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This research explored the influence of Nb5+ doping on the electrical properties and microstructure of [0.852(Bi0.5Na0.5)-0.11(Bi0.5K0.5)-0.038Ba]Ti(1-x)NbxO3 (designated as BNKT-BT). The BNKT-BT samples were fabricated and the XRD results showed that the doping of Nb5+ ions induced a transformation from the coexistence of both rhombohedral and tetragonal phase to a single pseudo cubic phase. Also, the doping of Nb5+ ions caused the temperature of ferroelectric state-ergodic relaxor state transition to decrease below the room temperature (RT). The SEM observations showed that the Nb5+ doping had a minor effect on the grain size of BNKT-BT samples. In addition, the samples achieved a large electrostrain of 0.43% (d*33 = Smax/Emax = 614 pm/V) under 7 kV/mm at RT. Moreover, the aging process employed at 80 °C for two weeks in air could effectively increase the electrostrain from 0.38% to 0.41% under 6 kV/mm (d*33 = 683 pm/V) and reduce the strain hysteresis from 57% to 34%. These results indicated that the B site doping, combined with the aging process, could provide an effective way to enhance the electrostrain performance of lead-free piezoelectric ceramics.

Flash sintering of zinc oxide (ZnO) ceramics can be induced at room temperature (25 °C) by electrical breakdown at high electric field strength. However, a strong discharge may degrade the sample. This study investigated the effects of atmospheric pressure and composition on the onset electric field for the flash sintering of ZnO. The experimental results show that flash sintering of ZnO under a low electric field at room temperature can be achieved by adjusting the atmospheric conditions. Compared with the onset electric field strength under normal atmospheric conditions, the value for flash sintering of ZnO at 20 kPa in a mixture of 20% air +80% argon (Ar) can be reduced by 82% to approximately 700 V/cm. This method also applies to yttrium oxide (Y2O3) for a low electric field in flash sintering at room temperature, and is the first report on flash sintering of Y2O3 at room temperature.

A series of HfO2-modified (Bi0.475Na0.405K0.055Li0.015)0.95Ba0.05Ti(1-x)HfxO3 (x = 0–0.015) lead-free ceramics were prepared. Results of detailed characterizations showed that the addition of HfO2 had little influence on the grain size, and all of the samples showed the pure perovskite structure. As the Hf4+ content increases, the samples changed from the normal ferroelectric phase to the ergodic relaxor state at room temperature, and the ceramics with x = 0.01 showed a high electro-strain of 0.295% at 6 kV/mm. Therefore, this study provides a new insight into of how the HfO2 addition influences the ferroelectric property of the BNT-based ceramics by B-site substitution.

In this study, plate-like Na0.5Bi0.5TiO3 (BNT) templates with perovskite structure were obtained by two-step molten salt synthesis (MSS) method at a low temperature. Firstly, Bi4Ti3O12 precursors were synthesized at 1030 °C in NaCl–KCl molten salt. Secondly, plate-like Na0.5Bi0.5TiO3 particles with perovskite structure were obtained from plate-like layer-structured ferroelectric ceramic of Bi4Ti3O12 by topochemical microcrystal conversion method. Result showed that excessive Na2CO3 was beneficial to facilitate the low temperature synthesis. In the case of an excess of 30 mol% Na2CO3, plate-like BNT particles could be obtained by synthesis at temperatures ranging from 760 °C to 800 °C, which indicated a flexible processing route. Also, it has been observed that plate-like BNT particles show a high aspect ratio with 1 μm in thickness and 10–20 μm in length. These Na0.5Bi0.5TiO3 plate-like particles can be good candidates for the preparation of lead-free BNT-based piezoelectric ceramics with oriented grain microstructure.

The required onset flash sintering temperature of a ZnO ceramic was decreased to as low as room temperature under an applied Alternating Current (AC) field of 3530 V/cm, and the ZnO ceramic achieved 99% of its theoretical density in 40 s without sintering aids. Due to electrical breakdown, flash sintering occurred once the AC field increased to 5 kV even with no increase in sample temperature and conductivity. Electrical breakdown happened at both edges of the sample, a phenomenon observed in thermal infrared images and confirmed by the simulation results. Electrical breakdown can be very useful in flash sintering even at room temperature.

