under the competitive effects of thermal excitation and nonradiative relaxation. The optical temperature sensing properties of 2H11/2/4S3/2(1), 2H11/2/4S3/2(2), 2H11/2/4F9/2(1), 2H11/2/4F9/2(2), and 2H11/2/4F9/2(3) were investigated using the fluorescence intensity ratio (FIR) technique. The largest absolute sensitivity Sa of 142.4 × 10–4 K−1 was obtained based on the FIRs of 2H11/2/4F9/2(1) at 320 K, which is approximately 26 times larger than that of traditionally used thermal coupled levels 2H11/2/4S3/2 in the considered sample. In contrast, the maximum relative sensitivity Sr was 2.21% K−1 at 203 K. A comparison of these results with those of other Er3+/Yb3+ codoped materials reveals that Er3+/Yb3+: PLZT ceramics are a promising thermometer material at low temperatures. Applying FIRs based on the photoluminescence of Stark sublevels is a practical approach to achieving greater thermometric efficiency. [ABSTRACT FROM AUTHOR]

In this work, silica-modified titanate nanotubes (TNTs-SiO2) were prepared via a hydrothermal process using tetraethylorthosilicate (TEOS) and anatase TiO2 as precursors. A design of experiments (DOE) using a two-level fractional factorial design was applied to study the effect of the TiO2/TEOS molar ratio, reaction temperature and time on the Brunauer–Emmett–Teller (BET) specific surface area (Y) of TNTs-SiO2, the objective being to maximize Y (Ymax). Our results show that the BET specific surface area is highly affected by the TEOS amount and by the reaction temperature, the highest value being 312.735 m2/g with a pore volume of 0.91 cm3/g which corresponds to the TNTs-SiO2 07 sample. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images show the formation of TNTs with a length of several hundred nanometers and 8 and 10 nm in internal and external diameter, respectively, after 6 h of reaction at 150 °C. According to Fourier transform infrared (FT-IR) and energy-dispersive X-ray spectroscopy (EDX) analyses, Si is well incorporated into the TNTs. The TNTs-SiO2 07 sample was applied as an adsorbent of Pb(II) and Cd(II) ions. The response surface methodology (RSM) via Box–Behnken design (BBD) was used to optimize the removal efficiency of Pb(II) (RPb%) and of Cd(II) (RCd%) and to study the influence of the initial metal concentration, of the adsorbent mass and of the pH on the responses. The Pb(II) and Cd(II) removals follow the Freundlich model (R2 = 0.999 and 0.996, respectively) and pseudo-second-order kinetics (R2 = 0.9). The maximum adsorption capacity was estimated to be 689.655 mg/g for Pb(II) and 338.983 mg/g for Cd(II). This article highlights the significant improvement in the structural properties of TNTs-SiO2 and their adsorption efficiency of Pb(II) and Cd(II) ions. [ABSTRACT FROM AUTHOR]

BaZrxTi(1 − x)O3 powders were solid-state synthesized from mixtures of BaCO3 and ZrO2 powders of micron sizes and TiO2 nanopowder at a concentration of substituting zirconium atoms of 10–50 wt%. The dependencies of the grain-size distribution and phase composition, diffuse reflection spectra in the UV, visible, near IR, and IR regions, as well as the solar absorptance (as), on zirconium atom concentration were studied. It was stated that the maximal yield of the main phase of the powder was 88.5%. The high reflective capacity in the visible region of the spectrum and the low value of the solar absorptance as is determined by the presence of unreacted TiO2 nanoparticles in a quantity of up to 7.3% in the phase composition and small sizes of grains and granules of the powder. [ABSTRACT FROM AUTHOR]

Cr-doped and undoped lithium zinc titanate (LZTO), Li2ZnCrxTi3−xO8 (x = 0, 0.1, 0.3, 0.5) has been prepared as alternative anode using a simple and facile high-temperature solid-state ball-milling route followed by calcination in the air atmosphere. The cubic spinel structure with P4332 space group is confirmed through X-ray Diffraction (XRD) for all compositions indicating doping of Cr3+ does not cause any changes within the lattice as well as maintain the phase structure up to an optimized doping. The study of morphology and distribution of the particles in the synthesized LZTO and doped LZTO compositions are carried out via scanning electron microscopy and transmission electron microscopy (TEM). It reveals the formation of polyhedron-shaped spherical facets in the sub-micron to nanometer range as observed by TEM. The particle size reduces toward the nanometer range as the amount of Cr doping increases and it also decreases the agglomeration of particles. All the samples doped with Cr indicate good electrochemical performance as compared to pristine LZTO. Sample Li2ZnCr0.3Ti2.7O8 doped with Cr content 0.3 displays higher discharge capacity, better cyclability, and lower polarization among all other Cr doped samples. Li2ZnCr0.3Ti2.7O8 delivered excellent rate performances attaining capacities of 251.73 ± 4, 184.34 ± 5, 157.42 ± 5, and 119.03 ± 4 mAh g−1 at 0.1C, 0.5C, 1, and 2C, respectively, which is higher than the pristine LZTO sample. Electrochemical impedance spectroscopy shows Li2ZnCr0.3Ti2.7O8 acquired a lower value of charge-transfer resistance and the fastest Li-ion diffusivity which enhances its capacity at higher current rates and makes it suitable as an alternative anode for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

