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BaTiO3 nanopowders doped with La and co-doped with La/Mn were prepared by auto-combustion and Pechini methods, respectively. The influence of the synthesis methods, dopants and sintering temperature on the BaTiO3 structure and its potential to be used as humidity and/or H2 gas sensor were studied. The optimization of all process parameters was perf...
Citations
... Due to the smaller radius of La 3+ (1.36 Å) in comparison with Ba 2+ (1.6 Å), the occupancy of lanthanum at the A-site of the lattice creates a reduction in cell volume [20]. The doping mechanism of lanthanum can take place via two mechanisms; an electronic La-donor doping mechanism which involves the generation of electrons or an ionic partial replacement mechanism involving the creation of titanium vacancies [21]. Over the years, the latter mechanism has been verified to be the most favorable way in which the doping process occurs. ...
Volatile organic compounds pose an acute threat to the environment and human life. Formaldehyde, a well-known volatile organic compound known for its numerous commercial applications, has put forth the requirement for tracking down trace amounts of its presence in order to ensure healthier living. This work emphasizes the novel use of a non-toxic deep eutectic solvent medium (choline chloride and urea) for aiding the solid-state synthesis of pure and La-doped barium titanate. The prepared chemiresistive ceramics were verified for their gas sensing abilities towards a number of volatile organics, among which formaldehyde (100 ppm) showed amplified response of 118 in La-doped BTO modified gold interdigitated electrode. It also produced a rapid response-recovery rate of 12 sec/18 sec witnessing the extreme performance of La-doped BTO ceramic material. Additionally, the chemiresistive sensor was stable to humidity and had extended-shelf life.
... They have also reported that the incorporation of smaller rare-earth ions like Nd 3 + (1.27 Å) and La 3 + (1.36 Å) into Ba 2+ (1.61 Å) ions enhances the dielectric properties thereby stabilizing the tetragonal phase [17,18]. In addition to this, the doping concentration of these rare earth doping can modify the behavior to a semi-conducting type before arriving at the critical concentration and thereafter become an insulator after attaining the critical concentration [19]. Among the various possible rare-earth dopants, Lanthanum (La) is a key material of great significance [20][21][22]. ...
The present manuscript outlines the investigation of the structure, dielectric and optical properties of Lanthanum (La) doped BaTiO3 (BLT) ceramic with compositions of Ba1-xLa2x/3TiO3 prepared by the solid-state reaction method. The Rietveld refinement of the XRD pattern illustrates that La doping changes from tetragonal structure to cubic structure with a mixed phase in intermediate composition. The Raman spectra illustrate the existence of modes associated with tetragonal symmetry up to x = 0.05 and the disappearance of modes at 307 cm−1 confirming the cubic symmetry for higher doping concentration. The temperature variant dielectric study in the studied range reveals a two-phase transition until x = 0.05 which merges for higher concentrations. The temperature variant dielectric study expresses that the transition temperature declines whereas the dielectric constant at transition temperature increases as a function of doping content. The dielectric loss of the doped samples is found to increase until x = 0.05 and thereby decreases for higher concentration values. The temperature coefficient of the dielectric constant was calculated for all the compositions. The diffusivity was calculated using the altered Curie–Wiess law revealing that the diffusivity increases because of doping percentages. A signature of relaxor nature is obtained in the composition x = 0.1, which is confirmed by the Vogel–Fulcher (VF) fitting. The optical property of all the prepared samples has been studied using UV–Vis spectroscopy and photoluminescence.
... Moreover, many studies have reported the potential of cubic BaTiO 3 in sensor applications. According to Petrovic et al., pseudocubic La-doped BaTiO 3 shows greater performance in gas sensing than that the tetragonal phase [39]. Chaudhari et al. reported the potential of nanocubic BaTiO 3 in the detection of liquid petroleum gas [40]. ...
