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The influence of temperature on mode coupling effect in piezoelectric vibrators remains unclear. In this work, we discuss the influence of temperature on two-dimensional (2D) mode coupling effect and electromechanical coupling coefficient of cylindrical [001]c-poled Mn-doped 0.24PIN–0.46PMN–0.30PT piezoelectric single-crystal vibrator with an arbitrary configuration ratio. The electromechanical coupling coefficient kt decreases with temperature increasing, whereas k33 is largely invariant in a temperature range of 25 °C–55 °C. With the increase of temperature, the shift in the 'mode dividing point' increases the scale of the poling direction of the piezoelectric vibrator. The temperature has little effect on coupling constant Γ. At a given temperature, the coupling constant Γ of the cylindrical vibrator is slightly greater than that of the rectangular vibrator. When the temperature changes, the applicability index (M) values of the two piezoelectric vibrators are close to 1, indicating that the coupling theory can be applied to piezoelectric vibrators made of late-model piezoelectric single crystals. [ABSTRACT FROM AUTHOR]

Lead-free (1-x)Bi0.5Na0.5TiO3-xBiCoO3 (x = 0, 0.015, 0.025, 0.03, 0.035, 0.04, and 0.06) piezoelectric ceramics have been synthesized and their structure and electric properties have been investigated systemically. The rhombohedral-tetragonal morphotropic phase boundary (MPB) locates near x = 0.025-0.035. For the ceramics with x = 0.025, the saturated polarization (Ps), remnant polarization (Pr), coercive field (Ec), strain(S), piezoelectric constant (d33), and thickness electromechanical coupling factor (kt) are 40.6 μC/cm2, 35.4 μC/cm2, 5.25 kV/mm, 0.11%, 107pC/N, and 0.45, respectively. The low temperature humps of relative dielectric constant, which is indicative of TR-T, are becoming inconspicuous gradually with the increasing x and almost disappear at x = 0.04. The depolarization temperature Td decreases first and then increases with the increasing x. Our results may be helpful for further work on Bi0.5Na0.5TiO3-based lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Here we report the 0.94(BiNa)TiO-0.06Ba(ZrTi)O (0.94BNT-0.06BZT) lead-free ceramics was synthesized by two-step solid state reaction route. The structural, dielectric, ferroelectric, piezoelectric and electromechanical properties of the ceramics were studied, and showed excellent electric properties ( P = 39.9 μC/cm, P = 33.7 μC/cm, E = 2.79 kV/mm, S = 0.20%, d = 174 pC/N, k = 0.33). The depolarization temperature ( T ) of the ceramics is about 65 °C, which is determined from the first hump of relative dielectric constant. The electromechanical factor k disappears at 65 °C, is consistent with the depolarization temperature ( T ) and the ferroelectric-antiferroelectric phase transition temperature ( T ) determined from the temperature-dependent P- E and bipolar S- E curves. These results indicate the 0.94BNT-0.06BZT ceramics has a good thermal stability in range of − 60-60 °C, and meets the actual demand. [ABSTRACT FROM AUTHOR]

