The K x Na (1- x ) NbO 3 ( x = 0.45, 0.46, 0.47, 0.48, 0.49, 0.50) lead-free piezoelectric ceramics was fabricated by conventional solid-state sintering method. It was found that the ratio of alkaline metal would affect the microstructure, bulk density, and optimum sintering temperatures of ceramics. Meanwhile, the electrical properties were also influenced by modulating the K/Na ratio, exhibiting corresponding composition-dependent properties. The optimum electrical properties of K x Na (1- x ) NbO 3 such as piezoelectric constant d 33 = 115 pC/N, mechanical quality factor Q m = 20, Curie temperature T c = 365 °C, ε T 33 /ε 0 = 588.1, dielectric loss tan δ = 0.024, bulk density (ρ) = 3.08 g/cm 3 , remnant polarization ( P r ) = 8.87 μC/cm 2 and coercive field ( E c ) = 13.79 kV/cm were obtained at x = 0.46.

A direct liquid injection chemical vapor deposition was utilized to prepare Co3O4 films with a high deposition rate. All the Co3O4 films showed spinel crystalline structures of CoIICo2IIIO4. A (111)-orientation preferred Co3O4 film with scattered triangular grains and elongated nano-wall surface morphology was prepared at the deposition temperature (Tdep) of 773K, while randomly grown Co3O4 films with porous structures were found with lower or higher Tdep. The maximum deposition rate (Rdep) of Co3O4 films reached 3.6μmh−1, which was around 10 times higher than those previously reported by metal organic CVD method. With increasing Tdep, the color of Co3O4 films changed from light to black brown owing to the thickness difference.

CeO2 films were prepared at deposition temperature ranged from 947 to 1096 K (corresponding laser power was from 52 to 185 W) on (100) LaAlO3 single crystal substrate by laser chemical vapor deposition. At deposition temperature of 1027–1096 K (laser power was from 115 to 185 W), highly (100)‐oriented CeO2 films with wedge‐caped columnar grains were prepared, whose epitaxial growth relationship was CeO2 [100]//LAO [100] (CeO2 [010]//LAO [011]). Their full width at half maximum of the ω‐scan on the (200) reflection and that of the ϕ‐scan on the (220) reflection were 0.8°–1.8° and 0.7°–1.2°, respectively. The highest deposition rate at which CeO2 film with pure (100) preferred orientation could be obtained was 30 μm h−1.

YBa2Cu3O7−δ (YBCO) films were prepared at deposition rates ranging from 10 to 55μmh−1 on CeO2/LaMnO3/MgO/Gd2Zr2O7/Hastelloy C276 substrate by spray atomizing and coprecipitating laser chemical vapor deposition. At a deposition rate of 10μmh−1, a c-axis-oriented YBCO film with a high critical temperature (TC) of 91K and critical current density (JC) of 2.4MAcm−2 was prepared, which showed an epitaxial growth mode of YBCO [001]//CeO2 [100] (YBCO [100]//CeO2 [011]). The full width at half maximum (FWHM) of the ω-scan and that of the φ-scan of the YBCO film were 1.9° and 3.2°, respectively. At a deposition rate of 45μmh−1, an a-axis-oriented YBCO film with a TC of 78K and a JC of 0.4 MAcm−2 was obtained. The YBCO film showed an epitaxial growth mode of YBCO [100]//CeO2 [100] (YBCO [001]//CeO2 [011]) and had the FWHM of 4.9° for the ω-scan and that of 9.5° for the φ-scan, respectively.

Hierarchical micro- and nanoscale domain structures in Pb-free Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics were investigated by transmission electron microscopy. In situ heating and cooling studies of domain structure evolution reveal an irreversible domain transformation from a wedge-shaped rhombohedral nanodomain structure to a lamellar tetragonal domain structure, which could be associated with strong piezoelectricity in Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 piezoceramics.

0.94Na0.5Bi0.5TiO3–0.06BaTiO3 lead-free ceramics were fabricated by templated grain growth method using 5vol% platelet Bi4Ti3O12 (BIT) templates. The effect of the addition of excess Bi2O3 on the densification and the texture evolution was investigated. A high degree of grain orientation (f∼0.93) and an excellent piezoelectric coefficient d33 of ∼290pC/N were obtained for undoped samples, however the texture was hardly developed for Bi2O3 doped samples whose densification behavior yet could be significantly improved. It was found that the Bi2O3 liquid phase can promote the particle rearrangement and mass transport, but simultaneously change the surface morphology of BIT templates and matrix grains from an atomically rough to smooth structure. The Ostwald growth was thus induced dominantly in the diametrical direction and little in the thickness direction of plate-like templates. The results provided a good reference for selecting the sintering aid in the fabrication of textured ceramics.