Ferroelectric materials with the typical perovskite structure are widely used in capacitors, ultrasonic devices, oil drilling, transducers, and other fields. Lead-lanthanum-zirconium-titanate ceramics co-doped with Sn and Ba, have been widely investigated. However, there is little attention has been focused on the dielectric properties of barium-lanthanum-zirconium-titanate. Thus, in this work, Sn doped Ba0.955La0.03Zr0.02Ti0.98O3 ferroelectric ceramics were prepared via a classical high-temperature solid state reaction. Scanning Electron Microscopy (SEM) was used to observe the surface appearance of ceramics. The X-ray diffraction (XRD) patterns at room temperature, indicate that the ceramics are well crystallized. Impedance properties and dielectric properties reflect the characteristic of typical high temperature dielectric relaxation behavior. The conductive activation energy and the relaxation activation energy are obtained through the calculation of the Arrhenius law. The fitting results show that the dielectric relaxation behavior at high-temperature, was related to the oxygen defect. The electrical modulus verified the partial short-range carrier migration, also contribute to the high-temperature dielectric properties. [ABSTRACT FROM AUTHOR]

Ceramic samples of lead zirconate titanate doped with lanthanum at the morphotropic phase boundary (PLZT 1.0/53/47) exhibit ferroelastic phase transition in the range from 135 to 150 °C. The study used structural analysis (XRD and Raman spectroscopy) and variation of dielectric and piezoelectric characteristics with temperature to analyze the ferroelastic and ferroelectric phase transition in PLZT. Measurements of X-ray diffraction patterns with temperature in the range from room temperature to 500 °C made it possible to monitor the evolution of the crystalline phases present in the sample, with a mixture of rhombohedral and tetragonal phases and initial concentrations of approximately 40 and 60%, respectively, as well as the evolution of the cell parameters and crystallite size. All techniques applied in this study showed the presence of phase changes in the temperature range from 135 to 150 °C, which is attributed to a displacive proper ferroelastic phase transition. This transition is associated with a decrease in the concentration of the rhombohedral phase and an increase in that of the tetragonal phase. Additionally, a transition at 350 °C is observed, which corresponds to the ferroelectric-paraelectric phase transition, coinciding with the results reported by Morgan Electro Ceramics for Type II Marine ceramics (PZT-5A). [ABSTRACT FROM AUTHOR]

Ceramic samples of lead zirconate titanate doped with lanthanum at the morphotropic phase boundary (PLZT 1.0/53/47) exhibit ferroelastic phase transition in the range from 135 to 150 °C. The study used structural analysis (XRD and Raman spectroscopy) and variation of dielectric and piezoelectric characteristics with temperature to analyze the ferroelastic and ferroelectric phase transition in PLZT. Measurements of X-ray diffraction patterns with temperature in the range from room temperature to 500 °C made it possible to monitor the evolution of the crystalline phases present in the sample, with a mixture of rhombohedral and tetragonal phases and initial concentrations of approximately 40 and 60%, respectively, as well as the evolution of the cell parameters and crystallite size. All techniques applied in this study showed the presence of phase changes in the temperature range from 135 to 150 °C, which is attributed to a displacive proper ferroelastic phase transition. This transition is associated with a decrease in the concentration of the rhombohedral phase and an increase in that of the tetragonal phase. Additionally, a transition at 350 °C is observed, which corresponds to the ferroelectric-paraelectric phase transition, coinciding with the results reported by Morgan Electro Ceramics for Type II Marine ceramics (PZT-5A). [ABSTRACT FROM AUTHOR]

Rare-earth Nd-doped lead zinc niobate-lead titanate (Nd:PZN-PT) and W-doped lead zinc niobate-lead titanate (W:PZN-PT) single crystals have been grown by self-flux technique and their dielectric, ferroelectric and piezoelectric properties have been investigated. Pure perovskite phases were observed, and lattice parameters were obtained by Rietveld refinement. Diffuse phase transition and frequency dispersive phenomena was observed in the dielectric peaks confirming the enhancement of relaxor behaviour for doped crystals. Variation of dielectric constant (ε), AC conductivity and piezoelectric charge coefficient (d33) as a result of doping is investigated in detail. From the hysteresis behaviour, it was evident that a simple domain switching mechanism was observed for doped crystals. [ABSTRACT FROM AUTHOR]

Ultrasound provided a good dispersion of CuS on TiONTs. In order to prepare CuS/TiONTs with a good heterostructure, the CuS particles must establish contact with TiONTs uniformly. The hydrothermal process was divided into two phases, and different times of ultrasound were introduced before each stage. The effects of ultrasonic-assisted hydrothermal method on the structure and photoelectric properties of CuS/TiONTs were investigated by SEM, XRD, photocurrent, and degradation of MB. The results show that the introduction of ultrasound before the hydrothermal treatment can cause damage to the TiONTs. However, the ultrasound between the two hydrothermal stages makes CuS distributed in the TiONTs uniformly, and the amount of CuS can be increased. The photocurrent reaches 32 mA/cm at 1.5 V, and meanwhile the photocatalytic activity under visible light is also improved. [ABSTRACT FROM AUTHOR]