The structures, Curie temperature, dielectric relaxor behaviors, ferroelectricity, ferromagnetism, and magnetocapacitance of the (1− x) Ba0.70 Ca0.30 TiO3- x BiFeO3 [(1− x) BCT- x BF, x = 0-0.90] solid solutions have been systematically investigated. The ceramics have coexisted tetragonal (T) and orthorhombic (O) phases when x ≤ 0.06, coexisted pseudocubic (PC) and O phases when x = 0.065, coexisted cubic and O phases when 0.07 ≤ x ≤ 0.12, PC phase when 0.21 ≤ x ≤ 0.42, coexisted T and rhombohedral (R) phases when 0.52 ≤ x ≤ 0.70, and R phase when x ≥ 0.75. Significantly, composition-dependent microstructures and Curie temperature are observed, the average grain size increases from 1.9 μm for x = 0, reaches 12.0 μm for x = 0.67, and then decreases to 1.3 μm for x = 0.90. At room temperature, the ceramics with x = 0.42-0.70 show piezoelectric properties and multiferroic behaviors, characterized by the polarization-electric field, polarization current intensity-electric field, and magnetization-magnetic field curves, the composition with x = 0.67 has maximum polarization, remnant polarization, maximum magnetization, and remnant magnetization of 15.0 μC/cm2, 9.1 μC/cm2, 0.33 emu/g, and 0.14 emu/g, respectively. In addition, the magnetocapacitance is evidenced by the increased relative dielectric constant with increasing the applied magnetic field ( H). With Δ H = 8 kOe, the composition with x = 0.67 shows the largest values of (εr( H) − εr(0))/εr(0) = 2.96% at room temperature. The structure-property relationship is discussed intensively. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics of (1 − x) Ba0.70 Ca0.30 TiO3- x BiFeO3 [(1 − x) BCT- x BF, x = 0-0.065] have been prepared and investigated. The ceramics with x ≤ 0.06 have diphasic tetragonal and orthorhombic crystal structures, whereas tetragonal phase is suppressed by the introduction of BF. As a result, the composition with x = 0.065 is found to have diphasic pseudocubic and orthorhombic phases. Significantly composition-dependent grain size is observed. With increasing x from 0 to 0.065, the ferroelectric-paraelectric phase transition temperature decreases monotonically from 128°C to 50°C, accompanied by enhanced ferroelectric relaxor behavior, as indicated by the widened diffused phase transition temperature. The room temperature polarization-electric field ( P-E) hysteresis loops and strain-electric field ( S-E) curves indicate that the ferroelectricity enhances slightly and reaches the maximum near x = 0.05, and then weakens with increasing x. On the other hand, the piezoelectric coefficient ( d 33) and electromechanical coupling coefficient ( kp) decrease simultaneously with increasing x, whereas the mechanical quality factor ( Qm) reaches the maximum near x = 0.05. The structure-property relationship is discussed intensively. Our results may be helpful for further understanding and designing BaTiO3-related lead-free ferroelectric/piezoelectric materials. [ABSTRACT FROM AUTHOR]

Pyroelectric measurements are conducted during zero-field heating in [001], [110] and [111] poled 0.69Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 single crystals. Compared to the room-temperature-poled samples, the crystals poled by using the field cooling method show broad but well recognizable pyroelectric current peaks near 190&degree;C, which is much higher than the Curie point (126&degree;C) of the crystal. We propose that this peak of the crystals poled by field-cooling above the Curie point is ascribed to the order-disorder transition of the dipoles in polar nano-regions formed at the Burns temperature. [ABSTRACT FROM AUTHOR]

Surface acoustic wave (SAW) propagation in relaxor-based ferroelectric single crystals 0.93Pb(Zn1/3Nb2/3)03-0.07PbTiÛ3 (PZN-7%PT ) poled along [011]c has been analyzed theoretically The results show that PZN-7%PT single crystals have excellent SAW properties, such as low phase velocities, very high electromechanical coupling coefficients and small power Sow angles. It is also found that the SAW properties strongly depend on the propagation direction and the characteristic curves of SAW phase velocity, and the electromechanical coupling coefficients are symmetric with respect to &thetas; = 90°. Considering all related factors, the X-cut PZN-7%PT single crystal has the best performance. Based on our results, the X-cut PZN-7%PT single crystals poled along [011]c are an excellent candidate for ultra-wide bandwidth low-frequency SAW devices. [ABSTRACT FROM AUTHOR]

We have derived a general formula for sensitivity optimization of gravimetric sensors and have used it to design a high sensitivity gravimetric sensor using unidirectional carbon fiber epoxy composite (CFEC) waveguide layer on (1 − x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-xPT) single crystal substrate with the carbon fibers parallel to the x1 and x2 axes, respectively. The normalized maximum sensitivity (|Smf|λ)max exhibits an increasing tendency with the decrease of (h/λ)opt and the maximum sensitivity (|Smf|λ)max increases with the elastic constant c66E of the piezoelectric substrate material. For the CFEC/[011]c poled PZN-7%PT single crystal sensor configuration, with the carbon fibers parallel to the x1 axis at λ = 24 μm, the maximum sensitivity (|Smf|λ)max can reach as high as 1156 cm2/g, which is about three times that of a traditional SiO2/ST quartz structure gravimetric sensor. The better design selection is to have the carbon fibers parallel to the direction of propagation of Love wave in order to obtain the best sensitivity. [ABSTRACT FROM AUTHOR]

