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PbTiO3 (PT) microstructures were fabricated by topochemical microcrystal conversion (TMC) and their morphological evolution was investigated with variation of synthesis temperature and relative molar ratio of reactants. Using molten salt synthesis, Aurivillius phase of PbBi4Ti4O15 (PBiT) synthesized at 1050°C was prepared as precursor. Large plate‐like PT microstructures with lengths of hundreds of micrometer were optimally obtained when the relative ratio (x) of (PbCO3)2·Pb(OH)2 to PBiT in reactants was 6. In addition, relatively homogeneous PT platelets were achieved at the annealing temperature of 1050°C by TMC; these materials are probably suitable for use in templated grain growth. However, a Pb‐deficient secondary phase of PbTi3O7 formed in cases of low x values of less than 4 and low annealing temperatures of less than 1050°C. The porous PT pellets, orthogonally assembled by numerous PT platelets, were achieved by increasing temperature to 1100°C. Further increase in temperature to 1150°C could lead to partial formation of denser PT blocks. [ABSTRACT FROM AUTHOR]

Bi-Te is a thermoelectric material used at room temperature. It is typically fabricated as a single-crystal ingot, making processing difficult and material loss very high. Pressureless sintering processes have been studied to address these issues; however, they typically result in lower-density material. Methods such as hot isostatic pressing and spark plasma sintering have mainly been studied. However, there has been limited research on pressureless sintering without additional steps such as pressurization or charging. The aim of this study is to obtain a dense Bi2Te2.7Se0.3 sintered body by combining rapid sintering with air sintering by modifying a typical sintering furnace. The effect of heating rate on densification and phase change was also investigated. Bi2Te2.7Se0.3 powder was first synthesized by the mechanochemical method. The synthesized powder was then heated at a rate of 5°C/s to 20°C/s and finally sintered at a temperature of 570°C for 10 min in H2/N2 mixture under Te-rich conditions. These conditions produced a sintered body with relative density of at least 90% of the theoretical density, and a bulk density of 6.98 g/cm3 was obtained when temperature was increased at a rate of 20°C/s. Observation of the microstructure showed that porosity decreased as the heating rate was increased. The results of this study confirm that the heating rate during rapid sintering can affect the density of the sintered body. [ABSTRACT FROM AUTHOR]

We present a general rule for the perovskite oxide ceramics: “A large piezoelectric constant in ABO3 perovskite ceramics can be obtained by tuning the weight ratio of A and B sites, WA/WB or WB/WA, to 3. Piezoelectric constant decreases significantly when WA/WB or WB/WA is in the range of 0.5–2.0, termed as forbidden zone.” A comparative analysis was conducted for broad range of materials demonstrating the applicability of proposed rule. Further based on this rule optimized compositions in BaTiO3 and alkali niobate based systems were developed. Polycrystalline ceramics in modified BaTiO3 system were found to exhibit longitudinal piezoelectric coefficient (d33) of 330 pC/N, while alkali niobate ceramics showed d33 of 294 pC/N. [ABSTRACT FROM AUTHOR]

The presence of the Sb5+ ion increased the piezoelectric properties of the (Na0.5K0.5)NbO3 (NKN) ceramics by enhancing the poling state as identified by the increased phase angle (θ). The increased θ value was explained by the increased ferroelectricity due to the large electronegativity of the Sb5+ ion and the increased off centering of the cation due to the small ionic size of the Sb5+ ion. The (Na0.5K0.5)(Nb0.97Sb0.03)O3[NK(N0.97S0.03)] ceramics containing CuO were well sintered even at 960 °C. A small amount of the Cu2+ ions was incorporated into the matrix of the NK(N0.97S0.03) ceramic and behaved as a hardener. The kp, Qm, d33, and [variant_greek_epsilon]3T/[variant_greek_epsilon]0 values of the CuO-added NK(N0.97S0.03) ceramics were much higher than those of the CuO-added NKN ceramics due to the Sb5+ ion’s enhancement of the piezoelectric properties by increasing the poling state of the specimens. The high piezoelectric properties of kp=0.41, Qm=1333, d33=111 pC/N, and [variant_greek_epsilon]3T/[variant_greek_epsilon]0=324 were obtained from the 2.0 mol % CuO-added NK(N0.97S0.03) ceramics sintered at 960 °C for 8 h. [ABSTRACT FROM AUTHOR]