The pure and Er, Ti co-doped BiFeO thin films were prepared by chemistry solution deposition. Enhanced ferroelectric and ferromagnetic properties were obtained, which is mainly attributed to that the effect of co-doping Er and Ti leads to the drastic crystal structural transformation from rhombohedral phase to orthorhombic phase. Thus crystal structural transformation not only changes the switching behavior of the polarization path to improve the ferroelectric polarization, but also suppresses the original spiral spin structure to release the locked magnetization. At the same time, the leakage current density is decreased after doping Er and Ti, which results from that the crystal structural transformation changes the leakage current mechanism. The present work provides an available way on improving the multiferroic properties of BiFeO thin films. [ABSTRACT FROM AUTHOR]

CaCuTiO powder has been synthesized by mechanochemical milling (C-m) and solid-state reaction (C-ssr) techniques. C-m powder has a grain size of ~24 nm as determined from X-ray diffraction and FE-SEM measurements. The grain size of C-m ceramics has increased to 20 μm compared to a size of 3 μm for C-ssr ceramics after sintering at 1,050 °C for 10 h. Giant dielectric constant was observed in both ceramics with that of C-m larger than that of C-ssr. Impedance results show that the grain conductivity of C-m is more than two orders of magnitude lower than that of C-ssr, whereas its grain boundary conductivity is larger than that of C-ssr. These results are supported by the EDX results that show Cu-enriched grain boundaries in C-m ceramics. [ABSTRACT FROM AUTHOR]

We investigated the twin domain distribution and lattice parameter variations associated with the displacive phase transition in SrTiO by means of X-ray diffraction with high spatial resolution. By using 4.5-keV photons, the probed region is the first micrometer near the surface. We find a very inhomogeneous domain distribution, showing both regions with large monodomains and highly twinned regions, as well as large needle domains. Also, the lattice parameters in these different regions vary substantially. [ABSTRACT FROM AUTHOR]

Wurtzite ( w) and zincblende ( zb) InN films have been grown on (011) SrTiO (STO) substrates by metal-organic chemical vapor deposition, the epitaxial relationships and optical properties are characterized by X-ray diffraction (XRD), absorption and photoluminescence (PL). Based on XRD θ-2 θ and Φ scanning results, the epitaxial relationships between ( w- and zb-) InN films and STO substrates are determined, that is, (0001)[11 20]//(011)[100] and $(100)[011]_{\mathit{zb}\mbox{-}\mathrm{InN}}//(011)[100]_{\mathrm{STO}}$. Compared with the w-InN films, the zb-InN films exhibit a red shift in absorption edge and PL spectra, and a much narrower and stronger PL spectrum, implying a better optical quality of zb-InN films. The structure transition is supposed to be due to the difference in atom and bond areal density between the crystal plane of w-InN(0001) and zb-InN(100). [ABSTRACT FROM AUTHOR]

A heterojunction was fabricated by growing a layer of BiSrCoO thin film on the 0.7 wt% Nb-doped SrTiO substrate. Such heterojunction showed good rectifying characteristics over a wide temperature range, and its transport mechanism under the forward bias can be attributed to a space charge limited conduction mechanism via defects near the interface of the heterojunction. Photovoltaic properties of the heterojunction were studied by using both continuous-wave and pulsed irradiations and the results can be well explained by the photovoltaic effect of a p-n junction. [ABSTRACT FROM AUTHOR]

Electrical properties of SrTiO single crystal samples treated by an anisotropic surface annealing technique under reducing conditions have been investigated in the temperature range of 35 K-300 K. Optical and atomic force microscopy show that annealing gives rise to polycrystallization and the formation of colored dendritic structures. Carrier concentrations and mobilities determined by Hall measurements as well as resistivities detected by van der Pauw measurements show the expected metallic behavior due to oxygen vacancy doping. Moreover, the temperature dependent resistivities indicate a cubic-to-tetragonal phase transition, which to our knowledge has not been reported before. Additionally, the transition occurred up to 53 K above the known bulk transition temperature T at 105 K with a hysteresis up to a temperature of 220 K. Both phenomena possibly arise from dislocations and associated strain fields introduced by surface annealing that are assumed to lower the free energy of the tetragonal phase and simultaneously pin tetragonal domains. Thus, microregions of the tetragonal phase persist above T causing the hysteresis in resistivity up to ∼12%. This effect possibly provides new chances for future oxide based non-volatile data-storage devices. [ABSTRACT FROM AUTHOR]

Thin films of bismuth titanate BiTiO and different sodium-bismuth-titanate phases NaBiTiO, NaBiTiO, and NaBiTiO with different numbers of perovskite units ( m) between two BiO intermediate layers were epitaxially grown on (001) SrTiO substrates by metal-organic chemical vapor deposition. The optical properties of these ferroelectric thin films were investigated by spectroscopic ellipsometry (SE) at room temperature in the 0.73-6.48 eV spectral range. In the analysis of the SE measured spectra Cauchy transparent, Tauc-Lorentz and Gaussian dispersion relations were used to characterize the optical properties of the films. Our analysis clearly shows that the refractive index of the Aurivillius phases decreases with increasing m, while the optical band gap increases with increasing m. The obtained dielectric function spectra revealed a shoulder and a broad absorption band at about 3.7 and 4.5 eV, respectively, for BiTiO and a broad absorption band around 4.5 eV for the perovskite phase NaBiTiO. A shift in the resonance energies to lower energy with increasing m is observed. [ABSTRACT FROM AUTHOR]

