[en] In this work, lead-free 0.945B0.5N0.5TiO3-0.055BaZrO3 (BNT-BZ) ceramics were synthesized by using conventional solid-state reaction method and the effect of different sintering temperatures (1145 − 1200 ◦C) on its structure and electromechanical properties were investigated. XRD patterns revealed single a phase-perovskite structure for all samples sintered at different temperatures. An optimum sintering temperature enhanced densification, promoted grain growth, and improve the dielectric and piezoelectric properties. However, at low (1145 ◦C) and high (1200 ◦C) sintering temperatures, the BNT-BZ ceramics showed inferior electromechanical properties. BNT-BZ ceramics sintered at an optimum temperature (1175 ◦C) showed an enhanced strain (0.39%) response at an applied electric field of 7 kV/mm with a high dynamic piezoelectric coefficient (d∗ 33 = 557 pm/V). These results can be attributed to the high density of the BNT-BZ ceramics sintered at 1175 ◦C.

[en] The influence of SrZrO3 (SZ) addition on the crystal structure, piezoelectric and the dielectric properties of lead-free Bi0.5Na0.5TiO3 (BNT−SZ100x, with x = 0 − 0.10) ceramics was systematically investigated. A significant reduction in the grain size was observed with SZ substitution. The X-ray diffraction analysis of the sintered BNT−SZ ceramics revealed a single perovskite phase with a pseudocubic symmetry; however, electric poling indicated a non-cubic distortion in the poled BNT−SZ ceramics. With increase in the SZ content, the temperature of maximum dielectric constant (Tm) shifted towards lower temperatures, and the curves became more diffuse. Enhanced piezoelectric constant (d33 = 102 pC/N) and polarization response were observed for the BNT−SZ5 ceramics. The results indicated that SZ substitution induced a transition from a ferroelectric to relaxor state with a field-induced strain of 0.24% for BNT−SZ9 corresponding to a normalized strain of 340 pm/V.

[en] In this investigation copper coated carbon nanotubes (CNTs) were prepared to enhance the interfacial bonding between CNTs and aluminum matrix by the molecular-level mixing process. In optimized plating bath of (1:1) by wt. CNT with Cu, thickness of coated CNTs is reduced to 100 nm to promote uniform distribution of Cu nanoparticle on the surface of pretreated CNTs. The mixing of CNTs was accomplished by ultrasonication and ball milling. Scanning electron microscope analysis revealed the homogenous dispersion of Cu-coated CNTs in nanocomposites samples compared to the uncoated CNTs. The samples were pressureless sintered under vacuum. The densification increased with the increase in the CNTs content and is more pronounced in Cu-coated CNT nanocomposites

[en] In this study, a new lead-free ceramic system of (1-x)Bi_0.5Na_0.5TiO₃-0.065BaTiO₃-xSrZrO₃ BNBT-SZ100x (with x = 0-0.10) was prepared by a conventional solid-state reaction method and its structural and electrical properties were studied. XRD analysis revealed the formation of pure perovskite phase for all ceramics. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature (T_m) shifted towards lower temperatures and the curves become more diffuse with increasing amount of SZ addition. The ferroelectric curves indicated a disruption of ferroelectric order upon SZ addition into BNBT ceramics. A maximum value of remnant polarization (30 μC cm^-2), piezoelectric constant (197 pC N^-1) and electromechanical coupling coefficient (29.4%) was observed for SZ1 ceramics. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Lead-free piezoelectric 0.97(Bi0.5Na0.5Ti1−xNbx)O3-0.03BaZrO3 (BNT-BZ3) ceramics (x = 0 ∼ 0.03) were prepared by a conventional solid-state reaction method. X-ray diffraction patterns revealed the formation of single-phase perovskite structure with x ≤ 0.015. The depolarization temperature and the dielectric constant decreased with increasing Nb content. The remanent polarization (Pr) and the piezoelectric constant (d33) increased from 28 μC/cm2 and 98 pC/N for x = 0 to 31 μC/cm2 and 128 pC/N for x = 0.005, respectively. In addition, the electric field induced strain was enhanced with a maximum value Smax = 0.17% with a normalized piezoelectric coefficient of d∗ 33 = 283 pm/V at an applied electric field of 6 kV/mm for x = 0.015.