The crystal structure of (1-x)(Na0.5K0.5)NbO3-xCaTiO3 ceramics began to change from orthorhombic to tetragonal at x≥0.03, then became a morphotropic phase boundary in which both the orthogonal and tetragonal phases coexisted at 0.0333=241, kp=0.41, and [variant_greek_epsilon]3T/[variant_greek_epsilon]o=1316 were obtained from the 0.95NKN-0.05CT ceramics sintered at 1050 °C for 2 h, indicating that the 0.95NKN-0.05 ceramic is a good candidate material for lead-free piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Bi12GeO20 ceramics sintered at 800°C had dense microstructures, with an average grain size of 1.5 lm, a relative permittivity (∊r) of 36.97, temperature coefficient of resonance frequency (τƒ) of - 32.803 ppm/°C, and quality factor (Q × ƒ) of 3137 GHz. The Bi12-xGeO20-1.5x ceramics were well sintered at both 800°C and 825°C, with average grain sizes exceeding 100 µm for x ≤ 1.0. However, the grain size decreased for x > 1.0 because of the Bi4Ge3O12 secondary phase that formed at the grain boundaries. Bi12-xGeO20-1.5x (x ≤ 1.0) ceramics showed increased Q × ƒ values of >10 000 GHz, although the er and sf values were similar to those of Bi12GeO20 ceramics. The increased Q × ƒ value resulted from the increased grain size. In particular, the Bi11.6GeO19.4 ceramic sintered at 825°C for 3 h showed good microwave dielectric properties of ∊r = 37.81, τƒ = - 33.839 ppm/°C, and Q × ƒ = 14 455 GHz. [ABSTRACT FROM AUTHOR]

Microstructural and piezoelectric properties of 0.72Pb(Zr1-xTix)-0.28Pb(Zn0.4Ni0.6)1/3Nb2/3O3 (PZ1-xTx-PZNN) ceramics with 0.50 ≤ x ≤ 0.55 were investigated for evaluating the possibility of their use in multilayer actuators and energy harvesters, which demand a large piezoelectric strain constant (d33) and a small dielectric constant (εT33/εo). The PZ0.47T0.53-PZNN ceramic with a morphotropic phase boundary (MPB) composition showed large d33 and εT33/εo values, making it unsuitable for use in multilayer actuators and energy harvesters. However, the PZ0.48T0.52-PZNN ceramic with a rhombohedral structure showed a small εT33/εo value of 1605, yet maintained a large d33 of 550 pC/N. Thermal stimulation did not have any significant effect on the piezoelectric properties of this specimen, except for a slight increase in the εT33/εo value upon heating the specimen at 150°C for 4 h. In an effort to reduce the sintering temperature, CuO was used as an additive for the ceramic. As a result, the CuO-added PZ0.48T0.52-PZNN ceramic was well sintered at 900°C. In particular, the 1.0 mol% CuO-added PZ0.48T0.52-PZNN ceramic exhibited a large d33 value of 554 pC/N and a small εT33/εo value of 1620, making it highly suitable for use in multilayer actuators and energy harvesters. [ABSTRACT FROM AUTHOR]

A composite material with anisotropic microstructure was fabricated by DC electric field. Alumina was used as filler for thermal conductivity and polysiloxane resin was used as matrix. According to the alumina morphology and loading amount, various anisotropic microstructures were assembled. The thermal properties of the composite material were investigated parallel to the direction of the applied electric field accordingly. For plate-like alumina with 20 vol% loading, a thermal conductivity of 0.44 W/mK was achieved. With spherically shaped alumina, with an equal loading of 20 vol%, a higher thermal conductivity of 0.46 W/mK was achieved. The increase in the thermal conductivity of the fabricated alumina composites with anisotropic microstructure was attributed to increased filler-to-filler connectivity. [ABSTRACT FROM AUTHOR]

The microstructural properties and the chemical compositions of a 0.65 Pb( Zr0.42 Ti0.58) O3-0.35 Pb( Ni1/3 Nb2/3) O3 (0.65 PZT58-0.35 PNN) ceramic system sintered at 900°C for 4 h with 10 mol% CuO additives were studied using transmission electron microscope ( TEM) and energy dispersive spectroscopy ( EDS). CuO pockets were found as new microstructural constituents. The liquid phase has formed by the partial melting of CuO additives at the sintering temperature by reacting with Pb element in the matrix. The reaction started at the interfaces and then proceeded into the pocket through the diffusion of the Pb element. The presence of the Pb-rich precipitates during cooling was confirmed by EDS analyses. Cu-rich crystals in the pocket were observed near the boundaries between the matrix grain and the pocket. Rather smaller Pb- Cu- O-contained particle segments were detected around the center of the pocket, demonstrating that the reaction of melting of CuO has occurred with the Pb element which was diffused from the matrix. Due to the existence of the liquid phase, a dense microstructure was achieved during the sintering process and abnormal grain growth occurred in the process. [ABSTRACT FROM AUTHOR]

The article focuses on the effect that particle size distribution has on the piezoelectric properties and microstructure of manganese oxide ceramics. It states that the sintered density was enhanced by a high volume fraction of small-sized particles. It mentions that a green body's packing density has a direct influence on sintering and that the packing density is dependent on the mixture's ratio of large and small particles. It suggests that by using particles only smaller than 0.3 µm that higher piezoelectric properties could be attained.

