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Microstructural evolving sequence of relaxor ferroelectric Ba6 Zr2 Nb8 O30 ( BZN) ceramics has been investigated and discussed. Porous BZN, which has an irregular grain network with pores, can be obtained within a narrow sintering window (sintering temperature of ~1250°C and dwelling time of ~5 h in our experiments). X-ray diffraction-based structure refinements determine the atomic positions and confirm that the porous ceramics has tetragonal tungsten bronze structure with P4 bm space group symmetry. It is found that the most porous ceramic has the lowest dielectric constant, highest electric field breakdown strength, and nearly zero macroscopic electric field-induced strain. These features can be related to the porous microstructures by comparing with the denser counterparts and can be well understood by using brick-wall model. Our results may provide useful information for the understanding of microstructure evolving sequence of BZN during sintering and the structural effects on electric properties of ceramics. Our work may also provide a reliable way for developing porous ferroelectric ceramics with special properties. [ABSTRACT FROM AUTHOR]

Ceramic composites of (1‐x)Pb0.99{Nb0.02[(Zr0.57Sn0.43)0.937Ti0.063]0.98}O3 (PNZST)/xZnO were recently reported to exhibit exceptionally high pyroelectric coefficients near human body temperature due to the ferroelectric‐antiferroelectric transition of the matrix grains. In the present work, a comparative study is conducted on two composites of x = 0.1 and 0.4 with in situ heating transmission electron microscopy (TEM). The results verify the presence of strain field in the PNZST grain adjacent to a ZnO particle and the stabilized ferroelectric phase at room temperature in the composite of x = 0.1. During heating, the ferroelectric matrix grain transforms to the antiferroelectric phase, contributing to the pyroelectric effect. In the composite of x = 0.4, high‐angle annular dark‐field imaging combined with energy‐dispersive X‐ray spectroscopy reveal the existence of both ZnO and Zn2SnO4. The formation of Zn2SnO4 indicates that Sn in the PNZST matrix grain is selectively extracted, and decomposition of the perovskite phase has taken place. The decomposition products in the form of fine particles are observed to facilitate the nucleation of the antiferroelectric phase and restrict the motion of the phase boundary during heating. The larger amount of ZnO and Zn2SnO4 and the decomposition of the PNZST perovskite phase are suggested to be responsible for the much lower pyroelectric coefficient in the x = 0.4 composite. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectric 0.94Na0.5Bi0.5TiO3‐0.06BaTiO3‐modified antiferroelectric Pb0.99Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 ceramics, (1−x)PNZST‐x(BNT‐6BT), were prepared to acquire high energy storage and thermal stability properties. X‐ray diffraction and element mapping revealed that a solid solution between PNZST and BNT‐6BT occurs, and Ti cations enter the PNZST lattice, partly extruding Sn cations and leading to the formation of isolated SnO2 particles at the grain boundaries and a 0‐3 type composite structure. Such a composite structure helps to create deviatoric stress in the solid solution component. The BNT‐6BT content significantly influences the energy storage capacity, and the x = 0.2 composition renders optimal performance. The room‐temperature‐recoverable energy density and energy efficiency are 2.23 J/cm3 and 78%, respectively, at 260 kV/cm. Both parameters vary less than 6% within a temperature range of 25°C and 125°C. The improved energy storage and temperature stability indicate that the ceramics can potentially be applied in pulse power capacitors and that this relaxor‐modified antiferroelectric ceramic preparation method is a valuable reference for further optimizing the functional properties. [ABSTRACT FROM AUTHOR]

With growing demand for high‐sensitivity infrared detectors in industrial temperature monitoring and medical systems, high‐performance pyroelectric materials are vitally required. In this work, large pyroelectric performance is achieved in (1 − x)Pb0.99Nb0.02[(Zr0.57Sn0.43)0.937Ti0.063]0.98O3–xBaTiO3 (1 − x)PNZST–xBT ceramics by tuning the ferroelectric (FE)‐relaxor phase boundary near room temperature. The FE‐ and ergodic‐relaxor phase boundaries are engineered by breaking the long‐range antiferroelectric order with the introduction of BaTiO3. It is found that the ceramics with x = 0.15 exhibit a large pyroelectric coefficient of 11.3 × 10–4 C m–2 K–1 and figures of merit of Fi = 20.1 × 10–10 m V–1, Fv = 3.44 × 10–2 m2 C–1, and Fd = 3.87 × 10–5 Pa–1/2 around room temperature due to engineered phase boundary. Our results provide the potential technological application for ultrasensitive infrared detector and scientific insights into pyroelectric ceramic design. [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]