[en] The effect of BaZrO₃ (BZ) addition on the crystal structure, ferroelectric, and piezoelectric properties of Na_0.5Bi_0.5TiO₃ (NBT) ceramics synthesized by a conventional solid-state reaction method was systemically investigated. The X-ray diffraction profile reveals the formation of single-phase perovskite structure for all BZ modified NBT ceramics in composition range (x = 0-0.08). With the increase in BZ content, the maximum dielectric constant (T_m) and depolarization temperature (T_d) peaks shift towards lower temperatures. At room temperature, the ferroelectric response increase with increase in BZ concentration. A maximum value of remanent polarization (P_r) 30 μC/cm² was obtained at x = 0.04 and, however, with further increase in BZ content polarizations values decrease. The piezoelectric constant (d₃₃) increased from 60 pC/N for pure NBT to 112 pC/N for x = 0.040. Furthermore, a significant enhancement in the normalized strain (d^*₃₃ = S_max/E_max = 500 pm/V) was observed at x = 0.055 which can be attributed to ferroelectric and relaxor ferroelectric phase transformation. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Lead-free piezoelectric (0.96B_0_._5N_0_._5TiO_3)-0.04BaZrO_3 (BNT-BZ4) was synthesized by using a solid-state reaction method. SEM micrograph shows dense microstructure. X-ray diffraction (XRD) indicated the formation of a BNB-BZ4 single phase having pseudocubic symmetry. A maximum value of remnant polarization (30μC/cm"2) and piezoelectric constant (112 pC/N) was observed for BNT-BZ4 ceramic. The temperature dependences of the dielectric properties of BNT-BZ4 were investigated in the temperature range of 25-600°C at various frequencies (0.1 Hz-1 MHz). The maximum dielectric constant value (ε_r) reaches a highest value of 4046 (at 10 kHz). The electrical properties were investigated by using complex impedance spectroscopy and provided better understanding of relaxation process

[en] Lead-free SrZrO_3-modified Bi_0_._5Na_0_._5TiO_3 (BNT-SZ) ceramics were fabricated by a conventional solid state reaction method. X-ray diffraction analysis reveals a pure perovskite phase without any traces of secondary phases. Scanning electron microscopy images depicts dense grain morphology. The temperature dependences of the dielectric behavior was measured in the temperature range of 50-500 °C at 100 kHz. With the increase in SZ content, the dielectric constant (ε_r) constantly decreased and the maximum dielectric constant temperature (T_m) shifted towards lower temperatures. In addition to this, ferroelectric hysteresis loops indicated a disruption of ferroelectric order and increase in the relaxor character of BNT ceramics with increase in SZ concentration. A maximum values of remnant polarization (32 μC/cm"2) and piezoelectric constant (100 pC/N) were observed at SZ5 and SZ4, respectively

[en] Lead-free piezoelectric ceramics (1−x) [(0.97Bi0.5Na0.5TiO3)]-0.03BaZrO3-xLiNbO3 (BNT-BZ3-xLN) with x = (0 − 0.07) were synthesized using the conventional solid-state reaction method, and their crystal structure, microstructure, and dielectric, ferroelectric and piezoelectric properties were investigated as a function of the LN content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNT-BZ ceramics in this study. The results indicate that the LN substitution into BNT-BZ3 induces a transition from a ferroelectric to a diffuse and/or relaxor state accompanying a field-induced strain of 0.20% for x = 0.05 at an applied field of 6 kV/mm. The corresponding dynamic piezoelectric coefficient for this composition was (Smax/Emax = 333 pm/V). A significant reduction of the coercive field (Ec) and enhancement of the piezoelectric constant (d33) from 98 pC/N for x = 0 to 117 pC/N x = 0.01 was observed.

[en] The dielectric and electromechanical properties of LiNbO_3-modified (1–x) [0.91Na_0_._5Bi_0_._5TiO_3–0.09Ba_0_._7_0Ca_0_._3_0TiO_3]–xLiNbO_3 (abbreviated as (BiNa)TiO_3–(BaCa)TiO_3–LN) lead-free piezoceramics were investigated. The electrical properties revealed that the addition of LiNbO_3 (LN) induces a phase transition from a non-ergodic relaxor to an ergodic relaxor in the (BiNa)TiO_3–(BaCa)TiO_3–LN system. A large electrostrain of ∼0.418% with a normalized strain of ∼690 pm V"−"1 at 6 kV mm"−"1 was observed at the coexistence of the non-ergodic relaxor and ergodic relaxor phases for LN 0.020, where a field-assisted reversible phase transition between metastable ferroelectric and stable ergodic relaxor phases occurs. Subsequently, a gradual enhancement in the temperature stability of the dielectric constant was observed. At 3 mol.% LN, a nearly constant temperature and a frequency-invariant permittivity of ε _r ∼ 3300 over a broad temperature range of 147 °C–306 °C was observed along with small losses from room temperature up to 400 °C. (paper)