Although barium titanate (BaTiO3) shows prominent dielectric properties for fabricating electronic devices, its utilization in electrochemical applications is limited. Thus, this study examined the potential of a BaTiO3-based composite in the detection of a food additive, i.e., citric acid. First, a submicron-scale BaTiO3 powder was synthesized using the solution combustion method. Then, a BaTiO3/multiwalled carbon nanotube (MWCNT) composite was hydrothermally synthesized at BaTiO3:MWCNT mass ratios of 1:1 and 2:1. This composite was used as a working electrode in a nonenzymatic sensor to evaluate its electrocatalytic activity. Cyclic voltammetric measurements revealed that the BaTiO3/MWCNT composite (2:1) exhibited the highest electrocatalytic activity. Reduction reactions were observed at applied voltages of approximately 0.02 and −0.67 V, whereas oxidation reactions were detected at −0.65 and 0.47 V. With acceptable sensitivity, decent selectivity, and fair stability, the BaTiO3/MWCNT composite (2:1) showed good potential for citric acid detection.
... By slight doping of barium titanate, lattice can be deformed and tetragonal structure can change into the pseudo-cubic. 10,11 Using the standard Scherer equation, the particle size was determined at about 25 nm. The X-ray diffraction patterns further confirm the presence of both ferrite phases. ...
Owing to high dielectric constants and coupled magnetic properties at room temperature, multiferroics related materials have wide application in many fields like multi-layer ferroic capacitors and multifunctional devices. Nickel ferrite, barium titanate composite is prepared from co-precipitation method and sintered at high temperature (1273 K). Intrinsic stretching vibrations observed in FTIR spectra at 594 cm⁻¹. X-ray measurements detected the presence of their single phases (tetragonal perovskite crystal). Variations of AC dielectric constant in these samples have been studied. The influence of the phase content on the dielectric constant and loss tangent conductivity was also studied. The AC measurement yields smaller variations at a low range of frequency and more variations in higher frequency ranges indicate amplification of confined states with the availability of large charge carriers. A magnetic measurement reveals that the soft ferromagnetic properties of 68.356 emu g⁻¹ and 20.465 emu g⁻¹ at room temperature.
... ferroelectric ceramics have attracted increasing attention for various reasons, such as their ability to be prepared as thick films without cracking because of mechanical stress relaxation, [10][11][12] the tunability of their microstructure and ferroelectric properties, [13][14][15][16] their ability to be prepared as nanostructured objects via a self-assembly process, [17][18][19] and their usefulness in the study of fundamental physical phenomena in ferroelectrics with defects. 5,7,[20][21][22] Increasing film thickness due to mechanical stress relaxation in porous film is important for piezoelectric microelectromechanical systems (MEMS) applications because the output signal is increased by increasing the film thickness and the electromechanical response is enhanced by local elastic relaxations, 12,[23][24][25] decreasing permittivity can provide a better figure of merit for pyroelectric detectors, 16,26 the self-assembly of nanodots arrays can be used in memory technology, 17,18 porous ferroelectric films can be used to create gas sensors, [27][28][29] and different composite structures in which a porous ferroelectric material is filled with another material. [30][31][32][33] Porous structures in ferroelectric films can be achieved using sol-gel techniques. ...
Porous ferroelectric lead zirconate–titanate (PZT) films with different internal structures are synthesized using a sol–gel technique and spin‐on deposition on platinized silicon substrates. The films’ porosity is engineered using various structure‐directing agents: polyvinylpyrrolidone with a molecular weight of 360 000 (1–6.6 wt.%) and block copolymer surfactants Brij 30 and Brij 76 (30–60 wt.%). The films’ structures are characterized by transmission electron microscopy. The PVP‐based films contain large, elongated pores with diameters as large as 100 nm. By contrast, the films prepared from solutions with block copolymers exhibit a small pore size depending on the surfactant molecular weight (10–19 nm for Brij 30 and 20–27 nm for Brij 76), with a mostly uniform distribution of channel‐like pores within the film volume. Despite their highly porous structures, all of the films show a columnar‐grain perovskite structure with grains as large as several micrometers and curved grain boundaries. The films demonstrate ferroelectric behavior with dielectric hysteresis, and their permittivity decreases with increasing porosity. Thus, the Brij 30 and Brij 76 copolymer surfactants can be used to engineer fine porous structures in PZT films for various applications in electronics.
... In addition, the reaction of the chemisorbed oxygen ions species (O -, O 2-) on the nano-surface is accompanied with liberate of electrons to the conduction band which leads to the observed change in conductance increases (Fig. 2a). The same process has been demonstrated in some sample [33]. ...