In this study, (1−x)Sr0.75Ba0.25Nb2O6‐x[0.94Bi0.5Na0.5TiO3‐0.06BaTiO3] solid solution ceramics were prepared and investigated. The length‐diameter ratio of pillar‐like grain increased with increase in x, reaching maximum value of 10.5 at average length of 1.36 μm and diameter of 0.13 μm for x = 0.20. The maximum dielectric constant, temperature corresponding to the maximum dielectric constant, and saturated polarization decreased, respectively, from 507, 36°C, and 3.2 μC/cm2 for x = 0 to 365, −61°C, and 2.0 μC/cm2 fort x = 0.10, and then increased to 1167, 43°C, and 5.5 μC/cm2 for x = 0.20. These results indicate the competitive effects of B‐site Ti4+ and A‐site Ba2+ on ferroelectricity. [ABSTRACT FROM AUTHOR]

The doping of ZnO is efficient to improve the piezoelectric property and thermal stability of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) based ceramics. However, the underlying physics, especially the local domain structures of the ZnO modified PMN–PT ceramics, which is strongly associated with the electric properties, is not clear yet. In this paper, we investigated the local domain structures and their evolution as a function of x in PMN–0.32PT:xZnO ceramics. It was found that, the domain evolution is mainly caused by the growth of grain size induced by the sintering aiding effect of ZnO at x < 0.04, and the domain evolution can be attributed to the phase transition induced by the partial replacement of Mg2+ by Zn2+ in the B‐site of PMN–PT lattice at x > 0.06. Furthermore, we also investigated the domain structure evolution as functions of temperature and local external electric field in PMN–0.32PT:0.06ZnO ceramics, which exhibited superior piezoelectric property relative to other compositions. We found that the irregular nanodomains are more stable at high‐temperature range, and the regular non‐180° domains exhibited more complex rotation behavior under local electric field, which probably leads to the thermal stability and piezoelectric property enhancement in the ZnO‐modified PMN–0.32PT ceramics. [ABSTRACT FROM AUTHOR]

Ferro‐/piezoelectric ceramics with high performances are generally found at the morphotropic phase boundary (MPB), where two or more different ferroelectric phases coexist. However, the MPB region is usually very narrow; for example, that of (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3 (PMN‐xPT) locates between x = 0.30−0.34. Herein, we report that ZnO‐modified PMN‐xPT polycrystalline ceramics have dramatically broadened MPB regions from x = 0.28, with rhombohedral and monoclinic coexisting phases, to x = 0.36, with tetragonal and monoclinic coexisting phases, as confirmed by powder X‐ray diffraction and piezoresponse force microcopy measurements. The wide MPB region is attributed to lattice distortion caused by the substitution of Zn for Mg cations. As a result, the ceramics show composition insensitive electrical properties over wide composition ranges; for example, the piezoelectric coefficient (d33) and electromechanical coupling factor (kp) remain at near constant values of 450 pC/N and 0.5, respectively, in the range from x = 0.28−0.34. This work not only provides a robust and feasible method to broaden the MPB region but also offers some novel insights into promoting fundamental research on high‐performance piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

The 0-3 type CaBi4Ti4O15:30 wt%BiFeO3 composite shows much better high-temperature piezoelectric properties than the single-phase CaBi4Ti4O15 or BiFeO3 ceramics. The composite with 0-3 type connectivity exhibits a high density of 7.01 g/cm3, a saturated polarization of 21.5 μC/cm2 and an enhanced piezoelectric d33 of 25 pC/N. After the poled composite was annealed at 600°C, its d33 is 21 pC/N at room temperature. Resistance of the composite decreases slowly from 109 ohm at 20°C to ~105 ohm at 500°C. Furthermore, the poled composite shows strong radial and thickness dielectric resonances at 20°C-500°C. [ABSTRACT FROM AUTHOR]

