Correction: Composition design,electrical properties,and temperature stability in (1 − x)K0.44Na0.56Nb0.96Sb0.04O3-xBi0.45La0.05Na0.5ZrO3 lead-free ceramics

Correction for ‘Composition design, electrical properties, and temperature stability in (1 − x)K_0.44Na_0.56Nb_0.96Sb_0.04O₃-xBi_0.45La_0.05Na_0.5ZrO₃ lead-free ceramics’ by Jian Ma et al., RSC Adv., 2018, 8, 29871–29878.

The authors regret that an incorrect version of Fig. 4 was included in the original article. The correct version of Fig. 4 is presented below.Open in a separate windowFig. 1FE-SEM surface images of (1 − x)K_0.44Na_0.56Nb_0.96Sb_0.04O₃-xBi_0.45La_0.05Na_0.5ZrO₃ ceramics with (a) x = 0, (b) x = 0.020, (c) x = 0.040, (d) x = 0.060.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Structure,dielectric, and piezoelectric properties of K0.5Na0.5NbO3-based lead-free ceramics

Lead-free ceramics based on the (1 − x)K_0.5Na_0.5NbO₃–xBi(Zn_0.5Ti_0.5)O₃ (KNN–BZT) system obtained via the conventional solid-state processing technique were characterized for their crystal structure, microstructure, and electrical properties. Rietveld analysis of X-ray diffraction data confirmed the formation of a stable perovskite phase for Bi(Zn_0.5Ti_0.5)O₃ substitutions up to 30 mol%. The crystal structure was found to transform from orthorhombic Amm2 to cubic Pm$\bar{3}$m through mixed rhombohedral and tetragonal phases with the increase in Bi(Zn_0.5Ti_0.5)O₃ content. Temperature-dependent dielectric behavior indicated an increase in diffuseness of both orthorhombic to tetragonal and tetragonal to cubic phase transitions as well as a gradual shift towards room temperature. The sample with x ≈ 0.02 exhibited a mixed rhombohedral and orthorhombic phase at room temperature. A high-temperature X-ray diffraction study confirmed the strong temperature dependence of the phase coexistence. The sample with the composition 0.98(K_0.5Na_0.5NbO₃)–0.02(BiZn_0.5Ti_0.5O₃) showed an improved room temperature piezoelectric coefficient d₃₃ = 109 pC/N and a high Curie temperature T_C = 383 °C.

Room temperature powder X-ray diffraction patterns of (1 – x)K_0.5Na_0.5NbO₃–xBi(Zn_0.5Ti_0.5)O₃ system.     

Influence of Al2O3 nanoparticle doping on depolarization temperature,and electrical and energy harvesting properties of lead-free 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 ceramics

In this research article, the effects of Al₂O₃ nanoparticles (0–1.0 mol%) on the phase formation, microstructure, dielectric, ferroelectric, piezoelectric, electric field-induced strain and energy harvesting properties of the 0.94(Bi_0.5Na_0.5)TiO₃–0.06BaTiO₃ (BNT–6BT) ceramic were investigated. All ceramics have been synthesized by a conventional mixed oxide method. The XRD and Raman spectra showed coexisting rhombohedral and tetragonal phases throughout the entire compositional range. An increase of the grain size, T_F–R, T_m, ε_max and δ_A values was noticeable when Al₂O₃ was added. Depolarization temperature (T_d), which was determined by the thermally stimulated depolarization current (TSDC), tended to increase with Al₂O₃ content. The good ferroelectric properties (P_r = 32.64 μC cm⁻², E_c = 30.59 kV cm⁻¹) and large low-field d₃₃ (205 pC N⁻¹) values were observed for the 0.1 mol% Al₂O₃ ceramic. The small Al₂O₃ additive improved the electric field-induced strain (S_max and ). The 1.0 mol% Al₂O₃ ceramic had a large piezoelectric voltage coefficient (g₃₃ = 32.6 × 10⁻³ Vm N⁻¹) and good dielectric properties (ε_r,max = 6542, T_d = 93 °C, T_F–R = 108 °C, T_m = 324 °C and δ_A = 164 K). The highest off-resonance figure of merit (FoM) for energy harvesting of 6.36 pm² N⁻¹ was also observed for the 1.0 mol% Al₂O₃ ceramic, which is suggesting that this ceramic has potential to be one of the promising lead-free piezoelectric candidates for further use in energy harvesting applications.