In the present work, (1− x)(0.935BiNaTiO-0.065BaTiO)- xKNbO (BNT-BT-KN, BNT-BT-100 xKN) ceramics with x ranging from 0 to 0.1 were prepared by the conventional ceramic fabrication process. A large electrostrictive coefficient of ∼10 m C is obtained with the composition x ranging from 0.02 to 0.1, which is close to the well-known electrostrictive material Pb(MgNb)O. Under an electric field of 4 kV/mm, the electrostrictive strain can reach as high as 0.08%. Besides, the electric field induced strain behavior indicates a temperature independent behavior within the temperature range of 20 to 150°C. The large electrostrictive strain is suggested to be ascribed to the formation of non-polar (NP) phase developed by the KNbO substitution, and the high electrostrictive coefficient of BNT-BT-KN ceramics makes them great candidates to be applied in the new solid-state actuators. [ABSTRACT FROM AUTHOR]

New perovskite solid solution ceramics of (1− x)BaTiO- xBi(MgTi)O ((1− x)BT- xBMT, x≤0.09) were synthesized by the solid-state reaction technique. X-ray diffraction studies have revealed a stable single perovskite structure for all samples. Dielectric measurements were carried out at different frequencies and temperatures. The polarization evolutions with temperatures were measured to investigate the ferroelectric properties. All the compositions show features of ferroelectrics with diffuse phase transition, though the temperature T of their dielectric constant maximum ε is frequency dependent. The dielectric constant peak ε( T) of (1− x)BT- xBMT ceramics become broad with increasing BMT content. During the temperature range of ε( T) peak summit, (1− x)BT- xBMT ceramics present quasi-linear dielectric phenomenon under high electric field with very high dielectric constant. [ABSTRACT FROM AUTHOR]

The large band gap (3.58 eV) and dielectric properties ( ε=50) of bulk SrHfTiO (SHTO) make it a promising high- k material. SHTO films were deposited on p-type (100) Si single crystal substrates by pulsed laser deposition. The composition, structure, thickness, and roughness of the SHTO films have been studied using X-ray Photoelectron Spectroscopy, X-ray reflectivity, transmission electron microscopy, and atomic force microscopy. The capacitance-voltage and leakage current density characteristics of the films have been evaluated. For a post-annealed SHTO film with a thickness of 25 nm, the relatively high permittivity of 35 was achieved with the low leakage current density of 4.96×10 A/cm at −2 V bias voltage. [ABSTRACT FROM AUTHOR]

We report here the formation of single phase lead zirconate titanate (PZT) nanopowder with composition Pb(ZrTi)O and average crystallite size 12-20 nm, synthesized by sol-gel process. The phase evolution of PZT gel powder, heat treated at temperatures 550, 650 and 800°C was monitored by X-ray diffraction (XRD) and X-ray photo-electron spectroscopy (XPS). The high resolution XPS spectra of Pb4f, Zr3d, Ti2p and O1s show that PZT with pure perovskite structure is obtained at 800°C while at lower temperatures pyrochlore phase co-exists with perovskite phase. The XRD results also support this analysis. We have also identified the pyrochlore phase using XPS by analyzing the corresponding variations in the FWHM values, peak positions and the separation between the spin doublets of Pb, Zr and Ti associated with it. The composition of the final powder obtained with pure perovskite structure is calculated and is close to the designed value. [ABSTRACT FROM AUTHOR]

Upconversion (UC) emission properties of Yb, Er co-doped lead lanthanum titanate inverse opal photonic crystals were investigated. The results showed that the photonic band gap has a significant influence on the upconversion emission of Yb, Er co-doped lead lanthanum titanate inverse opal photonic crystals. Significant suppression of the upconversion emission was detected if the photonic band gap overlapped with the Er ions emission band. [ABSTRACT FROM AUTHOR]

Structural changes in commercial lead zirconate titanate (PZT) ceramics (EC-65) under the application of electric fields and mechanical stress were measured using neutron diffraction instruments at the Australian Nuclear Science and Technology Organisation (ANSTO) and the Oak Ridge National Laboratory (ORNL). The structural changes during electric-field application were measured on the WOMBAT beamline at ANSTO and include non-180° domain switching, lattice strains and field-induced phase transformations. Using time-resolved data acquisition capabilities, lattice strains were measured under cyclic electric fields at times as short as 30 μs. Structural changes including the (002) and (200) lattice strains and non-180° domain switching were measured during uniaxial mechanical compression on the NRSF2 instrument at ORNL. Contraction of the crystallographic polarization axis, (002), and reorientation of non-180° domains occur at lowest stresses, followed by (200) elastic strains at higher stresses. [ABSTRACT FROM AUTHOR]

A hydrothermal treatment of titanium dioxide (TiO2) with various bases (i.e., LiOH, NaOH, KOH, and NH4OH) was used to prepare materials with unique morphologies, relatively small crystallite sizes, and large specific surface areas. The experimental results show that the formation of TiO2 is largely dependent on the type, strength and concentration of a base. The effect of the nature of the base used and the concentration of the base on the formation of nanostructures were investigated using X-ray diffraction, Raman spectroscopy, transmission and scanning electron microscopy, as well as surface area measurements. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) were both used to transform the morphology of starting TiO2 material. [ABSTRACT FROM AUTHOR]

