Structural, dielectric and electrocaloric properties of (Ba0.85Ca0.15)(Ti0.9Zr0.1−xSnx)O3 ceramics elaborated by sol–gel method (original) (raw)
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Solid State Communications, 2016
Ferroelectric ceramics (Ba 0.85 Ca 0.15)(Ti 0.9 Zr 0.1−x Sn x)O 3 (x = 0.00, 0.02, 0.04, 0.06) were elaborated by sol-gel method. Structural investigation revealed coexistence of tetragonal (P4mm) and orthorhombic (Pmm2) symmetries at room temperature for the undoped ceramic, while only a tetragonal structure (P4mm) was observed for the doped ceramics. Dielectric measurements indicate a dielectric relaxation process at high temperatures which is essentially related to the hopping of oxygen vacancies VÖ. Furthermore, a down shifting of the Curie temperature (T C) with increasing Sn 4+ doping rate has been revealed. The temperature profiles of the Raman spectra unveiled the existence of polar nanoregions above the Curie temperature in all ceramics. The ferroelectric properties were found to be related to the microstructure. Electrocaloric effect was investigated in this system that revealed an electrocaloric responsivity of 0.225 × 10 −6 K m/V for the composition with x = 0.04 Sn doping, where other remarkable physical properties were also observed.
Journal of Alloys and Compounds, 2017
Ba 0,95 Sr 0,05 (Ti 0,95 Zr 0,05) 1-x Sn x O 3 (x ¼ 0 and x ¼ 0.025) ceramics were prepared by solid state method. We have systematically studied the effects of a low quantity of Sn substitution on the crystal structure, dielectric and electrocaloric properties. X-ray diffraction shows that the symmetry of the two compositions x ¼ 0 (BSTZ) and x ¼ 0.025 (BSTZS) is both tetragonal with a space group P4mm and orthorhombic with Pmmm space group. Dielectric measurements show that Sn doping significantly reduces the Curie temperature from 392 K for BSTZ to 364 K for BSTZS. A typical hysteresis loops were observed for the investigated compositions and they were confirmed the ferroelectric-to-paraelectric transition phase. Finally electrocaloric effect in lead-free BSTZ and BSTZS ceramics is studied using an indirect method from the thermal variation of P-E hysteresis loops using the Maxwell relation. In the composition x ¼ 0, the electrocaloric temperature DT was about 0.048 K. The addition of a low quantity of tin (Sn) ions in the matrix of Ba 0,95 Sr 0,05 (Ti 0,95 Zr 0,05) has been able to increase the electrocaloric temperature until DT reached 0.095 K to a field E ¼ 1 kV/mm.
2021
We have studied the effects of Zn and Nb substitutions on dielectric, ferroelectric, and piezoelectric properties of Ba0.87Ca0.13(Ti0.9Zr0.1)(1−x)(Zn1/3Nb2/3)xO3 ceramics. X-ray diffraction (XRD) results display that morphotropic boundary occurs from tetragonal to orthorhombic region for x = 0; 0.005; 0.01 and polymorphic phase transitions from tetragonal to orthorhombic and rhombohedral regions for x = 0.02. The evolution of the Raman spectra demonstrates the introduction of a disorder in this composition, which promotes ferroelectric relaxor behaviors. Ferroelectricity is confirmed by hysteresis investigation. A piezoelectric coefficient of d33 = 205 pC N−1 and a high planar electromechanical coupling factor of kp = 47% are reported for x = 0.1. The ceramics for x = 0.01 also depicts uniform microstructure that contributes to the important electrical properties. These results indicate that this Ba0.87Ca0.13(Ti0.9Zr0.1)(1−x)(Zn1/3Nb2/3)xO3 system with optimal composition is a promi...