When a small amount of CuO was added to (Na0.5K0.5)NbO3 (NKN) ceramics sintered at 960°C for 2 h, a dense microstructure with increased grains was developed, probably due to liquid-phase sintering. The Curie temperature slightly increased when CuO exceeded 1.5 mol%. The Cu2+ ion was considered to have replaced the Nb5+ ion and acted as a hardener, which increased the Ec and Qm values of the NKN ceramics. High piezoelectric properties of kp=0.37, Qm=844, and ℇ3 T/ℇ0=229 were obtained from the specimen containing 1.5 mol% of CuO sintered at 960°C for 2 h. [ABSTRACT FROM AUTHOR]

Microstructural characterizations using transmission electron microscopy on 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 ceramics sintered at 1030°–1150°C for 2 h were carried out. The liquid phase was found at the triple junction of the grains in all specimens and abnormal grain growth occurred in the presence of the liquid phase. Abnormally grown grains whose shapes were cuboidal were well developed. Anisotropically faceted amorphous liquid phase pockets were observed inside the grain in a specimen sintered at 1060°C for 2 h. The interface between the grain and the liquid matrix was flat and some were identified to be {100} planes of the grains. A certain amount of liquid at the sintering temperature of 1060°C enhanced the abnormal grain growth and contributed to the improvement of the piezoelectric properties. [ABSTRACT FROM AUTHOR]

The effect of TiO2 on microstructure and microwave dielectric properties of Ba(Zn1/3Ta2/3)O3 (BZT) ceramics was investigated. The addition of TiO2 did not disturb the 1:2 ordering structure of the BZT ceramic. The average grain size significantly increased with the addition of TiO2, which was attributed to the liquid phase formation. A small amount of TiO2 increased the relative density. However, relative density decreased with the addition of the large amount of TiO2 and it might be due to the abnormal grain growth. The Q value of the BZT significantly improved with the addition of the TiO2 for the specimens sintered at 1580 °C and it could be explained by the increased relative density. However, for the specimens sintered at 1630 °C, Q value decreased with the addition of the TiO2 which is attributed to the decrease of the relative density. The maximum Q×f value achieved in this investigation was about 135,000 GHz for the BZT with 1.0 mol.% TiO2 sintered at 1580 °C for 10 h. [Copyright &y& Elsevier]

Discusses the microstructural characterization on the LTLA dielectric ceramic system, conducted using transmission electron microscopy. Confirmation of the ordering due to the A-site vacancies by the presence of antiphase boundaries and superlattice reflection; Demonstration of the tilting of oxygen octahedra by the presence of the ferroelastic domains in the matrix.

Investigates the crystal structure of the (Ba[sub1-x]La[subx])[Mg[sub(1+x)/3]Nb[(2-x)/3]O[sub3] (BLMN) (0.9 ≤ x ≤ 1.0.), by using Rietveld refinement. Properties of lanthanum magnesium niobate (LMN); Description of the BLMN system; Illustration of a typical microstructure of LMN consisting of ordered domains and ferroelastic domains; Information on the five possibilities in selecting the phases involved in the BLMN system.

For 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 (0.95NKN-0.05BT) ceramics sintered at 1040–1075 °C, abnormal grain growth occurred but the grain size decreased when the sintering temperature exceeded 1075 °C. The dielectric constant (ε3T/ε3), electromechanical coupling factor (kp), and piezoelectric constant (d33) were considerably increased with increasing relative density and grain size. Evaporation of Na2O deteriorated the piezoelectric properties by decreasing the resistivity. To minimize Na2O evaporation, specimens were muffled with 0.95NKN-0.05BT powders during the sintering. Improved piezoelectric properties of d33=225 pC/N, kp=36%, and ε3T/ε3=1058 were obtained for specimen sintered at 1060 °C for 2 h with muffling. [ABSTRACT FROM AUTHOR]

