Comparison of ultrasound-assisted extraction with conventional extraction methods of oil and polyphenols from grape (Vitis vinifera L.) seeds

Ultrasound-assisted extraction (US) carried out at 20 KHz, 150 W for 30 min gave grape seed oil yield (14% w/w) similar to Soxhlet extraction (S) for 6 h. No significant differences for the major fatty acids was observed in oils extracted by S and US at 150 W. Instead, K₂₃₂ and K₂₆₈ of US- oils resulted lower than S-oil. From grape seeds differently defatted (S and US), polyphenols and their fractions were extracted by maceration for 12 h and by ultrasound-assisted extraction for 15 min. Sonication time was optimized after kinetics study on polyphenols extraction. Grape seed extracts obtained from seeds defatted by ultrasound (US) and then extracted by maceration resulted the highest in polyphenol concentration (105.20 mg GAE/g flour) and antioxidant activity (109 Eq αToc/g flour).     

Band diagram for chemical vapor deposition diamond surface conductive layer: Presence of downward band bending due to shallow acceptors

The properties of surface conductivity (SC) of impurity-non-doped CVD diamond (001) samples were studied by various methods of sheet-resistance (R_S) measurement, Hall-effect measurement, XPS, UPS, SES, SR-PES, PEEM and 1D band simulation taking into account special emphases on deriving the information about the surface band diagram (SBD). The R_S values in UHV conditions were determined after no-annealing or 200 ～ 300 °C annealing in UHV. C 1 s XPS profiles were measured in detail in bulk-sensitive and surface-sensitive modes of photoelectron detection. The energy positions of valence band top (E_V) relative to the Fermi level (E_F) in UHV conditions after no-annealing or 200 ～ 300 °C annealing in UHV were determined. One of the samples was subjected to SR-PES, PEEM measurements. The SBDs were simulated by a band simulator from the determined R_S and E_V ? E_F values for three samples based on the two models of surface conductivity, namely, so-called surface transfer doping (STD) model and downward band bending with shallow acceptor (DBB/SA) model. For the DBB/SA model, there appeared downward bends of SBDs toward the surface at a depth range of ～ 1 nm. C 1 s XPS profiles were then simulated from the simulated SBDs. Comparison of simulated C 1 s XPS profiles to the experimental ones showed that DBB/SA model reproduces the C 1 s XPS profiles properly. PEEM observation of a sample can be explained by the SBD based on the DBB/SA model. Mechanism of SC of CVD diamonds is discussed on the basis of these findings. It is suggested that the STD model combined with SBD of DBB/SA model explains the surface conductivity change due to environmental changes in actual cases of CVD diamond SC with the presence of surface E_F controlling defects.     

Ultrasound-assisted extraction and purification of schisandrin B from Schisandra chinensis (Turcz.) Baill seeds: Optimization by response surface methodology

The objective of this study is to develop a process consisting of ultrasonic-assisted extraction, silica-gel column chromatography and crystallization to optimize pilot scale recovery of schisandrin B (SAB) from Schisandra chinensis seeds. The effects of five independent variables including liquid–solid ratio, ethanol concentration, ultrasonic power, extraction time, and temperature on the SAB yield were evaluated with fractional factorial design (FFD). The FFD results showed that the ethanol concentration was the only significant factor for the yield of SAB. Then, with the liquid–solid ratio 5 (mL/g) and ultrasonic power 600 W, the other three parameters were further optimized by means of response surface methodology (RSM). The RSM results revealed that the optimal conditions consisted of 95% ethanol, 60 °C and 70 min. The average experimental SAB yield under the optimum conditions was found to be 5.80 mg/g, which was consistent with the predicted value of 5.83 mg/g. Subsequently, a silica gel chromatographic process was used to prepare the SAB-enriched extract with petroleum ether/acetone (95:5, v/v) as eluents. After final crystallization, 1.46 g of SAB with the purity of 99.4% and the overall recovery of 57.1% was obtained from 400 g seeds powder. This method provides an efficient and low-cost way for SAB purification for pharmaceutical industrial applications.     

