Pharatree Jaita

Investigation of a new lead-free Bi0.5(Na0.40K0.10)TiO3-(Ba0.7Sr0.3)TiO3 piezoelectric ceramic.

Lead-free piezoelectric compositions of the (1-x)Bi0.5(Na0.40K0.10)TiO3-x(Ba0.7Sr0.3)TiO3 system (when x = 0, 0.05, 0.10, 0.15, and 0.20) were fabricated using a solid-state mixed oxide method and sintered between 1,050°C and 1,175°C for 2 h. The effect of (Ba0.7Sr0.3)TiO3 [BST] content on phase, microstructure, and electrical properties was investigated. The optimum sintering temperature was 1,125°C at which all compositions had densities of at least 98% of their theoretical values. X-ray diffraction patterns that showed tetragonality were increased with the increasing BST. Scanning electron micrographs showed a slight reduction of grain size when BST was added. The addition of BST was also found to improve the dielectric and piezoelectric properties of the BNKT ceramic. A large room-temperature dielectric constant, εr(1,609), and piezoelectric coefficient, d33 (214 pC/N), were obtained at an optimal composition of x = 0.10.

Effect of composition on electrical properties of lead-free Bi0.5(Na0.80K0.20)0.5TiO3-(Ba0.98Nd0.02)TiO3 piezoelectric ceramics

Lead-free piezoelectric ceramics with the composition of (1−x)Bi0.5(Na0.80K0.20)0.5TiO3-x(Ba0.98Nd0.02)TiO3 or (1−x) BNKT-xBNdT (with x = 0–0.20 mol fraction) have been synthesized by a conventional mixed-oxide method. The compositional dependence of phase structure and electrical properties of the ceramics were systemically studied. The optimum sintering temperature of all BNKT-BNdT ceramics was found to be 1125 °C. X-ray diffraction pattern suggested that BNdT effectively diffused into BNKT lattice during sintering to form a solid solution with a perovskite structure. Scanning electron micrographs showed a slight reduction of grain size when BNdT was added. It was found that BNKT-0.10BNdT ceramic exhibited optimum electrical properties (er = 1716, tanδ = 0.0701, Tc = 327 °C, and d33 = 211 pC/N), suggesting that this composition has a potential to be one of a promising lead-free piezoelectric candidate for dielectric and piezoelectric applications.

Compositional Range and Electrical Properties of Lead-Free Bi0.5(Na0.8K0.2)0.5TiO3-(Ba0.98Nd0.02) TiO3 System

Lead-free piezoelectric ceramics (1−x)Bi0.5(Na0.8K0.2)0.5TiO3-x(Ba0.98Nd0.02)TiO3 or (1−x)BNKT-xBNdT (x = 0.05–0.15 mol fraction) were synthesized by conventional mixed-oxide method. All samples had relative densities more than 98% of theoretical values. All compositions had pure perovskite structure and BNdT effectively diffused into BNKT lattice during sintering to form solid solutions. Grain size and shape were slightly affected by BNdT addition. The addition of BNdT into BNKT was also found to affect dielectric, ferroelectric and piezoelectric performances with the maximum values (Tm = 328°C, ϵr = 1736, tanδ = 0.0714, Pr = 21.91 μC/cm2, d33 = 228 pC/N) observed in 0.89BNKT-0.11BNdT composition.

Composition range and electrical properties of the morphotropic phase boundary in Bi0.5(Na0.80K0.20)0.5TiO3-(Ba0.7Sr0.3)TiO3 system

The lead-free piezoelectric ceramic binary system of (1-x)Bi0.5(Na0.80K0.20)0.5TiO3-x(Ba0.7Sr0.3)TiO3 or (1-x) BNKT-xBST (with x ranging from 0.05 to 0.15 mol fraction) near the morphotropic phase boundary (MPB) has been investigated. The ceramics were synthesized by a conventional mixed-oxide method and sintered at 1125°C for 2 h. All BNKT-BST samples had relative density higher than 98% of their theoretical values. X-ray diffraction patterns showed that all compositions had a pure perovskite structure and BST effectively diffused into the BNKT lattice during sintering to form a solid solution. Crystal structure changed from rhombohedral-rich phase to tetragonal-rich phase with increasing BST content. Because of such MPB-like behavior, the highest dielectric (Tc = 325°C, ɛr = 1827, tan δ = 0.0823) and piezoelectric performances (d33 = 225 pC/N) were obtained in the BNKT-0.11BST sample.

Large electric field-induced strain and piezoelectric responses of lead-free Bi0.5(Na0.80K0.20)0.5TiO3-Ba(Ti0.90Sn0.10)O3 ceramics near morphotropic phase boundary

Lead-free piezoelectric ceramics with compositions belonging to family of compositions (1−x)Bi0.5(Na0.80K0.20)0.5TiO3-xBa(Ti0.90Sn0.10)O3 or (1−x) BNKT-xBTS (when x = 0.05 − 0.15 mol fraction) near the morphotropic phase boundary (MPB) were fabricated by a conventional mixed oxide method. Sintered samples had relative densities greater than 98% of their theoretical values. X-ray diffraction data revealed that the MPB region consisted of coexisting rhombohedral and tetragonal phases in the BNKT-BTS system was identified over the entire compositional range. A large electric field-induced strain (Smax) of 0.36% and a normalized strain coefficient (d*33) of 649 pm/V were observed in the BNKT-0.05BTS sample. The sample close to the MPB composition (BNKT-0.11BTS) exhibited the maximum dielectric constant (εr = 1770), temperature of maximum permittivity (Tm = 333C°) and low-field piezoelectric coefficient (d33 = 227 pC/N), along with reasonable ferroelectric properties (Pr = 20.6 mC/cm2, Rsq = 0.88) and strain properties (d*33 = 445 pm/V and Smax = 0.24%).