KNbO3 (KN) nanowires were synthesized using various process conditions and their structures and morphologies were investigated. Homogeneous KN nanowires were formed in specimens synthesized at 130 °C for 24.0-48.0 h. These KN nanowires have a tetragonal structure that is known to be stable at high temperatures in the range of 225-435 °C. Tetragonal KN nanowires changed to orthorhombic KN nanoplates when the process time increased and homogeneous orthorhombic KN nanoplates existed for specimens synthesized for 144.0 h. In addition, tetragonal and orthorhombic structures coexisted in KN nanoplates synthesized at 130 °C for 72.0 h. For specimens synthesized at 100 °C, a long process time of 144.0 h was required to develop homogeneous KN nanowires that were also considered to have both tetragonal and orthorhombic structures. On the other hand, for specimens synthesized at 150 °C for 8.0 h, KN nanowires and a cube-shaped KN phase coexisted. Furthermore, a K4Nb6O17 second phase was formed in specimens synthesized for short periods of time (<8.0 h), indicating that the formation of homogeneous KN nanowires is difficult at 150 °C. Therefore, homogeneous KN nanowires with a tetragonal structure can be obtained at a low temperature of 130 °C with a short process time in the range of 24.0-48.0 h. [ABSTRACT FROM AUTHOR]

SiAlON ceramics are primarily employed in ceramic cutting tools, which exploit their stable physical properties in high-temperature cutting environments due to their excellent mechanical properties. Here, Yb/Y-co-doped SiAlON ceramics are prepared by adding Yb and Y rare-earth (RE) ions in the RE x Si 12-(m + n) Al m + n O n N 16- n (m = 0.4, n = 1.0) composition. Yb 2 O 3 , the RE oxide, is the main sintering additive. For RE x composition design with (Yb 1- y + Y y) x , Yb 2 O 3 is replaced by Y 2 O 3 (y = 0.00, 0.25, 0.50, 0.75, 1.00). While Yb 2 O 3 has excellent high-temperature stability, it is limited by its microstructural characteristics, that is, the β-SiAlON morphology and limited fracture toughness due to the small cation sizes. Thus, the changes in the above properties are investigated for various Y 2 O 3 additive contents substituting for Yb 2 O 3. The average grain width decreases, and the equiaxed β-SiAlON grains are elongated with increasing Y 2 O 3 content. Regarding the mechanical properties, the hardness and fracture toughness are evaluated using the indentation fracture method. The hardness decreases with increasing Y 2 O 3 content; however, the fracture toughness exhibits a significant increase (∼53.6%) from 4.6 to 7.0 MPa⋅m1/2. Regarding crack propagation, intergranular fracture is mainly observed in the Yb/Y-co-doped SiAlON ceramics, whereas transgranular fracture is primarily observed in the Yb-single-doped SiAlON ceramic. Y 2 O 3 substitution increases the α/β-SiAlON phase ratio, and the grain boundary phase exhibits increasing vitrification with increasing Y 2 O 3 content. Moreover, the thermal properties of the Yb/Y-co-doped compositions are analyzed and discussed regarding intrinsic properties such as phonon scattering. The microstructural characteristics and improved fracture toughness derived from the Yb/Y-co-doped system designed in this study suggest considerable potential for the future composition design of ceramic cutting tools. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate the correlation between sintering behavior and microstructural observations in low-temperature sintered, LaNbO4 microwave ceramics. Small CuO additions to LaNbO4 significantly lowered the sintering temperature from 1250 to 950°C. To elucidate the sintering mechanism, the internal microstructure of the sample manipulated by a focused ion beam (FIB) was investigated using transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS). LaNbO4 with 3wt% CuO sintered at 950°C for 2h possessed the following excellent microwave dielectric properties: a quality factor (Qxf) of 49,000GHz, relative dielectric constant (ɛ r) of 19.5, and temperature coefficient of resonant frequency (τ f) of 1ppm/°C. The ferroelastic phase transformation was also investigated using in situ X-ray diffraction (XRD) to explain the variation of τ f in low-temperature sintered LaNbO4 as a function of CuO content. [Copyright &y& Elsevier]

Abstract: A dense microstructure was developed for the 0.95(Na0.5K0.5)NbO3–0.05BaTiO3 (0.95NKN–0.05BT) ceramics sintered at above 1050°C. Grain growth was observed in the specimens sintered at 1050–1060°C while a liquid phase was found in the specimens sintered at above 1050°C, which explained the increased sinterability and grain size. KTiNbO5 and Ba6Ti2Nb8O30 second phases were also observed for the specimens sintered at above 1060°C. Evaporation of Na2O was responsible for the formation of the liquid phase and the KTiNbO5 and Ba6Ti2Nb8O30 second phases. Muffling with 0.95NKN–0.05BT powders during the sintering improved the piezoelectric properties, possibly due to the increased poling efficiency resulting from the reduced Na2O evaporation. [Copyright &y& Elsevier]