Purification of serratiopeptidase from Serratia marcescens NRRL B 23112 using ultrasound assisted three phase partitioning

The ultrasound assisted three phase partitioning (UATPP) is a novel bioseparation method for separation and purification of biomolecules. In the present work, UATPP was investigated for the first time for purification of serratiopeptidase from Serratia marcescens NRRL B 23112. Effect of various process parameters such as ammonium sulphate saturation, t-butanol to crude extract ratio, pH, ultrasonic frequency, ultrasonic intensity, duty cycle and irradiation time were evaluated and optimized. The optimized conditions were found to be as follows: ammonium sulphate saturation 30% (w/v), pH 7.0, t-butanol to crude ratio 1:1 (v/v), ultrasound frequency 25 kHz, ultrasound intensity 0.05 W/cm², duty cycle 20% and irradiation time 5 min. The maximum purity and recovery obtained from UATPP was 9.4-fold and 96% respectively as compared to the three phase partitioning (TPP) (4.2-fold and 83%). Also the process time for UATPP was significantly reduced to 5 min from 1 h as compared to TPP. The results indicate that, UATPP is an efficient technique for the purification of serratiopeptidase with maximum purity, recovery and reduced processing time.     

Optimization of ultrasound-assisted extraction of bioactive compounds from wild garlic (Allium ursinum L.)

Ultrasound-assisted extraction was used for extraction of bioactive compounds and for production of Allium ursinum liquid extract. The experiments were carried out according to tree level, four variables, face-centered cubic experimental design (FDC) combined with response surface methodology (RSM). Temperature (from 40 to 80 °C), ethanol concentration (from 30% to 70%), extraction time (from 40 to 80 min) and ultrasonic power (from 19.2 to 38.4 W/L) were investigated as independent variables in order to obtain the optimal conditions for extraction and to maximize the yield of total phenols (TP), flavonoids (TF) and antioxidant activity of obtained extracts. Experimental results were fitted to the second order polynomial model where multiple regression and analysis of variance were used to determine the fitness of the model and optimal condition for investigated responses. The predicted values of the TP (1.60 g GAE/100 g DW), TF (0.35 g CE/100 g DW), antioxidant activity, IC₅₀ (0.71 mg/ml) and EY (38.1%) were determined at the optimal conditions for ultrasound assisted extraction: 80 °C temperature, 70% ethanol, 79.8 min and 20.06 W/L ultrasonic power. The predicted results matched well with the experimental results obtained using optimal extraction conditions which validated the RSM model with a good correlation.     

Effects of various factors of ultrasonic treatment on the extraction recovery of drugs from fish tissues

In the present research, a combined extraction method of ultrasound-assisted extraction (UAE) in conjunction with solid phase extraction (SPE) was applied to isolation and enrichment of selected drugs (metoprolol, ticlopidine, propranolol, carbamazepine, naproxen, acenocumarol, diclofenac, ibuprofen) from fish tissues. The extracted analytes were separated and determined by ultra-high performance liquid chromatography with UV detection (UHPLC–UV) technique. The selectivity of the developed UHPLC–UV method was confirmed by comparison with ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) analysis.The important parameters, such as composition of type and pH of extraction solvent, solid/liquid rate volume of extraction solvent and number of extraction cycles were studied. The ultrasonic parameters, such as time, power and temperature of the process were optimized by using a half-fraction factorial central composite design (CCD). The mixture of 10 mL of methanol and 7 mL of water (pH 2.2) (three times) was chosen for the extraction of selected drug from fish tissues. The results showed that the highest recoveries of analytes were obtained with an extraction temperature of 40 °C, ultrasonic power of 300 W, extraction time of 30 min.Under the optimal conditions, the linearity of method was 0.12–5.00 μg/g. The determination coefficients (R²) were from 0.979 to 0.998. The limits of detection (LODs) and limits of quantification (LOQs) for the extracted compounds were 0.04–0.17 μg/g and 0.12–0.50 μg/g, respectively. The recoveries were between 85.5% and 115.8%.     

Optimization of ultrasonic-assisted extraction of pomegranate (Punica granatum L.) seed oil

The effectiveness of ultrasonic-assisted extraction (UAE) of pomegranate seed oil (PSO) was evaluated using a variety of solvents. Petroleum ether was the most effective for oil extraction, followed by n-hexane, ethyl acetate, diethyl ether, acetone, and isopropanol. Several variables, such as ultrasonic power, extraction temperature, extraction time, and the ratio of solvent volume and seed weight (S/S ratio) were studied for optimization using response surface methodology (RSM). The highest oil yield, 25.11% (w/w), was obtained using petroleum ether under optimal conditions for ultrasonic power, extraction temperature, extraction time, and S/S ratio at 140 W, 40 °C, 36 min, and 10 ml/g, respectively. The PSO yield extracted by UAE was significantly higher than by using Soxhlet extraction (SE; 20.50%) and supercritical fluid extraction (SFE; 15.72%). The fatty acid compositions were significantly different among the PSO extracted by Soxhlet extraction, SFE, and UAE, with punicic acid (>65%) being the most dominant using UAE.     