This paper focuses on the deposition and electromechanical characterization of lanthanum-doped lead hafnate titanate (PLHT) thin films as key material in piezoelectric microelectromechanical systems (pMEMS). PLHT ( x/30/70) and PLHT( x/45/55) films with a thickness between 150 nm and 250 nm were deposited by chemical solution deposition (CSD). Thereby x varies between 0 and 10% La content. The electrical characterization shows that undoped ( x=0) PLHT exhibit ferroelectric behavior similar to PZT of the same composition. La doping results in reduced ferroelectric properties and also affects the electromechanical properties. Measurements using a double beam laser interferometer yield a piezoelectric coefficient d33 of 60 pm/V, which stays constant with an increasing electric field. This leads to a linear displacement compared to undoped PLHT or conventional PZT films used for MEMS applications. [ABSTRACT FROM AUTHOR]

Ca0.997Pr0.002TiO3 (CPTO) thin films that show strong red luminescence were successfully prepared by means of an excimer laser assisted metal organic deposition (ELAMOD) process with a KrF laser at a fluence of 100 mJ/cm2, a pulse duration of 26 ns, and a repetition rate of 20 Hz at 100°C in air. The CPTO films grew on the silica, borosilicate, and indium-tin-oxide (ITO) glasses. The crystallinity of the CPTO films depended on the substrates; the films were well grown on the borosilicate and ITO glasses compared to the silica glass. To elucidate the key factors for the crystallization of the CPTO films in this process, we carried out numerical simulations for the temperature variation at the laser irradiation, using a heat diffusion equation, and compared the experimental data with thermal simulations. According to the results, we have shown that a large optical absorbance of the film and a small thermal conductivity of the substrate provide effective annealing time and temperature for the crystallization of the CPTO films, and polycrystalline intermediate layer which has a large optical absorption such as the ITO also plays a key role for the nucleation of the CPTO crystals in the ELAMOD process. [ABSTRACT FROM AUTHOR]

The patterning of lanthanum-doped lead zirconate titanate (PLZT) and strontium-doped lead zirconate titanate (PSZT) thin films has been examined using a 5-ns pulsed excimer laser. Both types of film were deposited by rf magnetron sputtering with in situ heating and a controlled cooling rate in order to obtain the perovskite-structured films. The depth of laser ablation in both PSZT and PLZT films showed a logarithmic dependence on fluence. The ablation rate of PLZT films was slightly higher than that of PSZT films over the range of fluence (10–150 J/cm2) and increased linearly with number of pulses. The threshold fluence required to initiate ablation was ∼ 1.25 J/cm2 for PLZT and ∼ 1.87 J/cm2 for PSZT films. Individual squares were patterned with areas ranging from 10×10 μm2 up to 30×30 μm2 using single and multiple pulses. The morphology of the etched surfaces comprised globules which had diameters of 200–250 nm in PLZT and 1400 nm in PSZT films. The diameter of the globules has been shown to increase with fluence until reaching an approximately constant size at ≤ 20 J/cm2 in both types of film. The composition of the films following ablation has been compared using X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. [ABSTRACT FROM AUTHOR]

The effect of Zr content on the crystal structure and electrical properties of barium zirconate titanate (Ba(Zr,Ti)O3) was studied by X-ray diffraction and dielectric, ferroelectric and impedance spectroscopy. An increase of Zr content into BaTiO3 leads to a reduction in its c-parameter and an increase in its a-parameter, resulting in a change from tetragonal to cubic symmetry of the BaTiO3 unit cell. The Curie temperatures are lowered and the relative permittivity values are decreased with increasing Zr content. The presence of BaZrO3 secondary phases has the affect of decreasing tanδ. A higher applied electric field is required during the polarization process because of the effect of domain-wall pinning caused by oxygen vacancies. Impedance spectroscopy studies of Ba(Ti0.95Zr0.05)O3 ceramics show a decrease in the bulk resistance with increasing temperature, indicating a typical negative temperature coefficient of resistance. [ABSTRACT FROM AUTHOR]

Co-doped titanate nanotubes were prepared from hydrothermal treatment on Co-doped anatase TiO2 powders in a concentrated NaOH aqueous solution and characterized by a variety of techniques. We mainly investigated the structural and magnetic properties of these nanotubes. It was found that the obtained nanotubes might possibly be constructed from H2Ti3O7, their undoped counterpart. The result from Raman spectra showed that Ti–OH bonds existed in the tubular structure. The electron paramagnetic resonance and X-ray photoelectron spectroscopy studies clearly showed that the Co was incorporated into the titanate lattice as Co2+ and substituted for Ti cations sites. Also, from the photoluminescence measurement, the presence of oxygen vacancies was detected in the nanotubes. The vibrating sample magnetometer measurement revealed a clear paramagnetic behavior with weakly ferromagnetic ordering at room temperature. The results suggested that ferromagnetism of the nanotubes was related to the oxygen vacancies and could be suppressed by their quantum size. [ABSTRACT FROM AUTHOR]