The (111) oriented plate‐like BaTiO3 (BT) particles with a tetragonal perovskite structure and a stoichiometric composition were successfully synthesized by a two‐step molten‐salt synthesis method (MSS). The as‐synthesized BT particles preserved the plate‐like shape of precursor Ba6Ti17O40 (B6T17) particles with (001) major crystalline face, and, however, had a preferred pseudo‐cubic (111) orientation. BT particle with a high aspect ratio (10–20 μm in diameter and <1.5 μm in thickness) was achieved as the soaking temperature and time were optimized to be 1170°C and 5 h, respectively. Oriented particulate layer X‐ray diffraction analysis revealed that the crystallographic (001) plane of B6T17 has a topotactic relation with the (111) plane of BT particles.

Two-step molten salt driven micrometer-scaled tabular (100) BaTiO3 (BT) template seeds were used for the first time to make 〈100〉 textured 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 (NBT–BT) piezoelectric ceramics. The use of platelet Bi4Ti3O12 powders instead of Bi2O3 and TiO2 as raw chemicals would not only benefit to the alignment of BT templates during tape casting, but also avoid the dissolution of BT seeds in liquid Bi2O3 during sintering. The results also proved that a pre-reaction procedure at a low temperature is unnecessary during reactive templated grain growth owing to the structure similarity between BT seeds and target compound. Well-textured NBT–BT lead-free piezoelectric ceramics (f∼91%) show excellent dielectric and piezoelectric properties of dielectric constant ɛr∼1300 and piezoelectric charge constant d33=260pC/N.

Two-step pressureless sintering of sol–gel derived 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 (BNT-BT) lead-free piezoelectric ceramics were investigated in comparison with conventional sintering. The effect of sintering regimes on the densification, grain growth behavior and electrical properties was discussed in detail. The results indicated that BNT-BT ceramics with a density of 95%, a relatively fine grain size of 850 nm and comparable piezoelectric properties (d33 ~170 pC/N, kp ~0.26, Qm ~102) had been achieved by pre-sintering at 1,150 °C to reach a critical density of 78%, and then cooling to a lower temperature of 1,050 °C for 20 h. The critical density value proves important at which the grain boundary diffusion could be maintained but the grain boundary migration suppressed at the same time. Moreover, the volatilization loss of Bi and Na elements could be inhibited by two-step sintering. Both the reduction of the grain size and the inhibition of the stoichiometry deviation together account for the variation of various electrical properties.

(Na0.5K0.5)NbO3 (KNN) ceramics with {100} orientation without sintering aids were fabricated by a conventional process and reactive templated grain growth using tabular NaNbO3 template particles. The KNN specimen sintered at 1,170 °C for 15 h were found to have a relative density of 95.6%. The experimental results show that the textured ceramics have a pseudo-cubic {100} orientation degree of 96.2% and a microstructure with brick-like grains aligning in the direction parallel to the casting plane. The dielectric constant is much higher than the value for non-textured ceramics. Transition temperatures (T o–t, T c) are reduced and dielectric peaks are greater breadth. Remanent polarization P r decreased from 19.40 (the random KNN) to 13.77 (textured KNN) μC/cm2. The textured ceramics show anisotropic electrical properties between different directions of textured KNN ceramics, and show a very high electromechanical coupling factor k p = 0.58 and a high piezoelectric constant d 33 = 225 pC/N, compared to the random counterparts (k p = 0.31, d 33 = 115 pC/N).

Poling dependence and stability of piezoelectric properties of lead-free 0.5Ba(Zr0.2Ti0.8)O-3-0.5(Ba0.7Ca0.3) TiO3 ceramics were investigated. The experimental results indicated that the poling condition has an obvious effect on the piezoelectric properties due to the existence of a phase transition near room temperature. The best piezoelectric coefficient d(33) and planar electromechanical coupling factor k(p) could reach 630 pC/N and 56%, respectively as the poling conditions were optimized. However, these properties exhibit strong temperature and time dependences, owing to a rather low depolarization temperature (below 80-90 degrees C) and extremely high aging rate (30% and 25% loss for d(33) and k(p), respectively, 10(4) min after poling). (C) 2011 Elsevier B.V. All rights reserved.

New lead-free piezoelectric ceramics (1-x)(Na0.5K0.5)NbO3-xBa(Ti0.95Hf0.05)O-3(NKN-xBTH) doped with 0.8 mol.% CuO have been successfully fabricated by traditional solid state sintering. Owing to complex atomic occupation at A-sites and B-sites, the ferroelectric phase transition of NKN becomes more and more diffuse with increasing BTH content. On the other hand, it was found that the addition of a small amount of BTH shifts an orthorhombic-tetragonal polymorphic phase transformation of pure NKN composition downwards to room temperature. The two-phase transition zone was identified approximately at 0.04 < x < 0.06 and the ceramic with x = 0.06 possesses obviously enhanced electrical properties: d(33) = 185 pC/N, k(p) = 0.38, epsilon(T)(33) = 1690, Q(m) = 108 and T-c = 267 degrees C, compared to pure NKN.

