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The thermal and radiation stabilities of the formulations based on ethylene–propylene–diene rubber (EPDM), which contain barium titanate (BaTiO3) doped with lanthanum and cerium oxides, were investigated by chemiluminescence and mechanical testing. The contributions of these doped fillers are related to the surface interaction between the structural defects (doping atoms, i.e., lanthanum and cerium) implanted in the filler lattice and the molecular fragments formed during the progress of degradation. These composite materials present extended durabilities with respect to the references; the oxidation periods are a minimum of three times longer than the corresponding times for pristine polymers. This behavior is associated with the scavenging activity of dopants. Mechanical testing has demonstrated the contributions of doped filler to the improvement of tensile strength and elongation at break by the restructuration of the polymer phase. Scanning electron microscopy images revealed the densification of materials in the presence of doped barium titanates. All the investigations constitute valid proof for the qualification of BaTiO3 doped with Ce as the more efficient stabilizer compared to the same inorganic filler doped with La. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics, most commonly prepared via conventional process based on a solid-state synthesis, can be used as acoustical transducers or sensors in many application fields. Particularly in some applications where specific geometries are desirable, the need of complex, time consuming, and costly operations could make conventional process inappropriate. This paper proposes an alternative solution based on additive manufacturing (AM), which is of great interest to control and shape the structure in an automatic manner. A formulation of ceramic slurry, consisting of 80%wt doped barium titanate (BT) and organic mixture, was investigated. The synthesized slurry is revealed to be compatible with the robocasting technique while maintaining good mechanical strength after debinding and sintering steps. Empirical measures together with microscopic analysis confirm high densities of the printed BT ceramics (∼ 95% after sintering), which is consistent to those obtained in literatures. To better assess the material and process performances, microstructural, dielectric and piezoelectric characterizations are conducted on both 3D printed and conventional BT ceramics. The results demonstrate that the printed samples give rise to excellent dielectric and piezoelectric properties (d 33 coefficient of 260 pC/N and dielectric constant of 1800), which are very close to the values obtained by conventional method on the same composition. As only a few and recent works have been found in the literatures on such systems, this study highlights the considerable and growing potential of robocasting techniques in the field of piezoelectric ceramics. The obtained d 33 coefficient is revealed as the highest value reported for printed BT doped systems. [Display omitted] [ABSTRACT FROM AUTHOR]

This study presents the functional effects of doped BaTiO 3 powders loaded in ethylene-propylene elastomers (copolymer – EPR and terpolymer – EPDM) investigated by chemiluminescence (CL). The presence of foreign atoms (lanthanum and cerium) in the barium titanate lattice produces an improved activity on the stabilization of polymer matrices. The concentration of filler was 1 wt%, where the doping atoms behave as the trapping radicals assuring the increase of the low onset oxidation temperatures for pristine material (168 °C for EPDM and 175 °C for EPR) to higher values for BaTiO 3 /La (183 °C for EPDM and 189 °C for EPR) and BaTiO 3 /La (190 °C for EPDM and 195 °C for EPR) after receiving 25 kGy. The isothermal determinations point out the protection efficiency proved by the lower positions of the recorded CL spectra for composites in respect with pristine polymers. The compared protection activities at 100 kGy exhibited by the studied composites highlight the greater contribution of BaTiO 3 /Ce than BaTiO 3 /La indicating the dependence of stabilization effectiveness on the nature of dopant. The present results state the structural influence of backbone configuration on the filler effects on the amelioration of thermal and radiation strengths. • The doped barium titanate presents stabilization activity in SEBS matrix. • Cerium atoms have stronger effect than lanthanum atoms in BaTiO 3 nanoparticles. • Under γ-irradiation up to100 kGy the tested doped barium titanate is still active. • The studied stabilization activity may be extended to other polymeric structures. • The protection contribution of doped BaTiO 3 recommend them for nuclear applications. [ABSTRACT FROM AUTHOR]