Abstract: The effect of B2O3 and CuO on the sintering temperature and microwave dielectric properties of BaSm2Ti4O12 ceramics was investigated. The BaSm2Ti4O12 ceramics were able to be sintered at 1000°C when B2O3 was added. This decrease in the sintering temperature of the BaSm2Ti4O12 ceramics upon the addition of B2O3 is attributed to the BaB4O7 second phase, whose melting temperature is around 900°C. The B2O3 added BaSm2Ti4O12 ceramics alone were not able to be sintered below 1000°C, but were sintered at 875°C when CuO was added. BaCu(B2O5) second phase might be responsible for the decrease in the sintering temperature of the CuO and B2O3 added BaSm2Ti4O12 ceramics. The BaSm2Ti4O12 +10.0mol% B2O3 +20.0mol% CuO ceramics sintered at 875°C for 2h have good microwave dielectric properties of ɛ r =61.47, Q × f =4256GHz and τ f =−9.25ppm/°C. The BaCu(B2O5) is also a good additive for decreasing the sintering temperature of the BaSm2Ti4O12 ceramics. [Copyright &y& Elsevier]

Abstract: The B2O3 added Ba(Zn1/3Nb2/3)O3 (BBZN) ceramic was sintered at 900°C. BaB4O7, BaB2O4, and BaNb2O6 second phases were found in the BBZN ceramic. Since BaB4O7 and BaB2O4 second phases have an eutectic temperature around 900°C, they might exist as the liquid phase during sintering at 900°C and assist the densification of the BZN ceramics. Microwave dielectric properties of dielectric constant (ɛ r )=32, Q × f =3500GHz, and temperature coefficient of resonance frequency (τ f )=20ppm/°C were obtained for the BZN with 5.0mol% B2O3 sintered at 900°C for 2h. The BBZN ceramics were not sintered below 900°C and the microwave dielectric properties of the BBZN ceramics sintered at 900°C were very low. However, when CuO was added, BBZN ceramic was well sintered even at 875°C. The liquid phase related to the BaCu(B2O5) second phase could be responsible for the decrease of sintering temperature. Good microwave dielectric properties of ɛ r =36, Q × f =19,000GHz and τ f =21ppm/°C can be obtained for CuO doped BBZN ceramics sintered at 875°C for 2h. [Copyright &y& Elsevier]

Abstract: B2O3 added Ba(Mg1/3Nb2/3)O3 (BBMN) ceramics cannot be sintered below 930°C. However, when CuO was added to them, they were sintered even at 850°C. The amount of the Ba2B2O5 second phase, which was formed in the BBMN ceramics decreased with the addition of CuO. Therefore, the CuO additive is considered to react with the B2O3 inhibiting the reaction between B2O3 and BaO. A dense microstructure without pores developed with the addition of a small amount of CuO. The bulk density, dielectric constant (ɛ r) and Q-value increased with the addition of CuO, but decreased when a large amount of CuO was added. Excellent microwave dielectric properties were obtained for the Ba(Mg1/3Nb2/3)O3 +2.0mol% B2O3 +10.0mol% CuO ceramic sintered at 875°C for 2h, with values Q xf =21500GHz, ɛ r =31 and temperature coefficient of resonance frequency (τ f)=21.3ppm/°C. [Copyright &y& Elsevier]

Li 2 O/B 2 O 3 -added Ba 1-x Sr x TiO 3 (B 1-x S x T) ceramics, where 0.2 ≤ x ≤ 0.35, were well densified at 920 °C with pure perovskite structure. The dielectric constant, tunability, and figure of merit (FOM) of B 1-x S x T ceramics increased with x because of the decreasing Curie temperature (T C). The specimen with x = 0.35, whose T C was close to room temperature, exhibited a large tunability of 27.4 % and FOM of 110 at 10 kV/cm. A compositionally graded multilayer (CGML), which was sintered at 920 °C, was fabricated using B 1-x S x T thick films to produce a temperature-stable tunable capacitor, and it evinced a dense microstructure and a continuous interface between the B 1-x S x T thick film and the Ag electrode. This CGML capacitor showed a large tunability (51 %) and FOM (150) at 20 kV/cm. It also exhibited stable tunability (17–28 % at 10 kV/cm) at temperatures between 30–90 °C. Therefore, the B 1-x S x T CGML capacitor is a suitable candidate for temperature-stable tunable capacitors. [ABSTRACT FROM AUTHOR]

