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Doping of suitable metal ions in ferroelectric oxides modifies the physical properties and can induce additional functionalities. Here, we present a detailed study on the effects of Sm concentration on the structural, dielectric, ferroelectric, and piezoelectric properties of ((K0.5Na0.5)1−3xSmx)NbO3 (KNSN) (0.00 ≤ x ≤ 0.02) ceramics. X‐ray diffraction and Raman spectroscopic analysis indicate that KNSN ceramics exhibit the single‐phase orthorhombic (Amm2) structure for x = 0.00 and the coexistence of orthorhombic and tetragonal (Amm2 + P4mm) structure for the composition range 0.005 ≤ x ≤ 0.02. The tetragonal phase fraction increases with an increase in Sm concentration. We observed dielectric relaxation behavior in KNSN at orthorhombic to tetragonal (TO–T) phase transition temperature, and its origin can be attributed to the structural heterogeneity at the inter‐ferroelectric phase boundary. Increasing Sm concentration leads to the broadening of the ferroelectric phase transition peaks. Further, the structural heterogeneity of the ceramics was seen from the slope of the dielectric constant versus log frequency and central peak behavior of Raman spectra at room temperature (RT). The study reveals that x = 0.005 shows maximum dielectric constant (Ɛr = 583), remanent polarization (2Pr = 57.02 μC/cm2), and piezoelectric coefficient (d33 = 94 pC/N) at RT and is associated with increased local structural heterogeneity due to Sm doping. [ABSTRACT FROM AUTHOR]

Ferroelectric materials exhibiting switchable and spontaneous polarization have strong potential to be utilized in various novel electronic devices. Solid solutions of different perovskite structures induce the coexistence of various phases and enhance the physical functionalities around the phase coexistence region. The construction of phase diagrams is important as they describe the material properties, which are linked to the underpinning physics determining the system. Here we present the phase diagram of (K0.5Na0.5NbO3)–(Ba0.5Sr0.5TiO3) (KNN-BST) system as a function of composition and their associated physical properties. Lead-free (1 − x)KNN–xBST (0 ≤ x ≤ 0.3) solid solution ceramics were synthesized by conventional solid-state reaction technique. The X-ray diffraction and Raman spectroscopic studies indicate composition-dependent structural phase transitions from an orthorhombic phase for x = 0 to orthorhombic + tetragonal dual-phase (for 0.025 ≤ x ≤ 0.15), then a tetragonal + cubic dual-phase (x = 0.2) and finally a cubic single phase for x ≥ 0.25 at room temperature (RT). Among these, the orthorhombic + tetragonal dual-phase system shows an enhanced value of the dielectric constant at room temperature. The phase transition temperatures, orthorhombic to tetragonal (TO-T) and tetragonal to cubic (TC), decrease with the increase in BST concentrations. The ferroelectric studies show a decrease of both 2Pr and EC values with a rise in BST concentration and x = 0.025 showed a maximum piezoelectric coefficient. [ABSTRACT FROM AUTHOR]

With increasing industrial acceptance of Na0.5Bi0.5TiO3 (NBT)-based lead-free piezoceramics, there is a need to develop insights into the way different factors influence the microstructural–structural–piezoelectric property correlations. In this work, we have examined the role of structural disorder on the piezoelectric response of the pre-MPB composition x = 0.03 of the well-known solid solution series (1-x)Na0.5Bi0.5TiO3-(x)BaTiO3. Using off-stoichiometry on the A-site as a tuning parameter to vary the structural disorder, which we characterize in terms of the fraction of the "cubiclike phase" or variation in the thermal parameter of the A-site cation, it is shown that the piezo response maximizes for the composition, which retains an optimum degree of disorder after poling. Our study confirms the important role of structural disorder in enhancing piezoelectric response in ferroelectric ceramics. [ABSTRACT FROM AUTHOR]

We have investigated the effect of sintering temperature on the microstructure, crystal structure, dielectric, ferroelectric, and piezoelectric properties of the morphotropic phase boundary (MPB) composition lead-free piezoelectric 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 (NBT-6BT). We have found that the specimen sintered at an optimized temperature (1150 °C) exhibits the maximum piezoelectric response (d33 ~ 198 pC/N). The maximum piezoresponse is associated with the presence of optimized structural disorder amidst long-range ferroelectric order in the poled state of the specimen. The structural disorder in the present case is caused by the propensity for stabilizing in-phase octahedral tilt. [ABSTRACT FROM AUTHOR]

A-site off-stoichiometry has been an efficient method to enhance the electromechanical properties of lead-free Na0.5Bi0.5TiO3(NBT)-based piezoceramics. In this work, we have reported the effect of Na/Bi off-stoichiometry on the microstructural, structural, and electromechanical properties of the tetragonal 0.80Na0.5Bi0.5TiO3–0.20BaTiO3 (NBT–20BT) ceramic. The maximum piezoresponse ~ 115 pC/N is obtained for 4 mol% Na-deficient (20BT–Na46) and 2 mol% Bi-excess (20BT–Bi52) compositions. It is a 25% increment over the piezoresponse of the stoichiometric composition (20BT–Na50 ~ 90 pC/N). The enhancement in piezoresponse has been attributed to an optimized presence of polar-structural heterogeneity/disorder in the poled ceramic matrix and an optimized distortion of the long-range tetragonal ferroelectric phase. It is established that A-site off-stoichiometry is influencing the polar-structural heterogeneity/disorder and tetragonal lattice distortion via the grain size. [ABSTRACT FROM AUTHOR]

Doping of suitable metal ions in ferroelectric oxides modifies the physical properties and can induce additional functionalities. Here, we present a detailed study on the effects of Sm concentration on the structural, dielectric, ferroelectric, and piezoelectric properties of ((K0.5Na0.5)1−3xSmx)NbO3 (KNSN) (0.00 ≤ x ≤ 0.02) ceramics. X‐ray diffraction and Raman spectroscopic analysis indicate that KNSN ceramics exhibit the single‐phase orthorhombic (Amm2) structure for x = 0.00 and the coexistence of orthorhombic and tetragonal (Amm2 + P4mm) structure for the composition range 0.005 ≤ x ≤ 0.02. The tetragonal phase fraction increases with an increase in Sm concentration. We observed dielectric relaxation behavior in KNSN at orthorhombic to tetragonal (TO–T) phase transition temperature, and its origin can be attributed to the structural heterogeneity at the inter‐ferroelectric phase boundary. Increasing Sm concentration leads to the broadening of the ferroelectric phase transition peaks. Further, the structural heterogeneity of the ceramics was seen from the slope of the dielectric constant versus log frequency and central peak behavior of Raman spectra at room temperature (RT). The study reveals that x = 0.005 shows maximum dielectric constant (Ɛr = 583), remanent polarization (2Pr = 57.02 μC/cm2), and piezoelectric coefficient (d33 = 94 pC/N) at RT and is associated with increased local structural heterogeneity due to Sm doping. [ABSTRACT FROM AUTHOR]