Aqueous ionic liquid based ultrasonic assisted extraction of eight ginsenosides from ginseng root

We developed an aqueous ionic liquid based ultrasonic assisted extraction (ILUAE) method for the extraction of the eight ginsenosides (ginsenoside-Rg1, -Re, -Rf, -Rb1, -Rc, -Rb2, -Rb3 and -Rd) from ginseng root. A series of l-alkyl-3-methylimidazolium ionic liquids differing in composition of anions and cations were evaluated for extraction efficiency. The results indicated that the ILUAE method has a remarkable ability to improve the extraction efficiency of ginsenosides. In addition, the ILUAE procedure was also optimized on some ultrasonic parameters, such as the IL concentration, solvent to solid ratio and extraction time. Under these optimal conditions (e.g., with 0.3 M [C₃MIM]Br, solvent to solid ratio of 10:1 and extraction time of 20 min), this approach gained the highest extraction yields of total ginsenosides 17.81 ± 0.47 mg/g. Compared with the regular UAE, the proposed approach exhibited 3.16 times higher efficiency and 33% shorter extraction time, which indicated that ILUAE has a broad prospect for sample preparation of medicinal plants.     

Effect of acoustic frequency and power density on the aqueous ultrasonic-assisted extraction of grape pomace (Vitis vinifera L.) – A response surface approach

Aqueous ultrasound-assisted extraction (UAE) of grape pomace was investigated by Response Surface Methodology (RSM) to evaluate the effect of acoustic frequency (40, 80, 120 kHz), ultrasonic power density (50, 100, 150 W/L) and extraction time (5, 15, 25 min) on total phenolics, total flavonols and antioxidant capacity. All the process variables showed a significant effect on the aqueous UAE of grape pomace (p < 0.05). The Box–Behnken Design (BBD) generated satisfactory mathematical models which accurately explain the behavior of the system; allowing to predict both the extraction yield of phenolic and flavonol compounds, and also the antioxidant capacity of the grape pomace extracts. The optimal UAE conditions for all response factors were a frequency of 40 kHz, a power density of 150 W/L and 25 min of extraction time. Under these conditions, the aqueous UAE would achieve a maximum of 32.31 mg GA/100 g fw for total phenolics and 2.04 mg quercetin/100 g fw for total flavonols. Regarding the antioxidant capacity, the maximum predicted values were 53.47 and 43.66 mg Trolox/100 g fw for CUPRAC and FRAP assays, respectively. When comparing with organic UAE, in the present research, from 12% to 38% of total phenolic bibliographic values were obtained, but using only water as the extraction solvent, and applying lower temperatures and shorter extraction times. To the best of the authors’ knowledge, no studies specifically addressing the optimization of both acoustic frequency and power density during aqueous-UAE of plant materials have been previously published.     

High coercivity Nd2(Fe,Co)14C-type ribbons prepared by melt spinning

Melt-spun Nd₁₃Dy₂Fe_77−xCo_xC₆B₂ (x=0, 5, 10, 15, 20) ribbons with a high coercivity more than 2 T have been obtained. It was found that the ribbons quenched at the optimum wheel speed 15 m/s (as-spun ribbons) mainly consist of ferromagnetic 2 : 14 : 1 phase and paramagnetic NdC₂ phase, and the ribbons spun at 25 m/s and subsequently annealed at 973 K for 15 min (as-annealed ribbons) are primarily composed of the magnetic 2 : 14 : 1 and 2 : 17 phases. The magnetization process of as-spun ribbons controlled by a pinning of the domain wall is different from that of as-annealed ribbons determined by a nucleation of the reverse domain. This significant difference originates possibly from the existence of paramagnetic NdC₂ phase acting as a pinning center in as-spun ribbons. In the as-annealed ribbons, the substitution of Co for Fe leads to increase of remanence (μ₀M_r), maximum energy product ((BH)_max) from 0.67 T, 9.7 MGOe for x=0 to 0.84 T, 14.4 MGOe for x=10, respectively. A coercivity of 2.74 T is obtained for as-quenched Nd₁₃Dy₂Fe_77−xCo_xC₆B₂ (x=0) ribbons.     