Sodium bismuth titanate (NBT) based ceramics have been shown to be a promising lead-free alternative to commercial piezoelectrics and high capacitance materials. This article reports a novel aqueous citrate gel route for the synthesis of (Na0.5Bi0.5)xBa1-xTiyZr1-yO3 powders. Instead of alkoxides, usually used in citrate gel route, aqueous citrate solutions of titanium and bismuth were prepared from their respective inorganic salts. These solutions were used to prepare powder of (Na0.5Bi0.5)0.88Ba0.12Ti0.96Zr0.04O3. The process produced an amorphous xerogel that was readily crystallized to a pseudocubic perovskite phase when calcined at temperatures as low as 500 °C. The decomposition and oxidation of the xerogel was studied using TG-DTA, which showed complete removal of volatile components by 580 °C. The formation of crystalline phases was studied using XRD. SEM was used to evaluate the sintering behavior of the powder. The powder exhibits significant sintering at temperatures 800–900 °C. The polarization behavior of the sintered material was similar to one prepared by conventional solid state route. A maximum polarization of ∼24 μC/cm2 and peak bipolar strain ∼0.095% at 44 kV/cm was achieved in the sintered material. [ABSTRACT FROM AUTHOR]

Lead titanate ceramics have been prepared by two different processing methods: conventional (or single-stage) and two-stage sintering. Effects of designed sintering conditions on phase formation, densification, microstructure and dielectric properties of the ceramics were characterized via X-ray diffraction, Archimedes density measurement, scanning electron microscopy and dielectric measurement, respectively. The potentiality of a two-stage sintering technique as a simple ceramic fabrication method to obtain highly dense and pure lead titanate ceramics was demonstrated. It has been found that, under suitable two-stage sintering conditions, dense perovskite lead titanate ceramics can be successfully achieved with better dielectric properties than those of ceramics from a single-stage sintering technique. [ABSTRACT FROM AUTHOR]

Lead lanthanum zirconate titanate (PLZT 9/65/35) thin films were deposited on MgO (00l) substrates using a sol–gel method. X-ray diffraction measurements reveal that the PLZT film has epitaxially grown on the substrate and has a pure perovskite structure. Using gold interdigital electrodes the in-plane dielectric properties of the films were measured as a function of frequency (1 kHz to 10 GHz), temperature (293–435 K) and dc electric field (0–20 MV/m). The PLZT (9/65/35) thin film exhibits a diffuse phase transition, which indicates a relaxor-like ferroelectric behavior. The temperature dependence of the characteristic relaxation time was analyzed in terms of the Vögel–Fulcher relation. The relative permittivity has a high tunability of 34–42% in the frequency range of 10 MHz to 1 GHz. [ABSTRACT FROM AUTHOR]

Lead zirconate titanate (PZT) fibres were prepared by a powder-based extrusion method. Pre-sintered PZT powder mixed with poly(acrylic acid) was spun in a spinnerette to produce fibres. The fibre of ∼400 μm diameter was used to fabricate 1-3 PZT fibre/epoxy composite discs with different volume fractions (ϕ) of PZT. Since the ceramic fibres are rather brittle, their elastic properties cannot be measured directly. In order to determine the properties of the ceramic fibres, effective properties of the fibres/epoxy 1-3 composite were measured. By using a modified series and parallel model, the properties of 1-3 composites can be calculated. Then, the elastic coefficient s33,fibreE, relative permittivity ε33,fibreT and piezoelectric strain coefficient d33,fibre of the ceramic fibre could be found. Ring-shaped PZT fibre/epoxy materials composites with different ϕ were fabricated to be used as the sensing material in force sensor applications. The ring-shape composite with ϕ=0.5 was installed into a housing and the sensor was calibrated by different methods and its sensitivity was found to be 144 pC/N within the frequency range of 0.5–6.4 kHz which is much higher than that of a quartz force sensor with a similar structure. [ABSTRACT FROM AUTHOR]

There is an increasing interest in lead-zirconate-titanate (PZT) based ferroelectric thin film and devices in recent years. Pulsed laser deposition (PLD) technique has been demonstrated to be a versatile and successful tool for the deposition of epitaxial multi-component metal oxide films and heterostructures. This review presents a reasonable understanding of the relationship between PLD processing and composition, crystal structure and orientation of PZT ferroelectric thin films, and heterostructures. Processing-related issues from PLD of PZT thin films and material-integration strategies developed to fabrication of highly oriented or epitaxial PZT thin film based capacitors with excellent ferroelectric properties are discussed in detail. [ABSTRACT FROM AUTHOR]

Lanthanum-substituted bismuth titanate (Bi3.25La0.75Ti3O12) (BLT) thin films were deposited on p-type Si(100) substrates using a chemical solution deposition process. The ferroelectric and dielectric properties of the films with an Au/BLT/Si structure were investigated. It was found that retention behaviors of the capacitors after polling with a negative and positive voltage were very different. The capacitor at an accumulation state exhibited a better retention characteristic than that at a depletion state. A rapid loss of memory for the capacitor at depletion state was found and attributed to the depolarization fields inside the ferroelectric film. It is proposed that the interaction between injected charges and ferroelectric polarization plays a role in the retention properties of the MFS capacitors. [ABSTRACT FROM AUTHOR]