X-ray diffraction, dielectric and Raman spectroscopy studies of Ba1−xNd2x/3(Ti0.9Zr0.1)O3 ceramics
Ceramics International, 2014
Polycrystalline samples of Ba 1 À x Nd 2x/3 (Ti 0.9 Zr 0.1)O 3 (0 rx r 0.125) have been synthesized by high-temperature solid-state reaction technique. These ceramics were characterized by X-ray diffraction as well as dielectric permittivity measurements and Raman spectroscopy. The ceramic samples crystallize in the tetragonal perovskite structure for x ¼0 and in cubic for 0.025r x r 0.125. Dielectric measurements showed that prepared compositions exhibit an evolution from a classical ferroelectric to a relaxor ferroelectric with rising substitution rate x. T C or T m decreases when neodymium (Nd) is introduced in the lattice of Ba(Ti 0.9 Zr 0.1)O 3. A relaxor character with ΔT m ¼12 K and ε 0 r about 11.650 at 1 kHz with T m ¼ 212 K was found for Ba 0.9 Nd 0.06 (Ti 0.9 Zr 0.1)O 3 composition. The evolution of the Raman spectra was studied as a function of compositions and temperatures. The results of the Raman spectroscopy studies confirm our dielectric measurements.
Influence of Ca substitution on microstructure and electrical properties of Ba(Zr,Ti)O3 ceramics
Ceramics International, 2013
In the present work, lead-free (Ba 1 À x Ca x)(Zr 0.04 Ti 0.96)O 3 (x¼ 0.00-0.09) ceramics were fabricated via a solid-state reaction method. The microstructure and electrical properties of the ceramics were investigated. The microstructure of the BCZT ceramics showed a core shell structure at compositions of x¼ 0.03 and 0.06. The substitution of small amount of Ba 2 þ by Ca 2 þ resulted in an improvement of the piezoelectric, dielectric and ferroelectric properties of the ceramics. The orthorhombic-tetragonal phase transition was found in the composition of xr 0.03. Piezoelectric coefficient of d 33 $ 392 pC/N and lowest E c $ 3.3 kV/cm with highest P r $ 14.1 mC/cm 2 were obtained for the composition of x¼ 0.03 while its Curie temperature (T C) was as high as 125 1C. However, the ferroelectric to paraelectric transition temperature had slightly shifted towards room temperature with increasing Ca 2 þ concentration.
Materials Science and Engineering: B, 2010
Lead-free Ba 0.7 Ca 0.3 Ti 1-x Sn x O 3 (x = 0.00, 0.025, 0.050, 0.075, and 0.1, abbreviated as BCST) electroceramic system was prepared by solid state reaction method and investigated its ferroelectric, piezoelectric and electrostrictive properties. X-ray diffraction shows that the compositions with x ≤ 0.05 exhibit a tetragonal crystal structure having P4mm symmetry; while the compositions x = 0.075 and 0.1 exhibit a mixed P4mm + Amm2 phase coexistence of tetragonal and orthorhombic and P4mm + Pm m pseudo-cubic lattice symmetries, respectively at room temperature. The dense microstructure having relative density ~90-92% and average grain size in the range ~2.36 µm to 8.56 µm was observed for BCST ceramics. Temperature dependent dielectric measurements support the presence of phase coexistence Accepted Article This article is protected by copyright. All rights reserved. and show the decrease in Curie temperature (T C) with Sn 4+ substitution. The dielectric loss (tan δ) values in the temperature range (-100 ᵒC to 150 ᵒC) was observed to be less than 4%, for all BCST ceramics. The BCST compositions exhibit typical polarization-electric field (P-E) hysteresis and electric field induced strain (S-E) butterfly loop, which confirms the ferroelectric and piezoelectric character. The compositions x = 0.025, 0.05 and 0.075 show the peaking behavior of displacement current density () to an applied electric field () (J-E) which implies the saturation state of polarization. The maximum electrostrictive coefficient (Q 33) value of 0.0667 m 4 /C 2 was observed for x = 0.075 and it is higher than some of the significant lead based electrostrictive materials. The compositions x = 0.05 and 0.075 exhibit the notable electrostrictive properties that may be useful for piezoelectric Ac device applications. The observed results are discussed and correlated with the structure-propertycomposition.