Tuneability of Sm(1 − x)CexFeO3 ± λ perovskites: Thermal stability and electrical conductivity

Trimetallic perovskite oxides, Sm_(1 ? x)Ce_xFeO_3 ± λ (x = 0–0.05), were prepared by thermal decomposition of amorphous citrate precursors followed by calcinations. The material properties of the substituted perovskites were characterized by X-ray diffraction (XRD), X-ray florescence spectroscopy (XRF), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The doped materials exhibited a single perovskite phase in air up to 1350 °C and have specific surface areas in the range of 2.696–8.665 m²/g. In reducing atmosphere (5%v/vH₂/N₂), the unsubstituted perovskite (x = 0) decomposed into two phases while the ceria stabilized materials (x = 0.01, x = 0.03, x = 0.05) remained in a single phase as revealed by XRD analysis. Their conductivities were measured by the four point probe method in air and in dilute hydrogen (5%v/vH₂/N₂) separately. The ceria substituted materials show increased stability versus reduction and phase separation for a wide temperature range (up to 1000 °C). Although undoped SmFeO₃ has higher conductivity under oxidizing conditions than ceria doped SmFeO₃ due its p-type nature, the situation is reversed under reducing conditions. The ceria substituted perovskites (Sm_(1 ? x)Ce_xFeO_3 ± λ, x = 0–0.05) showed higher conductivity in reducing than in oxidizing conditions, suggesting that ceria doping at the A-site has changed the SmFeO₃ from p-type to n-type semi-conducting behavior.     

Mapping of an ultrasonic bath for ultrasound assisted extraction of mangiferin from Mangifera indica leaves

The present work deals with the mapping of an ultrasonic bath for the maximum extraction of mangiferin from Mangifera indica leaves. I₃⁻ liberation experiments (chemical transformations) and extraction (physical transformations) were carried out at different locations in an ultrasonic bath and compared. The experimental findings indicated a similar trend in variation in an ultrasonic bath by both these methods. Various parameters such as position and depth of vessel in an ultrasonic bath, diameter and shape of a vessel, frequency and input power which affect the extraction yield have been studied in detail. Maximum yield of mangiferin obtained was approximately 31 mg/g at optimized parameters: distance of 2.54 cm above the bottom of the bath, 7 cm diameter of vessel, flat bottom vessel, 6.35 cm liquid height, 122 W input power and 25 kHz frequency. The present work indicates that the position and depth of vessel in an ultrasonic bath, diameter and shape of a vessel, frequency and input power have significant effect on the extraction yield. This work can be used as a base for all ultrasonic baths to obtain maximum efficiency for ultrasound assisted extraction.     

The initial growth structure of Ni1-xFex (x=0.6–0.8) films dc-biased plasma-sputter-deposited on Ni/MgO(0 0 1), and on Fe/MgO(0 0 1)

Cross sectional and plane-view transmission electron microscopy (X- and PV-TEM) were used to investigate the initial growth phase of 5, 10, 20 and 40 nm thick Ni_1-xFe_x (x=0.6–0.8) films, prepared on MgO(0 0 1) covered with a buffer layer of Fe or Ni as well as on naked MgO(0 0 1). The 100 nm thick buffer layers of Fe and Ni were pre-grown on MgO(0 0 1). All of Ni_0.20Fe_0.80, Ni_0.40Fe_0.60, Fe and Ni films could be epitaxially grown at 250°C by dc-biased plasma sputtering at 2.9 kV in pure Ar gas.The films of Ni_0.20Fe_0.80 and Ni_0.40Fe_0.60 were grown in their own stable phase, bcc and fcc on MgO(0 0 1), respectively. However, Ni_0.20Fe_0.80 film could be grown in fcc phase pseudomorphic with Ni(0 0 1) up to 20 nm thick on Ni/MgO(0 0 1), while Ni_0.40Fe_0.60 film in bcc phase pseudomorphic with Fe(0 0 1) up to 10 nm thick on Fe/MgO(0 0 1). With increasing thickness, their growth phases transformed into their own stable phases. Whether or not the pseudomorphic phase may be induced and what its critical thickness may be should depend primarily on the lattice misfit between the crystal planes in contact. The growth mode of Ni_0.40Fe_0.60 film was investigated more in details to be compared with the simulations of the average strain energy versus thickness and with those of the critical thickness of the pseudomorphic films versus the lattice misfit between the contacted crystal planes.     