In this research article, the effects of Al₂O₃ nanoparticles (0–1.0 mol%) on the phase, microstructure, dielectric, ferroelectric, piezoelectric, electric field-induced strain and energy harvesting of the BNT–6BT ceramic were investigated.     

Structural and morphological studies,and temperature/frequency dependence of electrical conductivity of Ba0.97La0.02Ti1−xNb4x/5O3 perovskite ceramics

Conductivity measurements of our polycrystalline perovskite ceramic systems with a composition of Ba_0.97La_0.02Ti_1−xNb_4x/5O₃ (x = 5, 7 and 10, in mol%) were performed, in order to investigate frequency and temperature dependence. Our ferroelectric ceramics were fabricated by the molten-salt method (chemical reaction followed by an evaporation and filtration reaction); X-ray diffraction patterns indicated that a single phase was formed for pure BaLT_1−xNb_4x/5 ceramics. The electrical behavior of the ceramics was studied by impedance spectroscopy in the 500–610 K temperature range. The conductivity was investigated which can be described by the Jonscher law. Both AC and DC electrical conductivities are completely studied as a function of frequency and temperature. The conductivity exhibits a notable increase with increasing Nb-rates. The low-frequency conductivity results from long-range ordering (close to frequency-independent) and the high-frequency conductivity is attributable to the localized orientation hopping process. Impedance analysis was performed revealing conductivity data which fitted the modified power, σ_AC(ω) = Aωⁿ. The frequency dependence of the conductivity plot has been found to obey the universal Jonscher power law. Both AC and DC electrical conductivities are thoroughly studied as a function of frequency as well as temperature. The AC conductivity reveals that correlated barrier hopping (CBH) and non-overlapping small polaron tunneling (NSPT) models are suitable theoretical models to elucidate the conduction mechanisms existing in our compounds. Significantly, by increasing the temperature, the DC conductivity was increased, which verifies the semiconducting nature of the materials.

The frequency- and temperature-dependent conductivity of our polycrystalline perovskite ceramic systems with a composition of Ba_0.97La_0.02Ti_1−xNb_4x/5O₃ (x = 5, 7 and 10, in mol%) was investigated.     

Effect of ZnO on (ferroelectric) fatigue retention and thermal stability of ferroelectric properties in lead free (K0.5Na0.5)(Nb0.7Ta0.3)O3 ceramics

This work investigates and reports the effect of ZnO addition on the ferroelectric properties of (K_0.5Na_0.5)(Nb_0.7Ta_0.3)O₃ (KNNT) ceramics prepared by a solid state reaction method. Though literature is abundant on the study of the effect of ZnO on the sinterability, microstructure and electrical properties of KNN based materials, the effect of ZnO on their ferroelectric properties has seldom been studied in detail, especially in KNNT. In the current study, 2, 4 and 6 wt% of ZnO was added to KNNT ceramics. The XRD results revealed ZnO addition has no effect on the crystal symmetry of KNNT. However, a ZnO secondary phase was found in KNNT ceramics with 4 and 6 wt% ZnO doping. An increase in grain size was observed with increases in the concentration of ZnO, indicating a direct dependence of grain size on the concentration of ZnO in the KNNT matrix. From ferroelectric studies it was observed that a lower electric field was sufficient to get maximum polarization for ZnO doped KNNT samples compared to that of pure KNNT ceramics. A high remnant polarization (P_r = 14.0 μC cm⁻²) and lower coercive field (E_c = 5.6 kV cm⁻¹) was obtained for 2 wt% ZnO doped KNNT. These samples showed the least fatigue (0.8%) after 10⁹ cycles in comparison to pure (5%), 4 wt% ZnO doped (24.9%) and 6 wt% ZnO doped (30%) KNNT ceramics. The diminution in P_s, P_r, and E_c was only 26.0%, 26.2% and 18.5%, respectively, with an increase in measurement temperature, which indicates improved thermal stability in 2 wt% ZnO doped KNNT. From the present study the optimum concentration of ZnO in KNNT is identify to be 2.0 wt% and their improved properties in comparison to the pure KNNT ceramics are discussed in detail.