We examined the flash sintering behavior of zinc oxide nanopowder at an onset furnace temperature as low as 50 °C without sintering aids under an AC electric field up to 2800 V/cm. As the electric field applied in the specimens increased and the flash sintering occurred in air, the onset furnace temperature decreased from 190 to 126 °C, while with the thermal insulation method, the onset furnace temperature decreased to 50 °C. The surface temperature of the specimens was observed with a thermal infrared camera, and the peak temperature was 1404 °C. A high density >92% was achieved with thermal insulation flash sintering and an electric field of 2800 V/cm.

The sintering additive 0.4ZnO-0.6B2O3 (abbreviated as ZnB) was proposed to improve the sintering behavior of (K,Na)NbO3 ceramics. The influence of ZnB on the microstructure and electrical properties of (K,Na)NbO3 ceramics was carefully investigated in detail. Results demonstrated that during the sintering process a liquid phase can form at a relative low temperature, which could favor and accelerate the densification of (K,Na)NbO3 ceramics. Moreover, it was found that (K,Na)NbO3 ceramics with 1.2 wt% ZnB exhibited excellent properties with the piezoelectric constant of d33 = 134 pC/N and planar electromechanical coupling coefficient of kp = 40%. Moreover, the field induced strain of 0.135@5 kV/mm was also achieved with this composition. Meanwhile, the mechanism for this enhancement of property was discussed.

The ions doping engineering has already been proved to be an effective approach of adjusting the intrinsic properties of perovskite structured materials and even realizing some new functionality. The polymorphic phase transition effect was put forward to elucidate the enhanced ferroelectric and piezoelectric properties in (K,Na)NbO3-based materials. In current research, Li-Ta modified (K,Na)NbO3 lying in composition region of the coexistence structure was selected as target materials, and Ce2O3 was chose as dopant in order to reveal the effect of ion doping on the target materials. Owing to the sensitive energy state in the coexistence phase structure, an obvious phase evolution from orthorhombic to tetragonal would be brought about by the doping of Ce2O3. When the doping amount was 0.5% mol, the enhanced ferroelectric property (the remnant polarization of Pr = 21.8 μC/cm2), piezoelectric property (the piezoelectric coefficient of d33 = 272 pC/N) and field-induced property (0.13@4 kV/mm) could be achieved.

The (Ba0.94Ca0.06)(Ti0.9Sn0.1)O3 (BCTS) ceramics with pure perovskite structure were prepared by conventional solid-state reaction route with the addition of 0–0.8 mol% MnO2. The crystal structure, microstructure, and electric properties were investigated systematically. X-ray diffraction patterns showed that the addition of MnO2 changed the ratio of the coexistence of orthorhombic and tetragonal phases, which had apparent influences on the piezoelectric properties of ceramics. When the addition amount is 0.2 mol%, the average grain size increases from ~41.88–52.24 µm, and, however, the average grain size decreases with further addition > 0.2 mol%. A good combination of properties and performance could be achieved with the addition of 0.4 mol% MnO2. The mechanical quality factor Qm, dielectric loss tanδ, piezoelectric constant d33, and planar electromechanical coefficient kp measured are 216, 0.011, 578 pC/N, and 0.39, respectively. Therefore, results of this study suggest that the BCTS-Mn ceramics synthesized could exhibit a great potential for piezoelectric component applications.

Water can trigger flash sintering of ZnO powder pellets at room temperature to achieve ~ 98% of the theoretical density in 30 s without any external furnace heating. The specimen conductivity can be increased by > 10,000 times via absorbing water vapor to enable the room-temperature flash. The initial electric field must be higher than a critical threshold to lead to densification, suggesting bifurcation in kinetic pathways. This new cost and energy saving water-assisted flash sintering (WAFS) technology can potentially be applied to consolidate other ceramic materials.

Two-step flash sintering (TSFS) was proposed as a new ceramic fabrication method to achieve fast densification with suppressed grain growth. Using ZnO as an examplar, ~ 96.5% of theoretical density was achieved using TSFS with a grain size of ~ 370 nm, representing a > 3 times reduction of the grain size in comparison with conventional (one-step) flash sintering. Moreover, TSFS achieved this result in a few minutes, > 200 times faster than that needed for conventional two-step sintering to obtain comparable results, thereby representing an opportunity for significant energy and cost savings.