Effect of ultrasonic treatment on total phenolic extraction from Lavandula pubescens and its application in palm olein oil industry

The aims of the current study were to evaluate the best technique for total phenolic extraction from Lavandula pubescens (Lp) and its application in vegetable oil industries as alternatives of synthetic food additives (TBHQ and BHT). To achieve these aims, three techniques of extraction were used: ultrasonic-microwave (40 kHz, 50 W, microwave power 480 W, 5 min), ultrasonic-homogenizer (20 kHz, 150 W, 5 min) and conventional maceration as a control. By using the Folin–Ciocalteu method, the total phenolic contents (TPC) (mg gallic acid equivalent/g dry matter) were found to be 253.87, 216.96 and 203.41 for ultrasonic-microwave extract, ultrasonic-homogenizer extract and maceration extract, respectively. The ultrasonic-microwave extract achieved the higher scavenger effect of DPPH (90.53%) with EC₅₀ (19.54 μg/mL), and higher inhibition of β-carotene/linoleate emulsion deterioration (94.44%) with IC₅₀ (30.62 μg/mL). The activity of the ultrasonic-microwave treatment could prolong the induction period (18.82 h) and oxidative stability index (1.67) of fresh refined, bleached and deodorized palm olein oil (RBDPOo) according to Rancimat assay. There was an important synergist effect between citric acid and Lp extracts in improving the oxidative stability of fresh RBDPOo. The results of this work also showed that the ultrasonic-microwave assisted extract was the most effective against Gram-positive and Gram-negative strains that were assessed in this study. The uses of ultrasonic-microwave could induce the acoustic cavitation and rupture of plant cells, and this facilitates the flow of solvent into the plant cells and enhances the desorption from the matrix of solid samples, and thus would enhance the efficiency of extraction based on cavitation phenomenon.     

Phase stability and oxygen non-stoichiometry of SrCo0.8Fe0.2O3−δ measured by in situ neutron diffraction

The phase stability, oxygen stoichiometry and expansion properties of SrCo_0.8Fe_0.2O_3−δ (SCF) were determined by in situ neutron diffraction between 873 and 1173 K and oxygen partial pressures of 5 × 10^− 4 to 1 atm. At a pO₂ of 1 atm, SCF adopts a cubic perovskite structure, space group Pm3¯m, across the whole temperature range investigated. At a pO₂ of 10^− 1 atm, a two-phase region exists below 922 K, where the cubic perovskite phase coexists with a vacancy ordered brownmillerite phase, Sr₂Co_1.6Fe_0.4O₅, space group Icmm. A pure brownmillerite phase is present at pO₂ of 10^− 2 and 5 × 10^− 4 atm below 1020 K. Above 1020 K, the brownmillerite phase transforms to cubic perovskite through a two-phase region with no brownmillerite structure observed above 1064 K. Large distortion of the BO₆ (B = Co, Fe) octahedra is present in the brownmillerite structure with apical bond lengths of 2.2974(4) Å and equatorial bond lengths of 1.9737(3) Å at 1021 K and a pO₂ of 10^− 2 atm. SCF is highly oxygen deficient with a maximum oxygen stoichiometry, 3 − δ, measured in this study of 2.58(2) at 873 K and a pO₂ of 1 atm and a minimum of 2.33(2) at 1173 K and a pO₂ of 5 × 10^− 4 atm. Significant differences in lattice volume and expansion behavior between the brownmillerite and cubic perovskite phases suggest potential difficulties in thermal cycling of SrCo_0.8Fe_0.2O_3−δ membranes.     