This work investigates and reports the effect of ZnO addition on the ferroelectric properties of (K_0.5Na_0.5)(Nb_0.7Ta_0.3)O₃ (KNNT) ceramics prepared by a solid state reaction method.     

Studies on structural,dielectric and optical properties of (Ba0.95Ca0.05)1−x(Ti0.8Sn0.2)1−xNaxNbxO3 lead-free ceramics

(Ba_0.95Ca_0.05)_1−x(Ti_0.8Sn_0.2)_1−xNa_xNb_xO₃ (BCNTSNO₃) lead-free ceramics with compositions (x = 0.75, 0.8 and 0.85) were synthesized through the traditional solid-state reaction method. X-ray powder diffraction analysis showed the formation of a single phase compound crystallized in tetragonal space group P4mm. The evolution of Raman spectra displayed a disorder introduced into the structure, which favors a ferroelectric relaxor behavior. The dependence of the dielectric properties on temperature exhibited two composition ranges with different behaviors. Ferroelectric relaxor properties were observed for the compositions x < 0.85 and the classical ferroelectric behavior for x = 0.85. Lead free (Ba_0.95Ca_0.05)_1−x(Ti_0.8Sn_0.2)_1−xNa_xNb_xO₃ ceramics exhibited larger dielectric constants than those of parent crystal NaNbO₃, suggesting that it is a good candidate for lead-free ceramics in several industrial applications. Using UV-Vis spectroscopy, the optical band gap energy of ceramics (Ba_0.95Ca_0.05)_1−x (Ti_0.8Sn_0.2)_1−xNa_xNb_xO₃ is found at 2.89, 2.92, and 3.05 eV for x = 0.75, 0.8 and 0.85, respectively.

(Ba_0.95Ca_0.05)_1−x(Ti_0.8Sn_0.2)_1−xNa_xNb_xO₃ (BCNTSNO₃) lead-free ceramics with compositions (x = 0.75, 0.8 and 0.85) were synthesized through the traditional solid-state reaction method.     

Anomalous behavior above the Curie temperature in (Nd1−xGdx)0.55Sr0.45MnO3 (x = 0, 0.1, 0.3 and 0.5)

Magnetic properties were studied just above the ferromagnetic–paramagnetic (FM–PM) phase transition of (Nd_1−xGd_x)_0.55Sr_0.45MnO₃ with x = 0, 0.1, 0.3 and 0.5. The low-field inverse susceptibility (χ⁻¹) of Nd_0.55Sr_0.45MnO₃ exhibits a Curie–Weiss-PM behavior. For x ≥ 0.1, we observe a deviation in χ⁻¹(T) behavior from the Curie–Weiss law. The anomalous behavior of the χ⁻¹(T) was qualified as Griffiths phase (GP)-like. The study of the evolution of the GP through a susceptibility exponent, the GP temperature and the temperature range of the GP reveals that the origin of the GP is primary due to the accommodated strain. Likewise, the magnetic data reveal distinct features visible only for x = 0.5 at a low magnetic field that can be qualitatively understood as the result of ferromagnetic polarons, entailed by the strong effect of chemical/structural disorder, whose concentration increases upon cooling towards the Curie temperature. We explained the magnetic properties at a high temperature for the heavily Gd-doped sample (x = 0.5) within the phase-separation scenario as an assembly of ferromagnetic nanodomains, antiferromagnetically coupled by correlated Jahn–Teller polarons.

Magnetic properties were studied just above the ferromagnetic–paramagnetic (FM–PM) phase transition of (Nd_1−xGd_x)_0.55Sr_0.45MnO₃ with x = 0, 0.1, 0.3 and 0.5.