Lead-free (K 0.49 Na 0.51 )(Nb 1−x Sb x )O 3 piezoelectric ceramics were prepared via the conventional sintering method and the effect of the substitution of Nb with Sb on the phase structure, microstructure and electrical properties of the prepared (K 0.49 Na 0.51 )(Nb 1−x Sb x )O 3 ceramics was systematically investigated. The prepared ceramics exhibited a single-phase perovskite structure which changed from a standard orthorhombic structure to a pseudocubic structure as x was increased from 0 to 0.1. X-ray diffraction patterns and Raman spectra obtained for the prepared ceramics clearly revealed that the degree of structural symmetry increased with x . Substituting an appropriate amount of Sb 5+ for Nb 5+ was found to improve the microstructure and thereby enhance the piezoelectric/ferroelectric properties. Further increasing the Sb content resulted in a decrease of the average grain size and a deterioration of the performance. The peak values of the piezoelectric constant d 33 (182 pC/N) and the electromechanical coupling coefficient k p (41%) were obtained for the ceramic with x =0.06.

Reactive template grain growth method was applied to prepare grain oriented 0.94(Na0.52K0.48)NbO3–0.06LiNbO3 ceramics using plate-like NaNbO3 particles as template. A two-step sintering procedure was put forward to obtain textured ceramics with electromechanical coupling factor kp = 64%, piezoelectric constant d33 = 220 pC/N, and in practical application the value of available d33∗ (converse piezoelectric constant) is about 516 pm/V, which are much higher than these of random form with same composition. Based on the analysis for the behavior of piezoelectricity against the measuring frequency and the intensity of external field, a possible mechanism considering the interaction between defect dipoles induced by the doping of Cu2+ and spontaneous polarization dipoles was proposed to elucidate the field-induced giant strain in textured ceramics. This study does not only provide an insight to the origin and coupling effect of two kinds of dipole but also renders a general approach of defect engineering to take advantage of point defect in ceramics realizing certain function enhancement.

The influence of sintering temperature and poling processing on the room temperature phase structure and piezoelectric properties of Li0.058(Na0.51K0.49)0.942NbO3 ceramics were systematically investigated. An approach was proposed to roughly determine the ratio of tetragonal and orthorhombic phase in the as-sintered samples. The result of temperature dependence of the dielectric constant proves this method feasible. The best piezoelectric properties of d33 = 255 pC/N was obtained in specimens sintered at 1040 °C. The dense microstructure and high percentage of 90° domains reorientation during poling processing could explain the best performance of samples for 1040 °C. The loose microstructure and low density for the samples of 980 and 1080 °C are responsible for the worse piezoelectric properties comparing with that of sample for 1040 °C. Meanwhile, the segregation also plays an important role in the deteriorate properties for the sample sintered at 1080 °C.

Li0.05(Na0.51K0.49)0.95(Nb0.95Ta0.05)O3 (abbreviated as KNNLT) with addition of La2O3, CeO2, respectively, were prepared by a conventional ceramic fabrication technique. X-ray diffraction pattern shows that the coexistence of orthorhombic and tetragonal phase structure for KNNLT was not changed by adding La2O3 or CeO2. SEM observation indicates that these two kind dopants have a remarkable effect on the microstructure of KNNLT ceramics. The To–t (temperature for the orthorhombic to tetragonal phase) was shifted toward lower temperature by the addition of rare earth oxide and typical relaxor ferroelectric is demonstrated especially for KNNLT with high content of La2O3. An addition of 0.5% CeO2 could strengthen the piezoelectric and dielectric constant of KNNLT ceramics to some extent. KNNLT ceramics with 0.5% CeO2 obtain optimum electrical properties: d33=272 pC/N, kp=45%, er=784 and tan δ=1.4%.

