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We reported the effect of Erbium (Er with x = 0.005, 0.01, 0.015, 0.02, 0.025 and 0.03)-substituted Ba0.8Ca0.2Ti0.975(Nb0.5Yb0.5)0.025O3 lead-free ceramics. Structural, dielectric, piezoelectric, ferroelectric and photoluminescence properties of all ceramics were systematically explored. At room temperature, X-ray diffraction (XRD) analysis showed that (Ba0.8Ca0.2)1-xEr2x/3 □ x/3Ti0.975(Nb0.5Yb0.5)0.025O3 samples (Abbreviated as BCTYN-xEr) exhibited a pure tetragonal phase for x ≤ 0.025. However, the composition (x = 0.03) showed the formation of an additional phase. The vibrational study was found to correlate strongly with XRD analysis. The dielectric properties were improved in the composition x = 0.01, where the dielectric constant was increased from 5824 for x = 0 up to 6150 for x = 0.01. The composition (x = 0.005) revealed the optimum properties with a d33 piezoelectric coefficient of 88 pC/N, a kp planar electromechanical coupling factor of 16.9% and a Pr remanent polarization of 9.25 μC/cm2. The photoluminescence (PL) results showed, at 525 nm and 550 nm, two strong green bands. As multifunctional materials, BCTYN-xEr samples represent a great potential in the applications of mechanical–electro-optical coupling and integration devices. [ABSTRACT FROM AUTHOR]

The present paper reports the effect of Yttrium substitution on the structural, microstructure, dielectric, ferroelectric, and electrocaloric (EC) properties of the lead-free (Na0.5 Bi0.5)0.94 Ba0.06TiO3 (abbreviated as NBT-6BT) ceramics. For a small quantity of Yttrium (x = 0.01 and 0.05), the X-ray diffraction and Raman spectra exhibit the coexistence of rhombohedral and tetragonal phases at room temperature. However, with x = 0.08 composition, a structural change to pseudo-cubic phase was identified. By adding a small amount of Yttrium, the ferroelectric properties were improved by increasing the remnant polarization from (Pr = 27µC/cm2) for x = 0 up to (Pr = 36µC/cm2) for x = 0.01. This resulted in an improvement of 30% in the estimated ferroelectric parameters as well as an improvement in the piezoelectric properties, as measured by the value of d33 of 130 pC/N. The electrocaloric temperature change (ΔT) is calculated by a direct method using Differential Scanning Calorimetry (DSC) to be at more than 1 K at 5 kV/mm for x = 0.01. Despite the minimal amount employed, our observations lead us to say that the introduction of Yttrium into the NBT-6BT ceramic has directly affected the properties of this material. Nevertheless, with a higher content of Yttrium (x = 0.08), a sudden decrease of both ferroelectric and EC effect was observed. The declined properties at higher contents may originate from the structural change which can influence the polar distribution in the structure. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of Ba 1−x Ca x Ti 0.975 (Nb 0.5 Yb 0.5 ) 0.025 O 3 (where x = 0.15, 0.2 and 0.3, abbreviated as BCTYN) were prepared by the conventional solid state reaction method. The effect of calcium (Ca) substitution in BaTi 0.975 (Nb 0.5 Yb 0.5 ) 0.025 O 3 (abbreviated as BTYN25) on the structural, dielectric, piezoelectric and ferroelectric properties and electro-caloric effects (ECE) was investigated. X-ray diffraction (XRD) results at room temperature showed that the BCTYN samples in the composition x < 0.3 exhibited a pure tetragonal perovskite structure. Dielectric measurements showed a classical ferroelectric behavior for all samples. With the increase of the Ca content, the Curie temperature ( T C ) was still maintained with a small shift towards low temperature. The evolution of the Raman spectra was studied as a function of compositions and temperatures. The Raman bands confirmed the structure and the phase transition of the BCTYN ceramics. By adding Ca, the piezoelectric properties and the remanent polarization ( P r ) are relatively maintained for the compositions x = 0.15 and x = 0.2. A piezoelectric coefficient of d 33 = 130 pC/N and a planar electromechanical coupling factor of k p = 28% were obtained for these compositions. Two different methods were used to calculate the electro-caloric coefficients of the BCTYN ceramics. The incorporation of Ca was found to enhance the electro-caloric strength ( ξ = Δ T /Δ E ) within a broad temperature range with a best value of ξ = 0.2 Kmm / kV for x = 0.2. [ABSTRACT FROM AUTHOR]