The perovskite sample La 0.7 Sr 0.25 Na 0.05 Mn 0.7 Ti 0.3 O 3 (LSNM 0.70 T 0.30) was produced via a solid-state route process. The frequency dependence of electrical conduction plot established that according to the Jonscher law. The electrical conduction process was based on both theoretical conduction models assigned to the non-overlapping small polaron tunneling model at low temperatures and correlated barrier hopping mechanism at high temperatures. Detailed investigation of impedance data revealed a non-Debye-type relaxation occurring in the polycrystalline. In addition, the dielectric response confirmed the dominance of the Maxwell-Wagner model and Koop's phenomenological theory effect in conduction phenomenon. The values of permittivity is high for LSNM 0.70 T 0.30 were observed. These values make this composition interesting for microelectric applications. In the thermal study, the relaxation processes observed by electrical conductivity, impedance, and modulus are associated with singly and doubly ionized oxygen vacancies for the lower and higher temperature, respectively.
... In addition, the reaction of the chemisorbed oxygen ions species (O -, O 2-) on the nano-surface is accompanied with liberate of electrons to the conduction band which leads to the observed change in conductance increases (Fig. 2a). The same process has been demonstrated in some sample [33]. ...
The perovskite sample La0.7Sr0.25Na0.05Mn0.7Ti0.3O3 (LSNM0.70T0.30) was produced via a solid-state route process. The frequency dependence of electrical conduction plot established that according to the Jonscher law. The electrical conduction process was based on both theoretical conduction models assigned to the Non-overlapping Small Polaron Tunneling model at low temperatures and Correlated Barrier Hopping mechanism at high temperatures. Detailed investigation of impedance data revealed a non-Debye-type relaxation occurring in the polycrystalline. In addition, the dielectric response confirmed the dominance of the Maxwell-Wagner model and Koop’s phenomenological theory effect in conduction phenomenon. The value of permittivity is highly for LSNM0.70T0.30 were observed. These values make this composition interesting for microelectric applications. In the thermal study, the relaxation processes observed by electrical conductivity, impedance, and modulus are associated with singly and doubly ionized oxygen vacancies for the lower and higher temperature, respectively.
... BT posses high permittivity, low dielectric losses and high tunability and was promoted as a material for the high speed and nonvolatile memory devices [13,14]. It is well known that dielectric properties of barium titanate can be significantly modified by doping with La 3+ , Mn 3+ , Zr 3+ , Hf 4+ , Nb 5+ , where the characteristic phase transition can be shifted to lower temperatures and doping can lead to the appearance of semiconductivity in the material [15,16]. Ba(Ti y Zr 1-y )O 3 (BTZr) is derived from two perovskite lattices, barium titanate and barium zirconate. ...
... The increase of grain size can enhance the domain switching ability and enable the improvement of the ferroelectric properties, P r and P s . Also, high number of grain boundaries in the ceramics with small grains can result with decrease of P r and P s , since the grain boundaries posses low permittivity and poor ferroelectricity and can affect greatly the reduction of polarization [15,49]. It is difficult to say which ferrite phase has the greatest impact on ferroelectric properties because none of the material did not reach the saturation. ...
Multiferroic composites with general formula Ba(Ti0.95Zr0.05)O3 – Ni0.7Zn0.3Fe2O4, Ba(Ti0.95Zr0.05)O3 – CoFe2O4, Ba(Ti0.95Zr0.05)O3 – Ni0.7Cu0.01Sm0.05Zn0.29Fe1.95O4, (BTZr(95–5) – NZF, BTZr(95–5) – CF, BTZr(95–5) – NCuSmZF) were prepared by mixing chemically obtained different types of ferrites and BTZ(95–5) powders in the planetary mill for 24 h. The optimization of sintering process was performed and powders were pressed and sintered at 1300 °C for obtained composites samples. From the X-ray analysis for single phase and composites ceramics the formation of crystallized structure of ferrites and barium zirconium titanate can be noticed. SEM analyses indicated the formation of two types nanosized grains, polygonal ferromagnetic and rounded ferroelectric grains. The electrical properties of these materials were investigated using impedance spectroscopy and analysis of ferroelectric measurements. Impedance analysis of all investigated samples has shown different relaxation processes that originated from the grain and grain boundary contributions. The results of polarization vs. electric field measurements have shown the influence of magnetic phase type and its concentration on the ferroelectric properties of the composites. Due to high conductivity of ferrite phases and presence of interfacial polarization, the shapes of these curves differed from the conventional ferroelectric materials.