Cerium dioxide (CeO2)/yttria-stabilized zirconia (YSZ) has long been proven to be an effective buffer layer architecture for high-temperature superconducting coated conductors. In this study, CeO2 films were deposited on YSZ (001) single crystal substrates via reactive unbalanced magnetron sputtering with varying substrate temperature, sputtering pressure, radio frequency sputtering power, and film thickness. High-quality texture was achieved even at ambient temperature, and deposition parameters were optimized to achieve the best degree of in-plane alignment with (111) ϕ scan full width at half maximum around 1.3°. Atomic force microscopy was utilized to investigate film surface morphology and roughness. At a low sputtering pressure, a flat and uniform film surface comprising nano-sized isotropic islands was observed. The surface islands transited to an anisotropic spindle-like shape at pressure higher than 1.0 Pa. The spindle-shaped islands elongated along the CeO2 [110] or [1 1 ¯ 0] directions, constructing an interwoven surface morphology. The distinct surface morphology evolution was correlated with the change in the film strain state attributed to varying sputtering pressure. A possible mechanism for this morphology evolution was discussed.

In the present work, lead-free K 0.48 Na 0.52 NbO 3 (KNN) ceramics were synthesized by conventional ceramics processes. The excess 3.3 mol% Na 2 CO 3 and 1.1 mol% K 2 CO 3 were added to decrease the sintering temperature to 990 °C and effectively promote the densification of KNN ceramics. X-ray diffraction results indicated that the excess Na 2 CO 3 and K 2 CO 3 would induce the formation of the A-site riched secondary phase with the sintering temperature. Compositional segregation phenomenon enhanced by different sintering temperature, spurs the formation of secondary phase in KNN-AEe ceramics. In addition, the difference between ferroelectric domain structure of the poled and as-sintered KNN-AEe samples for 990 °C was investigated. Via XRD analysis and SEM observation, it was found that the domain orientation was urged during the poling process.

The oxygen content is one key factor to determine the properties of YBa 2 Cu 3 O 6+ y (YBCO) high temperature superconductors. In this study, YBCO thin films were produced by TFA-MOD method. The oxygenation process was carried out at 450 °C for 40 min, in various oxygen partial pressures from 0.01 to 1 atm. An in situ resistance measurement system was built up to record the resistance evolution during the whole heat treatment process. It was found that the resistance decreased exponentially and reached a saturate value in a few minutes during oxygen annealing. It was also found both the balanced resistance and the c -axis length of YBCO decreased with increasing oxygen partial pressure. A defect reaction was found to control the mechanism of the oxygenation process. A porosity assisted oxygen diffusion mechanism was proposed to explain the fast diffusion kinetics of oxygen in MOD YBCO thin films.

In this paper, lead-free (Na 0.474 K 0.474 Li 0.052 )(Nb 0.948 Sb 0.052 )O 3 ceramics were synthesized by a conventional solid-state reaction route. The effects of sintering temperature on the crystal structure, microstructure, densification, dielectric properties, and ferroelectric properties of the KNNLS ceramics were addressed. X-ray diffraction patterns and Raman spectrum indicated a transition from orthorhombic to tetragonal phase during the sintering temperature region. This transition is attributed to the migration of Li between the matrix grain and grain boundary. Scanning electron microscopy study revealed increased grain size and enhanced densification with increasing sintering temperature. The density of the ceramics sintered at 1080 °C reached a maximum value of 4.22 g/cm 3 . KNNLS ceramics sintered at an optimum temperature of 1080 °C exhibited high piezoelectric properties, that is 242 pC/N for d 33 , 0.42 for k p and 18.2 μC/cm 2 for P r .

Several kinds of phase structure change behavior in Li 0.058 (Na 0.51 K 0.49 ) 0.942 NbO 3 (KNNLN) ceramics were presented in this work. XPS measurement was employed to determine Na volatilization in the KNNLN samples, and this result explains the difference of the phase structure between the surface and interior of the samples. The phase structure of lead-free KNNLN piezoceramics are studied based on the measurements of the analysis of X-ray diffraction pattern and dielectric properties. The poled samples exhibit orthorhombic structure whereas the surface and interior for unpoled samples exhibit tetragonal and tetragonal-orthorhombic coexistent structures, respectively. An explanation to the mechanism of the structure transformation during poling processing was proposed.