A sol–gel method was used to prepare CaO–B2O3–SiO2 (CBS) glass powder for making low-temperature cofired ceramics. This paper was focused on the mechanism of hydrolysis and polymerization and also on the structural evolution of xerogel at various temperatures. The xerogel was transformed into glass ceramics containing CaSiO3 and CaB2O4 crystalline phases through nucleation and crystallization processes. The results indicated that the xerogel exhibits [BO4] or [SiO4] based three-dimensional network structure whose interstices Ca ions fill in, which becomes more orderly and stable after heat treatments. The CBS glass ceramics through controlled crystallization have a potential as electronic packaging materials.

Two-step pressureless sintering of sol–gel derived 0.94(BiNa)TiO–0.06BaTiO (BNT-BT) lead-free piezoelectric ceramics were investigated in comparison with conventional sintering. The effect of sintering regimes on the densification, grain growth behavior and electrical properties was discussed in detail. The results indicated that BNT-BT ceramics with a density of 95%, a relatively fine grain size of 850 nm and comparable piezoelectric properties (d ~170 pC/N, k ~0.26, Q ~102) had been achieved by pre-sintering at 1,150 °C to reach a critical density of 78%, and then cooling to a lower temperature of 1,050 °C for 20 h. The critical density value proves important at which the grain boundary diffusion could be maintained but the grain boundary migration suppressed at the same time. Moreover, the volatilization loss of Bi and Na elements could be inhibited by two-step sintering. Both the reduction of the grain size and the inhibition of the stoichiometry deviation together account for the variation of various electrical properties.

The solid solutions of (1−x)Pb(Zr0.56Ti0.44)O3–xBi(Zn0.5Ti0.5)O3 ((1−x)PZ56T44–xBZT) were synthesized via a solid‐state reaction method. X‐ray diffraction results indicated that the tetragonality of (1−x)PZ56T44–xBZT was enhanced with increasing the BZT content, and a morphotropic phase boundary (MPB) between rhombohedral and tetragonal ferroelectric phases was identified to be in the range of 0.15 < x < 0.18. In addition, the dielectric diffuseness and frequency dispersion behavior were induced with increasing the BZT content, owing to increased disorder degree of both A‐site and B‐site cations in (1−x)PZ56T44–xBZT perovskite lattice. Contrary to the case in PT–BZT, the increased tetragonality accompanies reduced Curie temperatures (Tc) as PZ56T44 was substituted by BZT. The electrical properties of solid solutions exhibit obviously compositional dependence. The optimum dielectric and piezoelectric properties of = 1430, d33 = 365 pC/N, kp = 50%, Qm = 32, and Tc = 260°C were achieved in (1−x)PZ56T44–xBZT ceramics with x = 0.18 owing to the co‐existence of two ferroelectric phases near the MPB.

Micrometer-sized (001) oriented BaTiO3 (BT) platelets with a perovskite structure, a stoichiometric composition and a high aspect ratio (10–20μm in diameter and 0.5–1μm in thickness) were synthesized through a modified two-step molten salt method by means of a typical topochemical microcrystal conversion. The results indicated that it is necessary to prevent Bi+ and Cl− or NO3− from coexisting under nonacidic or weakly acid environment. A less pollutive washing method and the corresponding principle were summarized in combination with the hydrolysis reaction process. The effect of synthesis temperatures on the formation of BT platelets was discussed.

The CuO modified (Na0.52K0.48)NbO3 (NKN) piezoelectric ceramics were prepared by a solid-state reaction method. On the one hand, CuO doping can improve the densification behavior and simultaneously promote the grain growth, however, has little effect on the Curie temperature. On the other hand, the mechanical quality factor Q(m) obviously increases, the dielectric loss tan delta decreases, and the piezoelectric constant (133 and the planar electromechanical coupling coefficient k(p) tend to drop. Moreover, an obvious effect comes from the sintering conditions. The 1 mol% CuO doped NKN ceramics sintered at 1090 degrees C for 3 h own the electrical properties: Q(m) = 1727, tan delta = 0.29%. d(33) = 74 pC/N, k(p) = 0.22 and a dielectric constant epsilon(r) = 410. All these effects of CuO doping are considered to result from the liquid phase and oxygen vacancies formed during sintering.

Solid solutions of (Na0.5K0.5)NbO3 (NKN) and Li(Ta0.5Nb0.5)O3 (LTN) were investigated as a potential candidate of lead-free piezoelectric ceramics. It was found that the Curie temperature of solid solutions increases slightly with increasing the LTN content and simultaneously the polymorphic phase transition temperature linearly decrease till below room temperature. An orthorhombic to tetragonal phase transformation at room temperature, or a morphotropic phase boundary, in NKN is induced by ~7 at% LTN addition, where the best dielectric, piezoelectric and electromechanical properties are achieved. The 0.94NKN–0.07LTN ceramics possess a dielectric constant of 765, a loss tangent of 0.04 at 1 kHz, a piezoelectric constant d33 of 253 pC/N and an electromechanical coupling factor kp of 48%.