It is well-known that the chemical modification of (K,Na)NbO 3 (KNN)-based ceramics (KNNs) by the addition of Bi 2 O 3 , or other aliovalent ions could decrease grain size and increases the crystal isotropic nature, namely, the pseudo-cubic phase since the sintered specimens could be transparent. However, due to the small grain size and pseudo-cubic phase, the transparent specimens have low piezoelectric properties. For obtaining better transparent and piezoelectric properties simultaneously, the starting KNNs composition must be selected with small grain size and high piezoelectric properties for Bi 2 O 3 modification. In this study, a high transmittance 52 % was measured at the wavelength of 800 nm, simultaneously with large piezoelectric constant (d 33 = 125 pC/N) by normal sintering method in KNLTN + 1.5 mol.% Bi 2 O 3 composition. The origin of high transmittance simultaneously with large piezoelectric constant might be due to the small reduction in grain size, owing to the small grain size of starting KNLTN composition. [ABSTRACT FROM AUTHOR]

Microstructural engineering in conjunction with compositional design has been used for tailoring the properties of piezoelectric materials. In piezoelectric ceramics, the plate-like particles are used for the seed materials in order to realize the textured microstructures. In this study, the seed crystals are synthesized by simple molten salt synthesis (SMSS), using a generalized rule for driving the abnormal grain growth in (K,Na)NbO 3 (KNN)-based ceramics. Furthermore, the textured ceramics are successfully produced in Ba-doped KNN materials, using the seed crystals which are grown by SMSS. Consequently, the textured ceramic shows the Lotgering factor of 92% and the piezoelectric constant (d 33) which is similar to that of a single crystal. It is suggested that the excess donor ratio must be considered to obtain the seed crystals (synthesized by SMSS) and textured microstructures in KNN-based ceramics. [ABSTRACT FROM AUTHOR]

ZnS nanopowders annealed at low temperatures (≤550 °C) have a pure cubic structure, while a small amount of hexagonal phase formed in specimens annealed at temperatures ≥700 °C. The particle sizes of the ZnS nanopowders increased with the annealing temperature. ZnS ceramics that were sintered using ZnS nanopowders annealed at low temperatures (≤550 °C) exhibited low transmittance, because of their porous microstructure. ZnS ceramics that were synthesized using ZnS powders annealed at high temperatures (≥800 °C) containing large agglomerated particles, also exhibited low transmittance, due to the presence of a liquid phase. A carbonate absorption band was found from the ZnS ceramics with small grains, because carbon ions diffused from the graphite mold into the ZnS ceramics during sintering, probably through the grain boundaries, and formed carbonates. A ZnS ceramic that was sintered at 1020 °C using the nanopowders annealed at 750 °C exhibited dense microstructure, with a large transmittance, 68%, in the wavelength range 6.0–12 μm. [ABSTRACT FROM AUTHOR]

Abstract: Nano-sized SiO x is synthesized by an evaporation and condensation process using induction melting with the injection of various mixed gases. In particular, the effects of O2 gas on their microstructures and electrochemical properties are investigated. The x-values of the synthesized SiO x can be controlled from 1.18 to 1.83 by varying the O2/Ar ratios in the injected gas. A micro-structural analysis reveals that mixture of nanoparticles and nanowires is formed and that the relative amount of nanowire decreases with an increase of the oxygen contents in the injected gas. When x is low, crystalline Si is formed, but this phase disappears when x exceeds 1.28. From the electrochemical analysis of the various SiO x powders, the Initial Columbic Efficiency (ICE) decreases with the increase in the x-values – largely due to the oxidation of Li-ions such as Li2O and Li4SiO4. Cycle stability, however, is improved with the increase of the x-values, indicating that strain and stress during insertion and extraction of Li-ions are properly released due to the oxide buffer around the Si as well as the nano-sized structure. When x = 1.18, a specific capacity of 660 mAh g−1 with a columbic efficiency of 99.8% at the 50th cycle is obtained. [Copyright &y& Elsevier]