Barium titanate (BaTiO3) is being studied extensively to replace lead-based piezoelectric materials, such as the lead zirconate titanate (PZT) family, due to lead toxicity. As a result, researchers are turning to materials such as BaTiO3 and seek to improve their properties with the use of dopants. In many applications such as Tonpilz transducers, piezoelectric materials undergo mechanical stress which is important to control and predict their electro-acoustic performance. Thus, this study deals with a fully tensorial model that allows us to simulate the behaviors of electrical displacements and elastic strains under mechanical stress. The simulated curves are compared with the experimental ones obtained for a doped BaTiO3 composition and the hysteretic curves of strains are in good agreement both for the unpoled and poled samples. The values and global behavior of the theoretical electrical displacement are also found to be in fair agreement, though some discrepancies are observed. The optimized values of the physical parameters, such as $d_{33}$ , are discussed and improvements both of the model and the optimization procedure are finally proposed to better predict the mechanical behavior of the doped BaTiO3 piezoceramics. [ABSTRACT FROM AUTHOR]

Plasma-enhanced atomic layer deposition (PEALD) of ultrathin (∼7 nm) slightly Ti-rich Ba x Ti y O z (BTO) films with different Al-doping concentration ([Al]/([Al] + [Ba] + [Ti]) = 0 to 22 at%) was studied. In particular, the effects of Al-doping in BTO on compositional, crystallographic and electrical properties were investigated. Previously, BTO films with a Ti cation composition, [Ti]/([Ba] + [Ti]) = ∼60 at% was reported to be advantageous for crystallization, resulting in superior dielectric properties. These Ti-rich BTO films, however, suffered from high leakage currents, necessitating the change in its crystalline structure as well as elemental composition. By incorporating Al 2 O 3 into the BTO films, the leakage current can be controlled, where the BTO films with an Al-doping concentration of 12 at% showed a leakage current reduced by one order of magnitude compared to un-doped BTO (i.e., ∼10 −7 to ∼10 −6 A/cm 2 at +1.6 V) without a significant drop of the dielectric constant (43,un-doped to 40, Al-doped). [ABSTRACT FROM AUTHOR]

Barium titanate is one of the most thoroughly studied members of the perovskite family due to its prominent place in the electroceramic industry. To be used as a capacitor at room temperature, a high-dielectric constant is needed which is achieved through doping. The focus of this research was to develop a more environmentally benign alternative to the doping of barium titanate. The barium source was barium titanyl catecholate, Ba[Ti(cat)3] (aq) and the doping sources were strontium oxalate (SrC2O4) and strontium carbonate (SrCO3). The doping strategies included a solid-state synthetic pathway as well as microwave- and centrifuge-assisted methods which both employed water as the only solvent. The last two benign by design methods were tested with respect to their thermodynamic control over barium-to-strontium stoichiometric ratios. These methods of doping proved to be more environmentally friendly and economical while combining green chemistry and materials science. [ABSTRACT FROM AUTHOR]

Niobium doped barium titanate was prepared using two procedures. First, doped barium titanate was prepared starting from citrate solutions of all components and second, pure barium titanate powder was obtained from the citrate solutions and after that doped. Besides niobium, a small amount of manganese, as acceptor dopant was added. Phase composition, crystal structure, microstructure and dielectric properties were reported. The influence of powder processing on the properties of niobium doped barium titanate was analysed. The grain growth and the concentration of dopants on the dielectric properties were considered. [ABSTRACT FROM AUTHOR]

Abstract: Renewed interest in the perovskite ferroelectric barium titanate (BaTiO3) has been driven by the introduction of large recoverable electrostrain in doped BaTiO3-based materials. Our previous work demonstrated that the potential for high-performance in Pb-free ferroelectrics based on BaTiO3 was confirmed in Fe3+/Nb5+-doped BaTiO3 systems. It is well documented that the electronic behavior of BaTiO3 is intimately related to the chemical state of the constituents. However, information regarding the chemical states of the ions of the Fe3+/Nb5+-doped BaTiO3 ceramics is currently unavailable. Consequently, this study describes the chemical state of sintered hybrid Fe3+/Nb5+-doped BaTiO3 ceramics, compared with undoped BaTiO3 ceramics derived from the same processing. Analysis by X-ray photoelectron spectroscopy (XPS) showed that the binding energy of Ti indicates the presence of more than one component of Ti within the doped BaTiO3 ceramics, but only one component of Ti within the undoped BaTiO3 ceramics. Unlike Ti, the XPS spectra indicates that more than one type of barium and oxygen species exist in both undoped and doped BaTiO3 ceramics. [Copyright &y& Elsevier]