Dispersion relations of Love mode acoustic guided waves propagation in Pb(Mg1/3Nb2/3)O3−33%PbTiO3 (PMN-0.33 PT) single crystal with a gold electrode film are calculated. There is no cross coupling among Love wave modes, which is conducive to eliminating the cross interference between modes. The general formula is derived to precisely measure the thickness of the electrode. More acoustic energy would be concentrated inside the electrode with the increase of film thickness for a given frequency. Compared with the PZT-5 ceramic, [001]c poled PMN-33%PT single crystal has a slower attenuation of the amplitude of the acoustic guided wave. Therefore, single crystal is extremely suitable for making low loss acoustic wave devices with a high operating frequency. [ABSTRACT FROM AUTHOR]

Highlights: [•] The effects of Mn doping on structures, electric, magnetic, and magnetocapacitive properties of the 0.33Ba0.70Ca0.30TiO3–0.67BiFeO3 + x wt%MnO2 (BCT-67BF:Mn100x, x =0–0.6) ceramics have been intensively investigated. [•] The BCT-67BF:Mn100x ceramics with x =0–0.6 have diphasic tetragonal–rhombohedral phases. Mn doping improves the densification and significantly decreases the grain size. [•] As x increases, the relaxor degree increases, the ferroelectricity and piezoelectricity weaken monotonically, while the magnetism enhances firstly, reaching the maximum near x =0.5, and then decreases. [•] The room temperature relative dielectric constant shows an obvious increase with increasing applied magnetic fields (H), the magnetocapacitive coefficient (ε r(H)− ε r(0))/ε r(0) decreases with increasing Mn content, from 2.96% for x =0 – 0.86% for x =0.6 . [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics of Ba0.70Ca0.30Ti1−x Fe x O3 (x=0–0.03) have been synthesized by a conventional solid state reaction method. The influence of Fe content on the microstructure, phase transition, dielectric, ferroelectric, and piezoelectric properties is investigated systematically. The ceramics with x≤0.02 are diphasic composites of tetragonal Ba0.80Ca0.20TiO3:Fe and orthorhombic Ba0.07Ca0.93TiO3:Fe solid solutions. The tetragonal phase is gradually suppressed as x increases, the ceramic with x=0.03 is found to have diphasic pseudocubic and orthorhombic phases. And the grain size is dependent on Fe content significantly. Introduction of Fe at B-sites improves the densification and decreases the sintering temperature. As x increases from 0 to 0.03, the room temperature relative dielectric permittivity enhances, dielectric loss decreases, and the Curie temperature decreases monotonically from 128°C to 58°C. However, the ferroelectricity enhances slightly and reaches the maximum near x=0.005, and then weakens with increasing x. On the other hand, the piezoelectric coefficient (d 33) and the electromechanical coupling coefficient (k p ) decrease simultaneously with increasing x, whereas the mechanical quality factor (Q m ) increases significantly. The structure–electrical properties relationship is discussed intensively to give more information on (Ba,Ca)TiO3-based lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Abstract: The effects of sintering temperature and poling conditions on the electrical properties of tetragonal and orthorhombic diphasic Ba0.70Ca0.30TiO3 (BCT) lead-free ceramics have been systematically investigated. On the one hand, with increasing sintering temperature from 1270°C to 1400°C, the bulk density increases monotonically and the Curie temperature keeps almost constant with the value of ∼120°C, whereas the grain size, the maximum relative dielectric constant, room temperature polarization reach the maximum values for samples sintered at 1340°C. On the other hand, it is found that the piezoelectric property depends on poling electric field and poling temperature significantly. An enhanced piezoelectric behavior of d 33=126pC/N, k p =0.29, and Q m =588 is obtained for the BCT ceramics poled at 100°C with 30kV/cm field for 20min. The aging behavior of the piezoelectric property is also investigated. [Copyright &y& Elsevier]

Surface acoustic wave (SAW) propagation in relaxor-based ferroelectric single crystals 0.93Pb(Zn1/3Nb2/3)03-0.07PbTiÛ3 (PZN-7%PT ) poled along [011]c has been analyzed theoretically The results show that PZN-7%PT single crystals have excellent SAW properties, such as low phase velocities, very high electromechanical coupling coefficients and small power Sow angles. It is also found that the SAW properties strongly depend on the propagation direction and the characteristic curves of SAW phase velocity, and the electromechanical coupling coefficients are symmetric with respect to &thetas; = 90°. Considering all related factors, the X-cut PZN-7%PT single crystal has the best performance. Based on our results, the X-cut PZN-7%PT single crystals poled along [011]c are an excellent candidate for ultra-wide bandwidth low-frequency SAW devices. [ABSTRACT FROM AUTHOR]