Alumina ceramic is a high performance engineering material with excellent properties, including high melting point, high hardness and brittle nature make the alumina ceramic difficult to machine and needing high cost by using conventional manufacturing methods. Coating is an important method for alumina fabrication. The excellent properties of coatings can be used for special surface protection and ceramic parts repairing. Comparing with other coating methods, laser cladding method has many good properties to overcome the drawbacks. The reported investigations on laser cladding provide little information about alumina materials for ceramic coating. In this paper, effects of different input variables of laser cladding of alumina materials for ceramic coating were studied. And this paper for the first time reported the relationship between the properties (including surface roughness, flatness and powder efficiency) and input variables such as laser power, powder feeding rate and laser head moving rate. The obtained results will be helpful to establish efficient and effective processes for ceramics coating.

In present work, a simple and direct method was proposed, which could be applied for quantitatively calculating the percentage of 90° domain reorientation in the tetragonal phase of KNNLN ceramics. The relationship between 90° domain reorientation and poling field was established through the X-ray diffraction analysis. Experimental results indicate that the poling field of 5 kV/mm is sufficient for the reorientation of 90° domain and while the percentage of 90° domain reorientation 37.9% and piezoelectric constant 232 pC/N are obtained. The general trend of piezoelectric properties corresponds well with that of the percentage of 90° domain reorientation.

A novel approach to prepare dense AlN ceramics with high thermal conductivity was proposed. The aluminum isopropoxide (AIP) was introduced to prepare dense AlN ceramics possessing enhanced thermal conductivity via in situ reaction. The effect of AIP and sintering temperatures on the microstructure and properties of AlN ceramics were investigated. Results indicate that AIP is beneficial for the densification of AlN ceramics, and particularly, when the addition of AIP reaches 1 wt%, the density and thermal conductivity could reach up to 3.29 g/cm3, 182 W/mK, respectively. Finally, the mechanism of the in situ reaction was proposed.

Zr doped Ba0.6Sr0.4TiO3 ceramic was sintered by spark plasma sintering (SPS) and thermal treatment. Sintering behavior, microstructure and dielectric properties of the BST ceramics were investigated by XRD, SEM and impedance analyzer. High dense Ba0.6Sr0.4(Zr0.2Ti0.8)O3 ceramic with 98.2% of the theoretical density was fabricated at 1270 °C for 5 min. The dielectric constant of this sample reduced to 850 at 100 kHz, the tunability of the ceramic increased to 57% (1.5 kV/mm, 298 K) and the figure of merit (FOM) value increased to 475, which is promising material for tunable devices application.

The phase structure of lead-free Li 0.058 (Na 0.51 K 0.49 ) 0.942 NbO 3 (KNNLN) ceramics can be affected by the stress as well as the external electric field. A high piezoelectric constant was obtained in KNNLN ceramics by adjusting the cooling-down speed of the sintering. The {2 0 0} reflection X-ray diffraction lines were measured to accurately identify the room-temperature crystal structure of the as-sintered samples. Dielectric measurements were performed to observe the differences in the phase structure of KNNLN ceramics before and after poling.

In this study, Fe 2 O 3 and TiO 2 codoped Li 0.05 (Na 0.5 K 0.5 ) 0.95 (Nb 0.975 Sb 0.025 )O 3 [(1 − x ) Li 0.05 (Na 0.5 K 0.5 ) 0.95 (Nb 0.975 Sb 0.025 )O 3 – x (Fe 2 O 3 –2TiO 2 ) ( x = 0–0.008)] ceramics were prepared by conventional solid state reaction method, and the microstructure and electrical properties of these samples were investigated. The X-ray diffraction and Raman scattering results show the phase structure of the ceramics undergoes with the increase of Fe 2 O 3 –2TiO 2 content. The grain size distribution of non-doped Li 0.05 (Na 0.5 K 0.5 ) 0.95 (Nb 0.975 Sb 0.025 )O 3 ceramics was relatively wide. The microstructure was composed of grains ranging 0.2–3.0 μm in size. However, with increasing Fe 2 O 3 –2TiO 2 content, the grain size distribution became relatively narrow. Meanwhile, the piezoelectric coefficient ( d 33 ) and electromechanical coupling coefficient ( k p ) showed peak values of 252 pC/N, and 0.424, respectively, which were achieved in the sample with x = 0.002 sintered at 1020 °C.