Journal of Applied Physics, 2014
Ferroelectric phase transition from orthorhombic-to-tetragonal phase was investigated in (Ba 1Àx Ca x)(Zr 0.05 Ti 0.95)O 3 ceramics [x ¼ 0.05, 0.08, 0.10] by micro-Raman scattering. The room temperature Raman scattering reveals the presence of orthorhombic-tetragonal phase coexistence by emergence of tetragonal phase with increase in calcium content. The temperature dependent Raman spectra also show similar cross-over with hardening of A(TO 2) mode and disappearance of A(LO 1) mode as system moves from orthorhombic-to-tetragonal phase. A thermal hysteresis of $10 K was observed in orthorhombic-to-tetragonal transition. V
Journal of materials chemistry. A, Materials for energy and sustainability, 2018
The attention in piezoelectric devices has been moved in the past decade to lead-free ceramics, especially on (Ba,Ca)(Ti,Zr)O3-based materials, due to growing environmental concerns. Here we report a systematic evaluation of the effect that the electric field application has on the structure, microstructure and electrical properties in Ba0.9Ca0.1Ti0.9Zr0.1O3 (BCTZ) lead-free ceramics. Powders were prepared by Pechini method. Dense ceramic samples were sintered at 1275°C for 5h. As observed by X-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS), the ceramics are single perovskite-type structure phase and they are homogeneous both at global and local scale. Rietveld analysis of the diffraction patterns for the non-poled sample is consistent with a coexistence of ferroelectric tetragonal P4mm and rhombohedral R3m symmetries. It is shown that electric field induces changes in rhombohedral-tetragonal relative content that facilitates polarization process of the system. Ceramics exhibit a significant high piezoelectric response with a d 33 value as high as ~390pC/N, which is comparable to soft Pb(Zr1-xTix)O3 (PZTs). Scanning Electron Microscopy (SEM) analysis showed an average grain size of 20 μm and complex ferroelectric domains. A confocal Raman spectroscopy and imaging study carried out on both types of samples reveals that, upon application of an electric field, the E(LO 3) +A 1 (LO 2) +E(TO 4) mode of the Raman spectra shifts to lower frequencies, indicating a reduction of the bonding force between the ions at the B-site of the perovskite (Ti 4+ , Zr 4+) and the oxygen ions of the octahedron for the poled samples. Besides, the spatially resolved mentioned mode of the Raman spectra shows a narrower distribution in the poled sample, monitoring the polarization alignment effect in the direction of the field. These characteristics are related with the complex ferroelectric domain distribution. The polar structure changes after the application of the electric field is revealed, as well by the changes on the dielectric permittivity curves as a function of the temperature. Ceramics also displays a high ferroelectric remnant polarization (Pr=15.3 μC/cm 2) and low coercive field (EC=1.5 kV/cm) at room temperature.
Scripta Materialia, 2018
The lead-free 0.5(Ba 0.7 Ca 0.3)TiO 3 −0.5Ba(Ti 0.8 Zr 0.2)O 3 (BCTZ) ceramics with Er doping have shown good upconversion photoluminescence (PL) and desirable optical temperature sensing properties. To bridge a relationship between the structure/intrinsic defects and properties of rare-earth-doped ferroelectrics, we designed and fabricated a series of BCTZ ceramics doped with 1 mol % Er 3+ by combining the firstprinciples calculations and experimental measurements. Theoretically, we discovered that Er can occupy both A sites (i.e., replacing Ba or Ca) and B sites (i.e., replacing Ti or Zr) in the BCTZ lattice and highlighted that the Erdoping-induced vacancy concentration decreases for both the oxygen vacancies (V o) and cation vacancies (V c). Experimentally, the enhanced PL performance and the dielectric, ferroelectric, and piezoelectric properties of the Er-doped BCTZ ceramics have been observed. Finally, the physical origin of Er-induced property enhancement in BCTZ has been elaborated according to the charge density and chemical bonding analysis. These results open up a path to investigate the effects of site substitution and vacancies on optoelectronic properties of multifunctional rare-earthdoped ferroelectrics.