In this study, lead-free Ba 0.85 Ca 0.15 Ti 0.95 (Nb 0.5 Yb 0.5) 0.05 O 3 (BC15TYN5) ceramic has been successfully obtained through the conventional solid-state reaction. It has been found the multifunctionality of the BC15TYN5 ceramic. It exhibits ferroelectric properties, with a significant remanent polarization value of about P r = 9.36 μC/cm2, and a recoverable energy storage density value of about W rec = 42.21 mJ/cm3. Additionally, it displays a dielectric permittivity of about ε ′ r = 7230 around T C = 80 °C, and an electro-caloric strength value of about ξ = 0.12 K mm/kV. It's worth noting that these values surpass those typically found in BaTiO 3 ceramics elaborated with similar experimental conditions. Electrical study (impedance, modulus, and conductivity characteristics) is essential for characterizing the BC15TYN5 material, determining its suitability for various technological applications, and optimizing manufacturing processes. The Cole-Cole plots exhibited two relaxations associated with the contribution of the grains and grain boundaries. The relaxation times for both grains and grain boundaries showed temperature-dependent variation following Arrhenius relation. The measured AC conductivity was evaluated by applying the Jonsher power law. Based on the thermal evolution of the exponent S , it was confirmed that the conduction mechanism follows the Correlated Barrier Hopping (CBH) model. These properties make BC15TYN5 ceramic suitable for applications such as dielectric capacitors, ferroelectric random-access memories, electrical energy storage units, and electro-caloric refrigeration systems. [ABSTRACT FROM AUTHOR]

Ba 1-y-x Pr 2y/3 ⃞ y/3 (Na 0.5 Bi 0.5) x Ti 0.9 Zr 0.1 O 3 (y = 0.005; x = 0.05, 0.1 and 0.15) (BZT-Pr-xNBT) ceramics were prepared using a solid state reaction method. X-ray diffraction (XRD) analysis at room temperature (RT) showed a tetragonal perovskite structure for all compositions. By adding Na 0.5 Bi 0.5 TiO 3 (NBT) on BZT-Pr ceramic, a core-shell grain structure is developed, responsible for an improved dielectric temperature stability with broadened curves at the lower dielectric peak (T l) and the Curie temperature (T C). The temperature coefficient of capacitance curve of the composition BZT-Pr-0.15NBT satisfied the EIA X7R specification and the T C value is successfully increased. These compositions are of relaxor type at T l , which was found near RT. All Raman bands show a broadening with the increasing of NBT content. The remanent polarization (P r), the coercive field (E C) and the piezoelectric coefficient (d 33) decrease when the NBT content increases. The photoluminescence (PL) results exhibit a strong red emission (at 617 nm and 649 nm) for all ceramics. • Ba 1-y-x Pr 2y/3 q y/3 (Na 0.5 Bi 0.5) x Ti 0.9 Zr 0.1 O 3 (y=0.005; x=0.05, 0.1 and 0.15) ceramics were prepared. • The dielectric temperature stability was improved. • The composition BZT-Pr-0.15NBT satisfied the EIA X7R specification. • All compositions are of relaxor type near RT. [ABSTRACT FROM AUTHOR]

A lead-free BaTi 0.975 (Nb 0.5 Yb 0.5 ) 0.025 O 3 (BTYN25) ceramic sample was prepared using a solid state reaction method. The polymorphic phase transition (PPT) from the orthorhombic to the tetragonal phase (O-T) at room temperature (RT) was identified in this composition. An X-ray diffraction (XRD) study allowed the identification of those two structures at RT. Dielectric measurements made it possible to determine the phase transitions. The Raman study confirmed the structures and the phase transitions. A good piezoelectric coefficient of d 33 = 140 pC/N, a planar electromechanical coupling factor of k p = 29% and a remanent polarization of P r = 10.8 μC/cm 2 were obtained. The electro-caloric effect (ECE) was investigated by using two different methods: an indirect method with hysteresis loops and a direct method with a modified Differential Scanning Calorimeter (DSC). A good electro-caloric strength ( ξ = ΔT / ΔE ) of ξ = 0.17 °C mm/kV near the ferroelectric-paraelectric phase transition temperature was obtained. At RT, a significant electro-caloric strength of ξ= 0.05 °C mm/kV was found due to the coexistence of the two phases: the orthorhombic one and the tetragonal one. A good agreement between the two methods was found. These values are very interesting when compared to those for other materials and show the possibility of using such lead-free ceramics for electro-caloric applications. [ABSTRACT FROM AUTHOR]

The effect of Pr 3+ addition on structural, electrical, and optical properties of Ba 1− x Pr 2 x /3 Ti 0.925 (Yb 0.5 Nb 0.5 ) 0.075 O 3 (0.3% ≤ x ≤ 1%) ceramics was investigated. X-ray studies have allowed the identification of a continuous solid solution with P 4mm-tetragonal symmetry of all prepared samples. Incorporation of Pr 3+ was found to improve ferroelectric and piezoelectric properties with an optimum at the critical concentration of 0.005. Photoluminescence properties revealed that the introduction of Pr 3+ ions gives rise to the green and red photoemissions and permitted to shed more light on the created structural disorder and shallow defects. This effect was confirmed by Raman spectroscopy investigation. The presence of Pr element in such materials may have significant technological promise in novel multifunctional devices. [ABSTRACT FROM AUTHOR]