The effects of sintering temperature and the addition of CuO on the microstructure and piezoelectric properties of 0.95(K0.5Na0.5)NbO3–0.05Li(Nb0.5Sb0.5)O3 were investigated. The KNN-5LNS ceramics doped with CuO were well sintered even at 940 °C. A small amount of Cu2+ was incorporated into the KNN-5LNS matrix ceramics and XRD patterns suggested that the Cu2+ ion could enter the A or B site of the perovskite unit cell and replace the Nb5+ or Li+ simultaneously. The study also showed that the introduction of CuO effectively reduced the sintering temperature and improved the electrical properties of KNN-5LNS. The high piezoelectric properties of d33 = 263 pC/N, kp = 0.42, Qm = 143 and tan δ = 0.024 were obtained from the 0.4 mol% CuO doped KNN-5LNS ceramics sintered at 980 °C for 2 h.

Lead-free (K0.462Na0.48Li0.058)1+xNbO3(0 ≤ x ≤ 0.03) ceramics with excessive alkaline elements were synthesized by conventional ceramics processes as functions of sintering temperatures and quantities of excess alkaline elements. X-ray diffraction results reveal a transformation from tetragonal phase to orthorhombic phase with increasing the contents of excessive alkaline elements. The grain size and the piezoelectric properties were enhanced when a certain amount of excessive alkaline elements were added. Further elevation in the amount of alkaline elements added resulted in excessive liquid phase in the ceramics and deteriorated the piezoelectric properties. With x = 0.01, the ceramics sintered at 1050 °C show better properties of planar electromechanical coupling factor kp = 43.4%, piezoelectric constant d33 = 204 pC/N, dielectric constant e 33 T / e 0 = 704.4 , and loss tangent tan δ = 2.8%.

Iron oxide particles with various shapes, sizes and phase concentrations (including α-Fe2O3 and Fe3O4) have been synthesized through a simple hydrothermal method in the ethylene glycol (EG)-water system. In the preparation conditions, ferric chloride (FeCl3·6H2O) was used as the iron source in the presence of sodium hydroxide (NaOH) without any surfactants. By adjusting the experimental parameters (EG/H2O ratio, base content, iron ions concentration, etc.), the shape, the size, the phase and the magnetic property of the products could be easily controlled. The products were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), and a vibrating sample magnetometer (VSM). A further investigation revealed that high EG content and high alkaline condition favored the formation of Fe3O4 phase. A possible growth mechanism was proposed based on the experimental results. The magnetic properties were deeply affected by the morphology and phase of the as-synthesized products. The controlled shape, size and phase structure of the iron oxides through simple synthetic procedures provides potential opportunities to realize the promising size and shape-dependent applications.

(NaxKy) (Nb0.885Sb0.08)–0.035LiTaO3 lead-free piezoelectric ceramics (NxKyNS–LT) with an excessive amount of Na or K were synthesized by conventional solid-state processes. Effects of Na/K ratio on structure and electrical properties of NxKyNS–LT ceramics were investigated. Excessive Na or K did not change the major crystal structure and barely influenced the sintering temperature, but excessive Na or K exhibited effects on grain size. Better piezoelectric properties of the ceramics were achieved when a certain amount of excessive K was added (the Na/K ratio before calcining was adjusted to 0.520:0.450). X-Ray fluorescence was used to examine the cause, and the enhanced properties are attributed to the formation of an MPB-like composition when the Na/K was changed. Specimens with properties of d33=183 pC/N, kp=0.33, Qm=103 were obtained in this work.

The 0.95(K0.5Na0.5NbO3)–0.05Li(Nb0.5Sb0.5)O3 doped with 0.8 mol% copper oxide (CuO) lead-free piezoelectric ceramics were synthesized by conventional solid-state reaction route. The introduction of CuO could significantly improve the sinterability of 0.95(K0.5Na0.5NbO3)–0.05Li(Nb0.5Sb0.5)O3 ceramics. The grain size of the specimen was considerably decreased due to the formation of a large amount of liquid phase when the sintering temperature exceeded 960°C. The piezoelectric constant (d33), planar electromechanical coupling (kp), and dielectric constant () values increased with increasing relative density and grain size. The improved piezoelectric and dielectric properties of d33=207 pC/N, kp=44%, tan δ=0.0137, Qm=320, and =340 can be obtained for specimens sintered at 960°C for 2 h.