Electrical properties of ternary system Bi0.5(Na0.80K0.20)0.5TiO3-0.005LiNbO3-BaTiO3 lead-free piezoelectric ceramics

ABSTRACT Ternary system of lead-free piezoelectric ceramics with the formula of (1-x-y)Bi0.5(Na0.80K0.20)0.5TiO3-xLiNbO3-yBaTiO3 or (1-x-y)BNKT-xLN-yBT (x = 0.005 and y = 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06 and 0.07 mol fraction) were sintered at the temperature of 1125°C for 2 h. All samples have the density ranging of 5.59 - 5.73 g/cm3. X-ray diffraction pattern exhibited a single perovskite structure without any secondary phase. Scanning electron micrographs indicated a cubic-like grain shape occurred for all compositions with side length of 0.49 - 0.77 μm. At a composition BNKT-0.005LN-0.04BT showed the highest piezoelectric coefficient (d33 = 198 pC/N) with good dielectric (ϵr = 1775, tanδ = 0.0534) and ferroelectric properties (Pr = 17.36 μC/cm2, Rsq = 1.67).

Enhanced magnetic performance of lead-free (Bi 0.5 Na 0.5 )TiO 3 -CoFe 2 O 4 magnetoelectric ceramics

This research was conducted to study the magnetoelectric ceramics with the composition belonging to (1-x)(Bi0.5Na0.5)TiO3-xCoFe2O4 or (1-x)BNT-xCF (when x = 0 - 0.02 mol fraction). All compositions have been synthesized by a conventional mixed oxide method and sintered at the temperature ranging of 900°C–1150°C. The ceramics were fabricated to investigate the effects of CF on crystal structure, microstructure, magnetoelectric effect (ME) and electrical properties of BNT ceramic. The optimum sintering temperature was found to be 1100°C for pure BNT ceramic and 1000°C for BNT-CF sample group. X-ray diffraction pattern revealed that all compositions exhibited a single perovskite structure without impurity phase. Diffraction peaks from the amount of CF were not observed in these patterns which may be due to the relatively low concentration of CF added into BNT ceramic and may be below the detection limit of the instrument. The reduction of grain size and dielectric improvement were observed when CF was added. The addition of CF improved the magnetic behavior as well as resulted in a slight change in ferroelectric properties. The addition of 2 mol. % CF into BNT was found to be the optimal composition for produce the magnetoelectric materials simultaneously exhibiting good ferromagnetic and ferroelectric properties at room temperature.

Characterization of Metakaolin-Based Materials for Dye Adsorption from Aqueous Solution

The properties of metakaolin-based materials were investigated. The studied materials were prepared by mixing metakaolin and aluminum oxide in alkaline solution. The obtained samples were cast into plastic molds and then left at 27°C for 24 h. The properties of the materials were investigated using XRD, FTIR, and SEM. The obtained results suggested that reaction of the mixed materials occurred. The adsorption properties of the materials, including removal efficiency, distribution coefficient, and uptake capacity were determined. The obtained results revealed that the studied materials exhibited high adsorption capacity, which is good for the adsorbent applications.

Effects of Sintering Temperatures on Structural, Electrical and Mechanical Properties of BNKT Piezoelectric Ceramics

This research investigated the effects of sintering temperatures on the structural, dielectric, ferroelectric, piezoelectric and mechanical properties of lead-free Bismuth Sodium Potassium Titanate (BNKT) piezoelectric ceramics. The BNKT ceramics were prepared by solid-state mixed oxide method and sintering at temperature ranging from 1100 to 1150°C for 2 h. All ceramics sample showed highly density and reach a maximum at sintering temperature 1125°C of 5.81 g/cm3. X-ray diffraction patterns exhibited pure perovskite structure with coexisting of rhombohedral-tetragonal phases for all compositions. The microstructure was characterized by Scanning Electron Microscope (SEM), from SEM image the ceramics showed cubic-like grain shape. The average grain size increased with increasing sintering temperature. The dielectric permittivity showed the optimum sintering at 1125°C with reach a maximum dielectric constant of 4,194. Furthermore, at sintering temperature 1125°C present highest strain (Smax = 0.14%) with a large normalized strain coefficient (d*33 = Smax/Emax) of 233 pm/V.

Processing and Properties of Biphasic Calcium Phosphates Bioceramics Derived from Biowaste Materials

Properties of biphasic calcium phosphates bioceramics derived from biowaste materials were investigated. The hydroxyapatite (HA) powder was synthesized from bovine bone via thermal treatment while β-tricalcium phosphate (β-TCP) powder was synthesized from mussel shells via solid state solution. Pure HA and β-TCP were successful obtained. The HA and β-TCP were mixed together and sintered at 1100 - 1350°C. The effects of the sintering temperature and the ratio of HA/ β-TCP on the properties of the studied samples were investigated. The sintering temperature at 1250°C presented the maximum value of density and hardness. X-ray analysis of BCP ceramics sintered at 1250°C presented multiple phases of calcium phosphate. Average grain sizes of the studied samples decreased as the ratio of HA increased.