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Lead-free Ba0.70Ca0.30TiO3 + x mol% MnO2 (abbreviated as BCTMx, x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0 and 1.2) piezoelectric ceramics were synthesized by the solid-state reaction method. The effects of MnO2 additives on the phase transition, microstructure, dielectric, ferroelectric, strain behaviors and piezoelectric properties are investigated. BCTMx ceramics (x = 0–1.2) exhibit diphasic tetragonal and orthorhombic phases. The tetragonal phase is gradually suppressed by increasing x. As x increases from 0 to 1.2, the Curie temperature (TC) decreases monotonically from 128 to 45 °C, while the grain size, dielectric and ferroelectric properties increase and reach the maximum near x = 0.6. On the other hand, the piezoelectric coefficient (d33) and the electromechanical coupling coefficient (kp%) decrease simultaneously, whereas the mechanical quality factor (Qm), bipolar and unipolar strain increase and reach the maximum values of 684, 0.28% and 0.24%, respectively, near x = 0.6. The optimum electrical performance with ε r = 1323, tan δ = 0.08, TC = 66 °C, Pmax = 12.2 μC/cm2, Pr = 6.9 μC/cm2, EC = 13.3 kV/cm, d33 = 116 pC/N, kp% = 0.22%, Qm = 684 and the normalized strain d 33 ∗ = Smax/Emax as high as 480 pm/V were observed for x = 0.6. The high strain and Qm suggested that the MnO2-modified Ba0.70Ca0.30TiO3 ceramics are promising candidate for high power applications. [ABSTRACT FROM AUTHOR]

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]

In comparison with conventional organic dyes, quantum dots (QDs) have unique optical and electronic properties, which provide QDs with a wide scope of prospective application in biology and biomedicine. However, the toxicity of QDs and the fluorescence intensity of labeled bacteria must precede their application in bacterial imaging and tracing in vivo. Here, we show that treatment with CaCl significantly improved bacterial labeling efficiency of CdSe/ZnS QDs with the CdSe core size of ~3.1 nm (relative fluorescence unit (RFU) value and ratio of fluorescent E. coli) with rising CdSe/ZnS QDs concentration in a concentration-dependent manner. At 12.5 nmol/L CdSe/ZnS QDs concentration, labeled Escherichia coli ( E. coli) DH5 α appeared as short rod-shaped and luminescent with normal size, and the survival rate and ultrastructure did not change in comparison to the control. But the ratio of fluorescent bacteria and RFU were very low. However, the survival rate of transformed E. coli was significantly inhibited by high CdSe/ZnS QDs concentrations (≥25 nmol/L). Moreover, internalization of CdSe/ZnS QDs resulted in ultrastructure damage of transformed E. coli in a concentration-dependent manner (≥25 nmol/L). Therefore, CdSe/ZnS QDs may not suitable for tracing of bacteria in vivo. Moreover, our study also revealed that colony-forming capability assay and transmission electron microscopy could be used to comprehensively evaluate the toxicity of QDs on labeled bacteria. Our findings do provide a new direction toward the improvement and modification of QDs for use in imaging and tracing studies in vivo. [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]