Lead-free 0.94(K0.48Na0.535)NbO3–0.06LiNbO3–xmol%CuO ceramics were synthesized by conventional ceramics processes. The doping of CuO can decrease the sintering temperature to 890°C and effectively promote the densification of 0.94(K0.48Na0.535)NbO3–0.06LiNbO3 ceramics. X-ray diffraction result reveals that doping of CuO induces lattice distortion. Homogeneous grain growth is observed, due to the presence of liquid phase that resulted from the addition of CuO. The ceramics sintered at 890°C show fairly good properties with the planar electromechanical coupling factor kp=34.8%, piezoelectric constant d33=157.5 pC/N, dielectric constant ɛ33T/ɛ0=391, and mechanical quality factor Qm=173.5.

Plate-like Bi 5 Nb 3 O 15 (B5N3) particles and rectangular KNb 5 Bi 2 O 16 (KN5B2) particles were synthesized by the molten salt process and topochemical microcrystal conversion (TMC), respectively. The effects of the synthesis parameters on the phase structure and morphology of B5N3 precursor and KN5B2 were investigated. Results indicated that the retro-synthesis process of the as-synthesized KN5B2 retained the morphology and structural feature of the B5N3 precursor. The prepared KN5B2 particles with high aspect ratio of 20–30 are promising templates for texturing bismuth-layer and alkali niobate based ceramics by (reactive) templated grain growth method. The same method can be applied to other perovskite-structured templates.

In the present work, the dependence of microstructure and electrical properties on B-site non-stoichiometry (excess) for (Na0.474K0.474Li0.052)(Nb0.948Sb0.052)O3 − xTa2O5 (KNLNSTx) was symmetrically investigated. The phase structure was pure perovskite when x 0.02 mol, a secondary phase would be found in the samples. The results indicate that the densification and piezoelectricity were promoted as x < 0.01 mol. It is supposed that the low amount of Ta could induce A-site vacancy and favor the poling efficiency. KNLNSTx ceramics with x = 0.005 mol Ta2O5 have optimum electrical properties: d33 = 253 pC/N, kp = 0.437, Qm = 43 and tanδ = 0.027.

In this study, MgO thin films were deposited by radio-frequency magnetron sputtering. The film thickness in the deposition area directly facing the target center obviously decreased compared with that in other areas. This reduction in thickness could be attributed to the resputtering effect resulting from bombardment by energetic particles mainly comprising oxygen atoms and negative oxygen ions. The influences of deposition position and sputtering pressure on the deposition rate were investigated. Resputtering altered the orientation of the MgO film from (111) to (001) when the film was deposited on a single crystal yttria-stabilized zirconia substrate. The density distribution of energetic particles was calculated on the basis of the measured thicknesses of the MgO films deposited at different positions. The divergence angle of the energetic particle flux was estimated to be approximately 15°. The energetic particle flux might be similar to the assisting ion flux in the ion beam assisted deposition process and could affect the orientation of the MgO film growth.

Corrigendum to “Low-temperature sintering of KNN with excess alkaline elements and the study of its ferroelectric domain structure” [Curr. Appl. Phys. 13 (2013) 2082e2086] Yongjie Zhao *, Rongxia Huang *, Rongzheng Liu , Heping Zhou , Wei Zhao b a State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, People’s Republic of China b School of Materials Science and Engineering, Tianjin Institute of Urban Construction, Tianjin 300072, People’s Republic of China