It is experimentally known that a polymer matrix phase in a composite of ferroelectric particles dispersed in a ferroelectric polymer can be polarized by using a few cycles of an ac field, without causing much disturbance to the state of polarization of the inclusion particles. This paper attempts to investigate this special poling process for a typical ferroelectric composite system of lead zirconate titanate (PZT) ceramic particles in a vinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) copolymer matrix, upon the application of 10 Hz ac fields of various amplitudes. Compared to a copolymer sample, the composite samples can be polarized at a lower field, and hence show a larger “remanent” polarization at the same poling field. Among the composites, the observed “remanent” polarization increases with increasing ceramic volume fraction. These experimental observations can be understood by a simple model, in which space charges are allowed to accumulate at the particle-matrix interfaces because of the electrical conductivity of the constituents. At a fast switching poling field of 10 Hz, the calculation shows that conductivity and charge accumulation effects in the composite are only minimal. Accordingly, although the PZT phase as well as the copolymer phase are both polarized under the ac field, the ceramic phase is only polarized to about 10% when the copolymer phase is almost fully polarized. Thus, one can still use an ac field to polarize only the copolymer phase of the composite without altering the polarization state of the ceramic phase significantly. [ABSTRACT FROM AUTHOR]

Barium-modified bismuth sodium titanate, 0.94 ×(Bi0.5Na0.5)TiO3-0.06BaTiO3 (BNBT-6), fine-scale piezoelectric fibres were fabricated using a viscous suspension spinning process (VSSP). The sintered BNBT-6 fibres with diameters of ~300 µm were fabricated into 1-3 composites with fibre volume fraction vf of 0.2-0.5. Piezoelectric and dielectric properties of the 1-3 composites were measured. The electromechanical coupling coefficient kt of a vf=0.40 composite is 0.52. Properties of the VSSP fibres were calculated using the measured properties of the 1-3 composites. A vf=0.40 composite was thinned down to ~213-µm thickness and constructed into an ultrasonic transducer. The pulse-echo response, bandwidth and insertion loss of the transducers were studied. The VSSP fibre composite transducer with vf=0.40 has a centre frequency of ~7 MHz with a bandwidth of 88%. The good performance indicated that the BNBT-6/epoxy 1-3 fibre composite transducer has potential for medical imaging applications. [ABSTRACT FROM AUTHOR]

Strontium-modified lead titanate (PST) thin films with composition Pb1-xSrxTiO3 (0.10

Highly (100)-oriented, compositionally graded (Pb,Ca)TiO[sub 3] (PCT) thin films with a Ca content from 0 to 24 mol % on Pt/Ti/SiO[sub 2]/Si substrates were prepared by a sol-gel process. The graded structure of the Au/PCT/Pt film capacitor showed a well-saturated hysteresis loop at an applied field of 500 kV/cm with remanent polarization (P[sub r]), and coercive electric field (E[sub c]) values of 9.35 μC/cm[sup 2] and 130 kV/cm, respectively. At 100 kHz, the dielectric constant and dielectric loss of the film were 129 and 0.024, respectively. The leakage current density of the graded PCT film was less than 1.0×10[sup -7] A/cm[sup 2] over a voltage range from 0 to 4 V. The conduction current depended on the voltage polarity. At low electric field (110 and 180 kV/cm, respectively, for Pt and Au electrodes biased negatively), the Au/PCT and PCT/Pt interfaces form a Schottky barrier. At high electric field (>110 kV/cm), the Au electrode biased negatively shows space-charge-limited current (SCLC) behavior. The temperature dependencies of the pyroelectric coefficients of the graded PCT film were measured by a dynamic technique. From 20 to 82 °C, the pyroelectric coefficients of graded PCT film remain steady in the range 106 to 118 μC/m[sup 2] K. The detectivity figure of merit (F[sub D]) of the graded PCT film was 6.7×10[sup -6] Pa[sup -0.5]. [ABSTRACT FROM AUTHOR]

Fine titanate nanowires of K[sub 2]Ti[sub 8]O[sub 17] structure with a diameter of 5–10 nm and a typical length of several micrometers to several tens of micrometers have been synthesized hydrothermally via a reaction of titania particles and KOH solution. The growth of nanowires is along the [010] direction. The surface area of nanowires can exceed more than 300 m[sup 2]/g, which is expected to be significant in their applications to catalysis and other fields. Calcination over 600 °C causes K[sub 2]Ti[sub 8]O[sub 17] nanowires to decompose to K[sub 2]Ti[sub 6]O[sub 13] and TiO[sub 2]. [ABSTRACT FROM AUTHOR]

Pb[sub 1-x]Mg[sub x]TiO[sub 3] (PMT) thin films (x=0–0.08) were deposited onto Pt/SiO[sub 2]/Si substrates by diol-based sol-gel processing. The influence of various processing methods on the characteristics of the thin films was studied by varying the magnesium contents and heating temperatures (500–800 °C) of the samples. In the present study, the relative dielectric constant (ε[sub r]) of the PMT thin films increased from 25.8 to 91.8 as the magnesium content increased. The coercive field (E[sub c]) and the remanent polarization (P[sub r]) decreased as the magnesium content increased, but the dielectric loss factor (cosδ) and the pyroelectric coefficient (p) increased. The PMT thin films with x=0.06 exhibited the largest figures of merit for voltage responsivity and specific detectivity. These results indicate that the PMT thin film with x=0.06 was most suitable for application to high-performance pyroelectric thin-film detectors. [ABSTRACT FROM AUTHOR]