... Titanates are a group of inorganic compounds composed of titanium, oxygen, and one or more other metallic elements and have been widely used in the fields of photocatalysis [1], sensors [2], reinforcement materials [3], ion-exchange agent [4,5], etc., because of their high dielectric constant, good insulation, optical properties, piezoelectric properties, and thermoelectric properties. Titanate whiskers are well known as structural reinforcing materials for metal and polymer ceramic composites due to their excellent mechanical properties and thermal stability [6,7]. ...
K2MgTi7O16@K0.8Mg0.4Ti1.6O4(PMTC) core–shell composite whiskers and TiO2 (TO) whiskers have been obtained from potassium magnesium titanate whisker (K0.8Mg0.4Ti1.6O4, KMTO) by a first different degree ion-controlled exchange reaction and a subsequent heat treatment. These materials have been successfully used as functional fillers to enhance the performance of fluorine–olefin vinyl ether copolymer (FEVE) fluorocarbon coatings. The tribological and electrochemical impedance spectroscopy results indicated that PMTC and TO whiskers can significantly enhance the friction and corrosion resistance of FEVE composite coatings compared with KMTO/FEVE composite coatings. Particularly, the 5 wt. % PMTC/FEVE composite coating displays an enhanced wear resistance (Friction coefficient is 0.632. Wear volume loss is 0.006 mm3) than that of pure FEVE coating. (Fiction coefficient is 0.865 and wear volume loss is 0.177 mm3.) And the |Z|0.01 Hz value of 10 wt.% TO/FEVE composite coating is 109.8 Ω·cm2, which indicates its highly protective nature when compared to that of pure coating (~ 107 Ω·cm2). Besides, the microstructure of cross sections, worn surfaces and wear debris of the composite coatings was analyzed by scanning electron microscopy (SEM), and the related anti-wear and anti-corrosion mechanisms were revealed. The present process and design can be extended to the synthesis and modification of a variety of other layered materials including titanates, tantalates, chalcopyrites, etc.
... Main sensing mechanism is based on the Grouthuus chain reaction [17]. At the same time, barium titanate was also proven to be very good material for humidity sensing [18,19]. Generally, when relative humidity (RH) is low, water molecules chemisorb on the grain surfaces due to the formation of chemical bond between active metal oxide surface and oxygen of the first water layer. ...
... In the composite ceramics with higher amount of magnetic phase a distortion in the crystal lattice obviously occurred and can be correlated with magnetoelectric coupling in the composite. On the other hand, it is proven by previous research [7,18] that by slight doping of barium titanate, lattice can be deformed and tetragonal structure can change into the pseudo-cubic. The possible explanation can be also interpreted by the fact that doping with very low amount of Fe during the sintering process (that cannot be noticed from the XRD) can also affect change of BT crystal lattice and can lead toward the pseudo-cubic type of crystal symmetry. ...
Composites based on barium titanate and nickel zinc ferrite doped with cooper and samarium were prepared by a mixing method. The formation of barium titanate tetragonal crystal structure and nickel zinc ferrite cubic spinel structure was identified. Polygonal grains were formed in all three types of ceramics. Due to the very high conductivity of ferrite phase in the materials the ferroelectric hysteresis loops were roundish and not typical for classical ferroelectric material. The break down field was found to be similar for all compositions. Leakage current measurements have shown the existence of different types of conductivity mechanisms in each material. The impedance analysis suggested a bit stronger impact of grain boundaries on total conductivity of the composites and the mechanism of polaronic conduction of two types. The magnetization of the composites is lower than for the pure ferrite phase and corresponds to the weight fraction of the ferrite phase. The soft magnetic nature of these composites might be very useful for development of multifunctional devices which will be able to switch the magnetization with small external magnetic field. Humidity sensing properties of the prepared ceramics were also investigated.