In the reported low-fluorine MOD-YBCO studies, the lowest F/Ba mole ratio of the precursor solution was 4.5. However, further lowering the F/Ba ratio is important according to the researches of YBCO thick film. On the other hand, the F/Ba ratio is necessary to be at least 2 for the full conversion of the Ba precursor to BaF_2 to avoid the formation of BaCO_3, which is detrimental to the superconducting performance. In this study, a novel solution with the F/Ba mole ratio of 2 was developed, in which the fluorine content was only about 10.3% of that used in the conventional TFA-MOD method. Attenuated total reflectance-Fourier transformed-infrared spectra(ATR-FT-IR) revealed that BaCO_3 was remarkably suppressed in the as-pyrolyzed film and eliminated at 700 Celsius degree. Thus YBCO films with a critical current density (J_c) over 5 MA cm^{-2} (77 K, 0 T, 200 nm thickness) could be obtained on LAO single crystal substrates. In-situ FT-IR spectra showed that no obvious fluorinated gaseous by-products were detected in the pyrolysis step, which indicated that all of the F atoms might remain in the film as fluorides. X-ray diffraction (XRD) \theta/2\theta-scan showed that BaF_2, but neither YF_3 nor CuF_2, was detected in the films quenched at 400 - 800 Celsius degree. The formation priority of BaF_2 over YF_3 and CuF_2 was interpreted by the chemical equilibrium of the potential reactions. Our study could enlarge the synthesis window of the precursor solution for MOD-YBCO fabrication and open a gate to study the fluorine content in the precursor solution continuously and systematically.

During the fabrication of YBa2Cu3O7?? (YBCO) thin films via the metal organic deposition (MOD) method, the water content of the precursor solution should be reduced to prevent precipitation and other detriment. In most of the reported MOD-YBCO studies, water was used as a solvent, and vacuum distillation was utilized to reduce the water content of the precursor solution. In this study, we propose a water-free MOD method using propionic anhydride and methanol as the solvents. The crystal water of raw precursor salts was removed by heating, and the water content in the final precursor solution was as low as 0.2?wt%. Using this solution with low fluorine content and the optimized maximum temperature of pyrolysis, the final YBCO thin films about 250?nm thick had the critical current density (Jc) of 3.8?MA?cm?2 (77?K, self-field). The water content of the precursor solution was further reduced to less than 10?2?wt% by vacuum distillation. According to the Jc performance, thermal analysis, x-ray diffraction investigations, and morphology observations, no significant improvement was found for the final YBCO thin films fabricated by the distilled solution, indicating that vacuum distillation is not necessary in the water-free MOD method.

Trifluoroacetate metal–organic deposition (TFA-MOD) is a promising technique to fabricate YBa2Cu3O7−δ (YBCO) superconducting films. However, its slow pyrolysis process, which usually takes more than 10 h, constitutes a barrier for industrial production. In this study, polyethylene glycol (PEG) was utilized to reduce the stress generation inside the coated films when the strong pyrolysis reactions happen. With the addition of 30 wt% PEG2000 to the precursor solution, a smooth film surface could be obtained through a rapid pyrolysis process of 15 min. After the optimizations of the crystallization and oxygenation processes, mass percentage and molecular weight of PEG additive, YBCO thin films with Jc of about 4.5 MA cm−2 (77 K, self-field) could be routinely fabricated using (20–30) wt% PEG(1000–2000) additive with a total treatment time of about 2 h including the 15 min pyrolysis process time. The effects of PEG additive were discussed using one of the mechanisms of buckling formation. The reduction of compressive stress by PEG additive was suggested to be the reason for preventing buckling.

A general combined hydrothermal and annealing process for the fabrication of ferrite/perovskite oxide core/shell nanostructures was introduced. The coating of a perovskite oxide (ABO3) layer on spherical ferrite particles was performed in two steps. A dense and smooth amorphous layer containing B-site ions of the perovskite oxide was coated first via a controlled hydrolysis and aging process. During hydrothermal treatment and subsequent annealing process, the A-site ions were incorporated in situ into the as-coated amorphous layer preserving the spherical morphology. This synthesis of ferrite/perovskite oxide core/shell nanostructures was demonstrated in systems like Fe3O4/PbTiO3, γ-Fe2O3/PbTiO3, γ-Fe2O3/Pb(Zr,Ti)O3, CoFe2O4/BaTiO3, CoFe2O4/PbTiO3 and CoFe2O4/Pb(Zr,Ti)O3. This method allowed the shell thickness of the composite particles to be manipulated in a controlled manner with various core sizes. After the coating, the core and shell materials showed strong interactions and the ferroelectric layer dramatically affected the crystal structure, resistivity and magnetic properties of the composites.

Uniform magnetic Fe3O4 chains with an average length of 20 μm built up by tens of self-assembled microspheres have been synthesized via a simple surfactant-free hydrothermal method. A possible “nucleation-growth-connection-crystallization” growth mechanism has been proposed for the formation of the Fe3O4 chains.