In this work we report the synthesis of nanocomposites based on nanoparticles of cobalt titanate and titanium dioxide in their anatase crystalline phase by a sol–gel process. The synthesized nanoparticles of titanate vary from 1 to 6 nm in size. They are embedded in the anatase matrix, and they were obtained from TiO[sub 2] monoliths doped with Co[sup 2+]. The formation of cobalt titanate nanoparticles showed a linear dependence on the cobalt concentration. The cobalt titanate nanocrystals are very stable even at temperatures higher than 1000 °C. The crystalline structures of the samples were examined using high-resolution transmission electron microscopy and X-ray diffraction. Molecular simulation methods were utilized for a better understanding and for improving the analytical data interpretation of the experimental results. [ABSTRACT FROM AUTHOR]

Photoluminescence at room temperature was observed in amorphous zirconium titanate obtained from the polymeric precursor method. This was the first time in which PL was noticed in an amorphous compound made of two network formers. The PL spectra could be deconvoluted into two bands, whose center 1 was located from 540 nm to 552 nm and center 2 from 625 nm to 641 nm. The co-existence of fivefold and sixfold oxygen coordination of titanium and/or zirconium could be the origin of the radiative recombination of electron-hole pairs in amorphous ZT, which may be responsible for the emission of the photoluminescence. [ABSTRACT FROM AUTHOR]

UV laser (λ=355 nm) ablation of piezoelectric lead zirconate titanate (PZT) ceramics in air has been investigated under different laser parameters. It has been found that there is a critical pulse number (N=750). When the pulse number is smaller than the critical value, the ablation rate decreases with increasing pulse number. Beyond the critical value, the ablation rate becomes constant. The ablation rate and concentrations of O, Zr and Ti on the ablated surface increase with the laser fluence, while the Pb concentration decreases due to the selective evaporation of PbO. The loss of the Pb results in the formation of a metastable pyrochlore phase. ZrO[sub 2] was detected by XPS in the ablated zone. Also, the concentrations of the pyrochlore phase and ZrO[sub 2] increase with increasing laser fluence. These results clearly indicate that the chemical composition and phase structure in the ablated zone strongly depend on the laser fluence. The piezoelectric properties of the cut PZT ceramic samples completely disappear due to the loss of the Pb and the existence of the pyrochlore phase. After these samples were annealed at 1150 °C for 1 h in a PbO-controlled atmosphere, their phase structure and piezoelectric properties were recovered again. Finally, 1–3 and concentric-ring 2–2 PZT/epoxy composites were fabricated by UV laser micromachining and their thickness modes were measured by impedance spectrum analysis and a d[sub 33] meter. Both composites show high piezoelectric properties. [ABSTRACT FROM AUTHOR]

We discuss the nature of visible photoluminescence at room temperature in amorphous strontium titanate in the light of the results of a recent experimental and quantum mechanical theoretical study. Our calculation of the electronic structure involves the use of first-principles molecular calculations to simulate the variation of the electronic structure in the strontium titanate crystalline phase, which is known to have a direct band gap, and we also make an in-depth examination of amorphous strontium titanate. The results of our simulations of amorphous strontium titanate indicate that the formation of five-fold coordination in the amorphous system may introduce delocalized electronic levels in the highest occupied molecular orbital and the lowest unoccupied molecular orbital. These delocalized electronic levels are ascribed to the formation of a tail in the absorbance-spectrum curve. Optical absorption measurements experimentally showed the presence of a tail. The results are interpreted by the nature of these exponential optical edges and tails associated with defects promoted by the disordered structure of the amorphous material. We associate them with localized states in the band gap. [ABSTRACT FROM AUTHOR]

The elemental composition and the surface morphology of thin films grown by laser ablation of barium titanate with femtosecond pulses at 620 nm laser wavelength have been systematically studied according to the experimental pulsedlaser deposition parameters: laser energy density, oxygen pressure, substrate temperature, target-substrate distance and substrate position (in- and off-axis geometry). Firstly, even at high temperature (700 °C), the deposits consist of coalesced particles up to 1-μm in size, mixed in a poorly crystallised tetragonal BaTiO[sub 3] thin film. The particles formed in femtosecond pulsed-laser deposition induce a high surface roughness, which is observed whatever the experimental growth conditions and does not correspond to the droplets often observed during laser ablation in the nanosecond regime. As shown by plasma expansion dynamics, these particles propagate toward the substrate in the plasma plume with a low velocity, and are assumed to be produced by gas-phase reactions. Moreover, the cationic concentration evaluated through the Ba/Ti ratio strongly depends on the oxygen pressure in the ablation chamber and the angular position of the substrate along the normal to the target at laser impact. Indeed, the films appear to be enriched in the heavy element (Ba) when the substrate is located at high angular deviation. This fact is correlated to an increase in the lighter species (i.e. Ti) in the central part of the plasma plume. [ABSTRACT FROM AUTHOR]

Raman spectroscopy was used to investigate the lattice dynamics and structural transformations in bismuth titanate (Bi[sub 4] Ti[sub 3] O[sub 12] ) nanocrystals prepared by a chemical coprecipitation technique. The crystal structure of the samples of different grain sizes was determined by X-ray-diffraction analysis. The evolution of the Raman spectrum with grain size was characterized by an intensity decrease, a broadening of the line width, a frequency shift, and the disappearance of the Raman mode. The results revealed the appearance of a size-driven phase transition from orthorhombic to tetragonal phases at a critical size of 44 nm. This result is quite consistent with the X-ray-diffraction measurement and differential thermal analysis. The origin was attributed to the grain-size effect and explained by the surface-energy mechanism. [ABSTRACT FROM AUTHOR]