The structural and piezoelectric properties of the x mol% MnO2-added 0.95(Na0.5−x/200K0.5−x/200)NbO3–0.05SrTiO3 [(NK)xMN-ST] ceramics were investigated. A dense microstructure with enlarged grains was formed for the specimens sintered at 1040°C through liquid-phase sintering. However, the grain size decreased for the specimen sintered at 1060°C because of the formation of a large amount of the liquid phase. Therefore, the microstructural variations in the (NK)xMN-ST ceramics can be explained by liquid-phase-assisted abnormal grain growth. The specimens sintered at 1020 and 1060°C showed low piezoelectric properties because of their low relative density and small grain size, respectively. On the other hand, the (NK)xMN-ST ceramic with x =0.1 sintered at 1040°C showed promising piezoelectric properties: d 33 =260pC/N, k p =0.42, Q m =202 and . [ABSTRACT FROM AUTHOR]

Abstract: Bi12SiO20 ceramics were well sintered at 800°C after calcination at 700°C. A liquid phase of composition Bi2O3 was formed during the sintering at temperatures ≥800°C and assisted the densification of the Bi12SiO20 ceramics. When the sintering temperature exceeded 800°C, however, the relative density, ɛ r, and Q × f values of the Bi12SiO20 ceramics decreased, probably due to the formation of a large amount of the liquid phase. The Bi12SiO20 ceramics sintered at 800°C for 5.0h exhibited excellent microwave dielectric properties with a high ɛ r of 43, a high Q × f of 86,802GHz and a small τ f of −10.39ppm/°C. [Copyright &y& Elsevier]

Abstract: ZnO was used to decrease the sintering temperature of 1.5mol% MnO 2 -added (Na0.5K0.5)NbO3(MNKN) ceramics. When a small amount of ZnO (≥2.0mol%) was added, a dense microstructure was observed for specimens sintered at 960°C, with high relative density of 96.0% of the theoretical density. The liquid phase, which was considered to be an Nb2O5–MnO–ZnO related phase, was formed in the ZnO-added MNKN ceramics and abnormal grain growth occurred in its presence. Therefore, although a very small amount of ZnO might enter the matrix of the MNKN, most of the ZnO was used to form the liquid phase and assisted the densification of the specimens, indicating that the hardening effect of Zn2+ was insignificant. The 2.0mol% ZnO-added MNKN (ZMNKN) ceramics sintered at 960°C exhibited the high piezoelectric properties of k p =37%, , d 33 =120pC/N, and Q m =200. In addition, the reaction between the Ag electrode and the ZMNKN ceramic sintered at 960°C was negligible. [Copyright &y& Elsevier]

Abstract: [(Na0.5K0.5)1−x Li x ](Nb0.96Sb0.04)O3 [NKLNS100x] ceramics with 0.0 ≤ x ≤ 0.1 were sintered at 1040 °C for 2 h and the specimens with x ≥ 0.05 had a dense microstructure due to liquid phase sintering. The specimen with x = 0.05 had both orthorhombic and tetragonal phases, and showed good piezoelectric properties of k p = 0.43, d 33 = 243 pC/N and ɛ33 T /ɛ 0 = 990. The [(Na0.5K0.5)0.95Li0.05](Nb0.96Sb0.04)O3 [NKLNS5] ceramics sintered at 960 °C also showed a high density by the addition of CuO, due to the production of the CuO and Na2O-related liquid phase. The Cu2+ ions were considered to replace Nb5+ ions and act as a hardener, which increased the Q m value of the NKLNS5 ceramics. High piezoelectric properties of k p = 0.37, Q m = 560, ɛ 33 T /ɛ 0 = 600 and d 33 = 170 pC/N were obtained from the specimen containing 1.5 mol% of CuO sintered at 960 °C for 2 h. [Copyright &y& Elsevier]

Abstract: The sintering temperature of 0.75Pb(Zr0.47Ti0.53)O3–0.25Pb(Zn1/3Nb2/3)O3 ceramics containing 1.5mol% MnO2 was decreased from 930 to 850°C with the addition of CuO. The CuO reacted with the PbO and formed a liquid phase during the sintering, which assisted the densification of the specimens. Most of the Cu2+ ions existed in the CuO second phase, thereby preventing any possible hardening effect from the Cu2+ ions. Variations of the k p, Q m, ɛ 3 T/ɛ 0 and d 33 values with CuO were similar to that of the relative density. The specimen containing 0.5mol% CuO sintered at 850°C showed the good piezoelectric properties of k p =0.5, Q m =1000, ɛ 3 T/ɛ 0 =1750 and d 33 =300pC/N. [Copyright &y& Elsevier]

