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Fine powders of bismuth potassium titanate (Bi1/2K1/2)TiO3 (BKT) synthesized by hydrothermal reactions have been reported to have good sinterability and high chemical stability against long-time sintering. In this study, detailed chemical and structural characterizations were performed on a hydrothermal BKT powder sample to identify the origin of such properties. The results of X-ray diffraction, infrared transmittance, and diffuse reflectance measurements revealed that the hydrothermal BKT particle contained high concentrations of lattice hydroxyl group and Bi vacancy, whereas the observation by transmission electron microscope showed that its surface was covered with numerous Bi2O3 nanoparticles to achieve the overall stoichiometric cation ratio of BKT. We found that the unique composite nanostructure of the hydrothermal BKT powder led to a large suppression of Bi evaporation during high-temperature sintering, thereby contributing to its superior chemical stability.

Fine powders of bismuth potassium titanate (Bi1/2K1/2)TiO3 (BKT) synthesized by hydrothermal reactions have been reported to have good sinterability and high chemical stability against long-time sintering. In this study, detailed chemical and structural characterizations were performed on a hydrothermal BKT powder sample to identify the origin of such properties. The results of X-ray diffraction, infrared transmittance, and diffuse reflectance measurements revealed that the hydrothermal BKT particle contained high concentrations of lattice hydroxyl group and Bi vacancy, whereas the observation by transmission electron microscope showed that its surface was covered with numerous Bi2O3 nanoparticles to achieve the overall stoichiometric cation ratio of BKT. We found that the unique composite nanostructure of the hydrothermal BKT powder led to a large suppression of Bi evaporation during high-temperature sintering, thereby contributing to its superior chemical stability. [ABSTRACT FROM AUTHOR]

Bismuth potassium titanate, (Bi1/2K1/2)TiO3 (BKT), ceramics were fabricated using smaller-particle-size TiO2 (~0.1 μm) as a starting material for the improvement of BKT ceramic densiflcation. The BKT ceramics were prepared by a conventional ceramic fabrication process without any additives or special techniques, such as hot-pressing methods. The BKT ceramics prepared using TiO2 (~0.1 μm) powder had high density ratios of at least 95%. In addition, they had good electrical properties equal to or greater than the BKT ceramics prepared by other manufacturing methods. [ABSTRACT FROM AUTHOR]

Bismuth potassium titanate, (Bi1/2K1/2)TiO3(BKT), ceramics were fabricated using smaller-particle-size TiO2(∼0.1 μm) as a starting material for the improvement of BKT ceramic densification. The BKT ceramics were prepared by a conventional ceramic fabrication process without any additives or special techniques, such as hot-pressing methods. The BKT ceramics prepared using TiO2(∼0.1 μm) powder had high density ratios of at least 95%. In addition, they had good electrical properties equal to or greater than the BKT ceramics prepared by other manufacturing methods. [ABSTRACT FROM PUBLISHER]

The effect of sintering temperature (975–1025°C) on crystal structure, microstructure and dielectric properties of perovskite bismuth potassium titanate (BKT) ceramics was investigated. The pure BKT ceramics were firstly prepared using the combustion technique. The phase purity, crystal structure and microstructure of samples were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The purity phase of BKT samples, which has a tetragonal structure, was observed in all samples. The lattice parameters a, c and the tetragonality tended to decrease with increased sintering temperature. The SEM result showed the average grain size increased (0.37–0.58 μm) with the increase of sintering temperature (975–1025°C). The shrinkage of the ceramics increased when the sintering temperature increased. The maximum density and dielectric constant at Curie temperature were around 5.71 g/cm3and 3850, and were obtained from the sample sintered at 1020°C for 2 h. Importantly, the preparation using the combustion technique can improve the density and dielectric properties of BKT ceramics. [ABSTRACT FROM PUBLISHER]

Bismuth potassium titanate [(Bi0.5K0.5)TiO3; BKT] ceramics were fabricated by the solid state reaction method using calcination and sintering temperatures of 800°C and 1030°C. To prevent Bi2O3and K2CO3evaporation during the firing process, excess Bi2O3and K2CO3in the ratio of 1:1 were added to the samples in varying amounts from 0–10 mol%. The XRD results of all samples were indexed in a tetragonal structure. The lattice parametersa,cand thec/aratio tended to decrease with increasing excess Bi2O3and K2CO3. The average particle size increased while the average grain size decreased with increasing amounts of Bi2O3and K2CO3. The porous microstructure slightly decreased with an increasing amount of Bi2O3and K2CO3, up to 1 wt.%, and then slightly increased with higher amount of excess Bi2O3and K2CO3. The density (ρ = 5.75 g/cm3), dielectric constant (ϵr= 5,584) and dielectric loss (tanδ = 0.76) can be improved by adding 1 wt.% of excess Bi2O3and K2CO3. [ABSTRACT FROM PUBLISHER]

Dense and phase-pure ferroelectric ceramics of 75 mol.% Bi0.5K0.5TiO3– 25 mol.% BiFeO3are prepared by the conventional solid state reaction method. Their crystal structure is analyzed and discussed. The dielectric and piezoelectric properties of the ceramics are investigated at various temperatures. The ceramics exhibit relaxor-like dielectric properties and high electric field-induced strain (equivalent to 250-300 pm/V at 25-75°C), not previously reported for this composition, making it a promising lead-free alternative for actuator applications. [ABSTRACT FROM AUTHOR]