Pure and 1.0 mol% La2O3, ZnO, and Cr2O3-modified 0.675BiFeO3-0.325BaTiO3 ( BF- BT) multiferroic ceramics were prepared and comparatively investigated. For pure and La-, Zn-, and Cr-modified BF- BT, the average grain size is 415, 325, 580, and 395 nm, and the maximum dielectric constant temperature is 460°C, 430°C, 465°C, and 445°C, respectively. All additives weaken the ferroelectricity slightly. Zn- and Cr-modifications dramatically enhance the room-temperature magnetic properties, whereas La-modification has almost no effect on magnetic property. Especially, the Cr-modified BF- BT ceramics show switchable polarization and magnetization of 4.9 μC/cm2 and 0.27 emu/g at room temperature, the magnetoelectric coupling is confirmed by the magnetization-magnetic field curves measured on ceramics before and after electric poling. The mechanism responsible for the different effects of additive on microstructures and properties are discussed based on additive-induced point defect and second phase as well as diffusion-induced substitution. These results not only provide a promising room-temperature multiferroic material candidate, but also are helpful to design new multiferroic materials with enhanced properties. [ABSTRACT FROM AUTHOR]

Er-doped 0.94 Bi0.5 Na0.5 TiO3-0.06 BaTiO3 ( BNT-6 BT: x Er, x is the molar ratio of Er3+ doping) lead-free piezoceramics with x = 0-0.02 were prepared and their multifunctional properties have been comprehensively investigated. Our results show that Er-doping has significant effects on morphology of grain, photoluminescence, dielectric, and ferroelectric properties of the ceramics. At room temperature, the green (550 nm) and red (670 nm) emissions are enhanced by Er-doping, reaching the strongest emission intensity when x = 0.0075. The complex and composition-dependent effects of electric poling on photoluminescence also have been measured. As for electrical properties, on the one hand, Er-doping tends to flatten the dielectric constant-temperature (εr- T) curves, leading to temperature-insensitive dielectric constant in a wide temperature range (50°C-300°C). On the other hand, Er-doping significantly decreases the ferroelectric-relaxor transition temperature ( TF-R) and depolarization temperature ( Td), with the TF-R decreasing from 76°C to 42°C for x = 0-0.02. As a result, significant composition-dependent electrical features were found in ferroelectric and piezoelectric properties at room temperature. In general, piezoelectric and ferroelectric properties tend to become weaker, as confirmed by the composition-dependent piezoelectric coefficient ( d33), planar coupling factor ( kp), and the shape of polarization-electric field ( P- E), current-electric field ( J-E), bipolar/unipolar strain-electric field ( S-E) curves. Furthermore, to understand the relationship between the TF-R/ Td and the electrical properties, the composition of x = 0.0075 has been intensively studied. Our results indicate that the BNT-6 BT: x Er with appropriate Er-doping may be a promising multifunctional material with integrated photoluminescence and electrical properties for practical applications. [ABSTRACT FROM AUTHOR]

Sr2 FeMoO6 ceramics with different Fe/ Mo antisite defect ( ASD) concentrations and grain-boundary ( GB) properties were prepared. The competitive and combining effects of GB and Fe/ Mo ASD on the transport and magnetoresistance were discussed. The GB properties, that is, intergrain coupling strength, positively related with resistivity value, is extremely sensitive to the total flux of reducing gas, in general, lower total gas flux leads to larger resistivity, thus stronger intergrain coupling strength, and then the contributions of GB effect to low-field magnetoresistance ( LFMR) increase appreciably regardless of the amount of ASD. In detail, when ASD concentration is less than 26%, LFMR is dominantly controlled by the GB effect. However, the suppressed ASD effect on LFMR behavior comes to play when the ASD content is larger than or equal to 26%, where the GB and ASD effects contribute together to the LFMR. [ABSTRACT FROM AUTHOR]