Abstract: The addition of a small amount of CuO to the 0.95(Na0.5K0.5)NbO3–0.05CaTiO3 (0.95NKN–0.05CT) ceramics sintered at 960°C for 10h produced a dense microstructure with large grains due to the liquid phase sintering. Due to the negligible Na2O evaporation, poling was easy for all specimens sintered at 960°C. The piezoelectric properties of the specimens were considerably influenced by the relative density, grain size and liquid phase amount. The high piezoelectric properties of d 33 =200pC/N, k p =0.37, and Q m =350 were obtained for the 0.95NKN–0.05CT ceramics containing 2.0mol% CuO sintered at 960°C for 10h. Therefore, the 0.95NKN–0.05CT ceramics containing a small amount of CuO are a good candidate material for lead-free piezoelectric ceramics. [Copyright &y& Elsevier]

Abstract: BaSm2Ti4O12 (BST) film grown at room temperature was amorphous, while the film grown at 300°C was also amorphous but contained a small amount of crystalline Sm2Ti2O7 (ST). The crystalline BST phase was formed when the film was grown at 700°C and subjected to rapid thermal annealing (RTA) at 900°C. On the other hand, the ST phase was formed in the film grown at 300°C and subjected to RTA at 900°C. A high capacitance density of 2.12fF/μm2 and a low leakage current density of 1.15fA/pFV were obtained from the 150nm-thick BST film grown at 300°C. Its capacitance density could conceivably be further increased by decreasing the thickness of the film. It had linear and quadratic coefficients of capacitance of −785ppm/V and 5.8ppm/V2 at 100kHz, respectively. Its temperature coefficient of capacitance was also low, being approximately 255ppm/°C at 100kHz. [Copyright &y& Elsevier]

Abstract: BaTi4O9 thin films have been prepared by RF magnetron sputtering on the Pt/Ti/SiO2/Si substrates and the dielectric properties of the BaTi4O9 film have been investigated at microwave frequency range. The homogeneous BaTi4O9 thin film was obtained when the film was grown at 550°C and rapid thermal annealed (RTA) at 900°C for 3min. The circular-patch capacitor (CPC) was used to measure the microwave dielectric properties of the film. The dielectric constant (ɛ r) and the dielectric loss (tan δ) were successfully measured up to 6GHz. The ɛ r of the BaTi4O9 thin film slightly increased with the increase of the film thickness. However, the tan δ decreased with increasing the thickness of the film. The ɛ r of BaTi4O9 thin film was similar to that of the BaTi4O9 ceramics, which is about 36–39. The tan δ of the film with 460nm thickness was very low approximately, 0.0001 at 1–3GHz. Since BaTi4O9 film has a high ɛ r and a low tan δ, the BaTi4O9 film can be used as the microwave devices. [Copyright &y& Elsevier]

Abstract: BaTi5O11 thin films were grown on the poly-Si/SiO2/Si substrate using rf magnetron sputtering. The BaO-TiO2 thin film deposited on the poly-Si substrate had an amorphous phase even though the growth temperature was high at 550°C. The amorphous film was crystallized into the BaTi5O11 phase when the film was post annealed above 800°C. The post annealing temperature is one of the most important factors for the formation of the crystalline BaTi5O11 thin film. The homogeneous BaTi5O11 thin film was obtained when the film was grown at 550°C and rapid thermal annealed (RTA) at 900°C for 3min. The dielectric constant (ɛ r) of the BaTi5O11 film measured at 100kHz was about 35 and the dissipation factors of all the films were smaller than 4.0%. The dielectric properties of the BaTi5O11 thin film were also measured at microwave frequencies. For the BaTi5O11 thin film grown at 550°C and RTA at 900°C for 3min, the ɛ r of 34–30 and dielectric loss of 0.025±0.005 were obtained at 1–6GHz. [Copyright &y& Elsevier]

Abstract: Ti-rich BaO–TiO2 thin films were grown on a Pt/Ti/SiO2/Si substrate using rf sputtering and the structural and dielectric properties of the films were investigated. For the film grown at room temperature and rapidly thermal annealed (RTA) at 900°C for 3min, an amorphous phase with a small BaTi5O13 crystalline phase was formed. As the growth temperature increased, the amount of the BaTi5O11 crystalline phase increased. For the film grown at 350°C and RTA at 900°C for 3min, the homogeneous BaTi5O11 phase was formed. The BaTi4O9 phase was developed when the growth temperature exceeded 450°C. The thin film with the homogeneous BaTi4O9 phase was obtained when the film was grown at 550°C and RTA at 900°C for 3min. The dielectric properties of the films were measured at 1–6GHz range. The dielectric constant (ϵ r) of the BaTi5O11 film was about 33 and the dissipation factor was about 0.01. The ϵ r and the dissipation factor of the BaTi4O9 film were about 37 and 0.005, respectively. [Copyright &y& Elsevier]