Abstract: Lead-free x Bi0.5Na0.5TiO3–y BaTiO3–z Bi0.5K0.5TiO3 piezoelectric ceramics were synthesized by a conventional solid state reaction method. The microstructure, ferroelectric and piezoelectric properties of the ceramics were investigated. Structure measurements by X-ray diffraction with Rietveld refinement have allowed us to specify more precisely the morphotropic phase boundary (MPB) in this system. For (1− x) BNT–x BT solid solution ceramics, the 0.94 BNT–0.06 BT morphotropic composition shows the higher values with d 33 =170pC/N, k p =0.35 and k t =0.53. In the case of (1− x) BNT–x BKT compositions, the d 33, k p and k t are, respectively, 137pC/N, 0.39 and 0.54 for the 0.80 BNT–0.20 BKT ceramic. On the other hand, the ternary 0.865 BNT–0.035 BT–0.100 BKT morphotropic composition shows high piezoelectric constant and electromechanical coupling factors (d 33 =133pC/N, k p =0.26 and k t =0.57). [Copyright &y& Elsevier]

Dielectric and piezoelectric properties of lead-free (1-x)(Bi0.5K0.5)TiO3-xBiFeO3 ceramics prepared by a conventional solid-state reaction method were studied in the range of x = 0∼40 mol%. A tetragonal perovskite structure was maintained at x = 0∼10 mol% forming a solid solution between (Bi0.5K0.5)TiO3 and BiFeO3 with no secondary phase. Piezoelectric coefficient (d33) increased from 31 pC/N at x = 0 mol% to 64 pC/N at x = 6 mol% and then decreased with further addition of x. Depolarization temperature (Td) gradually decreased with increasing x from 302°C at x = 0 mol% to 163°C at x = 20 mol% and slightly increased up 180°C at x = 40 mol%. [ABSTRACT FROM AUTHOR]

Control of the microstructures of (1-x)(Bi1/2K1/2)TiO3-xBaTiO3 (x = 0.1) [abbreviated as BKT-BT10] ceramics prepared by a reactive templated grain growth (RTGG) using platelike Bi4Ti3O12 particles as a template were investigated. All samples showed a single-phase perovskite structure. The degree of orientation F, which was determined by the Lotgering method using X-ray diffraction pattern, achieved only ∼ 60% in textured BKT-BT10 ceramics. Textured BKT-BT10 ceramics with a homogeneous microstructure were obtained by the the longer sintering time. It is very important to perform long sintering in order to promote the grain growth and improve the orientation factor for this composition. [ABSTRACT FROM AUTHOR]

The structural, dielectric, ferroelectric and piezoelectric properties of 0.90[x(Bi1/2 Na1/2)TiO3-(1-x)(Bi1/2K1/2)TiO3]-0.10(Bi1/2Ag1/2)TiO3 (BNKA) ceramics were studied for the compositional range, x = 0.73-0.89. The morphotropic phase boundary (MPB) composition of the system appears to be near BNKA-79 according to the results of the X-ray diffraction. The optimal piezoelectric properties are observed in the MPB region. The sample with x = 0.79 showed the highest piezoelectric constant d33 = 160 pC/N. The maximum electromechanical coupling factors, kp and kt, are 0.30 for BNKA-79 and 0.42 for BNKA-85, respectively. [ABSTRACT FROM AUTHOR]

The piezoelectric properties of a solid solution, x(Bi1/2Na1/2)TiO3-(1-x)(Bi1/2K1/2) TiO3 + La2O3 y wt% [BNKTx + La2O3 y wt%; x = 0.50, 0.70, y = 0-0.6] were investigated, focusing on piezoelectric constant, d33, and depolarization temperature, Td. The dielectric constant increased with increasing La2O3 content (y). The highest electromechanical coupling factor, k33 (0.493) and the highest d33 (153 pC/N) was obtained in BNKT0.70 + La2O3 0.2wt%. The Td of BNKT0.70 + La2O3 y wt% was almost the same with y = 0-0.3 at 210-220°C and decreased with y ≥ q 0.4. BNKT0.70 + La2O3 0.2 wt% (d33 = 153 pC/N and Td = 219°C) is a good candidate for practical use in actuators. [ABSTRACT FROM AUTHOR]

Potassium bismuth titanate nanoparticles were prepared by the hydrothermal method using Ti(C4H9O)4 and Bi(NO3)3·5H2O as raw materials in alkaline solution at temperatures of 160–200°C. The crystal phase, particle size, morphology and dispersion of the particles were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the particles with sizes of about 50–100 nm in diameter are well-dispersed K0.5Bi0.5TiO3 (KBT) crystals of tetragonal structure, and the alkaline concentration and the temperature of solutions have great effects on the phase composition and morphology of the resultant particles. We could gain the KBT phase of high purity when the concentration of KOH is about 8–12 M and the reaction temperature is about 170–180°C. [ABSTRACT FROM AUTHOR]