Environmental friendly cold-mechanical/sonic enzymatic assisted extraction of genipin from genipap (Genipa americana)

An efficient cold-mechanical/sonic-assisted extraction technique was developed for extraction of genipin from genipap (Genipa americana) peel. Ultrasound assisted extraction (285 W, 24 kHz) was performed at 5, 10 and 15 °C for 5, 10 and 15 min. After cold-extraction, genipin was separated from pectin and proteins by aid of fungal pectinesterase. The maximum yield of non-cross-linked genipin was 7.85 ± 0.33 mg/g, at 10 °C for 15 min by means of ultrasound extraction. The protein amount in extracts decreased in all samples. If mechanical process is combined with ultrasound assisted extraction the yield is increased by 8 times after the pectinesterase-assisted polyelectrolyte complex formation between pectic polysaccharides and proteins, avoiding the typical cross-linking of genipin. This novel process is viable to obtain non-cross-linked genipin, to be used as a natural colorant and cross-linker in the food and biotechnological industries.     

Adsorption of chlorine on Ru(0001)—A combined density functional theory and quantitative low energy electron diffraction study

Chlorine adsorption on Ru(0001) surface has been studied by a combined density functional theory (DFT) and quantitative low energy electron diffraction (LEED) approach. The (√3 × √3)R30°-Cl phase with Θ_Cl = 1/3 ML and chlorine sitting in fcc sites has been identified by DFT calculations as the most stable chlorine adsorbate structure on Ru(0001) with an adsorption energy of ? 220 kJ/mol. The atomic geometry of (√3 × √3)R30°-Cl was determined by quantitative LEED. The achieved agreement between experimental and simulated LEED data is quantified by a Pendry factor of r_P = 0.19 for a fcc adsorption site with a Cl-Ru bond length of 2.52 Å. At chlorine coverages beyond 1/3 ML LEED reveals diffuse diffraction rings, indicating a continuous compression of the hexagonal Cl overlayer with a preferred average Cl–Cl distance of 4.7 Å in the (√3 × √3)R30°-Cl, Θ_Cl = 1/3 ML phase towards 3.9 Å at saturation coverage of 0.48 ML.     

Aqueous ionic liquid based ultrasonic assisted extraction of four acetophenones from the Chinese medicinal plant Cynanchum bungei Decne

In this study, an aqueous ionic liquid based ultrasonic assisted extraction (ILUAE) method for the extraction of the four acetophenones, namely 4-hydroxyacetophenone (1), 2,5-dihydroxyacetophenone (2), baishouwubenzophenone (3) and 2,4-dihydroxyacetophenone (4) from the Chinese medicinal plant Cynanchum bungei was developed. Three kinds of aqueous l-alkyl-3-methylimidazolium ionic liquids with different anion and alkyl chain were investigated. The results indicated that ionic liquids (ILs) showed remarkable effects on the extraction efficiency of acetophenones. In addition, the ILUAE, including several ultrasonic parameters, such as the ILs concentration, solvent to solid ratio, power, particle size, temperature, and extraction time have been optimized. Under these optimal conditions (e.g., with 0.6 M [C₄MIM]BF₄, solvent to solid ratio of 35:1, power of 175 W, particle size of 60–80 mesh, temperature of 25 °C and time of 50 min), this approach gained the highest extraction yields of four acetophenones 286.15, 21.65, 632.58 and 205.38 μg/g, respectively. The proposed approach has been evaluated by comparison with the conventional heat-reflux extraction (HRE) and regular UAE. The results indicated that ILUAE is an alternative method for extracting acetophenones from C. bungei.     

Influence of fabrication processing on phase transition and electrical properties of 0.8Pb(Zr1/2Ti1/2)O3–0.2Pb(Ni1/3Nb2/3)O3 ceramics

The binary system of 0.8Pb(Zr_1/2Ti_1/2)O₃–0.2Pb(Ni_1/3Nb_2/3)O₃ ceramics were synthesized by conventional mixed oxide and columbite method. X-ray diffraction analysis demonstrated the coexistence of both the rhombohedral and tetragonal phases for the columbite prepared sample. Rhombohedral to tetragonal phase transition for columbite method was different compared with those of the mixed oxide method. The permittivity shows a shoulder at the rhombohedral to tetragonal phase transition temperature T_Rho–Tetra = 195 °C, and then a maximum permittivity (36,000 at 10 kHz) at the transition temperature T_m = 277 °C on ceramics prepared with the columbite method. However, piezoelectric coefficient (d₃₃) was measured to be 282 pC/N for the conventional method and higher than the columbite method. The results were related to the phase compositions and porosity of the ceramics.