Lead-free ferroelectric and piezoelectric ceramics, (Bi0.5Na0.5(1−x)Li0.5x)TiO3 and (1 − y)(Bi0.5Na0.48Li0.02)TiO3–yBaTiO3 (abbreviated as BNLT100x and BNLBT4-100y, respectively), were fabricated by a quenching procedure after sintering, and then their electrical properties were investigated with the aim of increasing their depolarization temperature Td. From the measurements by a resonance–antiresonance method, the electromechanical coupling factors k33 of BNLT100x and BNLBT4-100y were exactly the same after the quenching treatment as compared with the nonquenched one. The Td of all BNLT100x quenched from 1100 °C reached around 240 °C, and they are almost 60 °C higher for x = 0, 0.02, 0.04, and almost 80 °C higher for x = 0.08 than those of nonquenched ceramics. We also found, from the measurement on BNLBT4-100y quenched from 1100 °C, that the Td values were enhanced to higher temperature by the quenching treatment, even in the case of rhombohedral side (100y < 6), tetragonal side (100y > 6), and MPB composition (100y = 6). Moreover, we confirmed that the rhombohedrality 90-α and the tetragonality c/a values were enhanced by the quenching treatment. This result revealed that, even in the tetragonal symmetry, the lattice distortion (tetragonality) could also be stabilized by the quenching treatment in BNT-based solid solution ceramics.
Lead-free piezoelectric ceramics, (1-0.04-x)(Bi0.5Na0.5)TiO3-0.04(Bi0.5Li0.5)TiO3-x(Bi0.5K0.5)TiO3 (abbreviated BNLKT4-100x), were prepared by quenching treatment after sintering, and then their electrical properties and lattice distortion were investigated for the purpose of increasing their depolarization temperature Td. The Td was ∼40 °C higher for x = 0, 0.1, and 0.18 in the rhombohedral structure and at the morphotropic phase boundary composition (MPB), and ∼80 °C higher for x = 0.3 and 0.4 in the tetragonal structure than those of normally cooled samples. The increase in Td was strongly correlated with enlargement for lattice distortion. Td and k33 for quenched BNLKT4-18 in MPB composition exhibited 0.59 °C and 223 °C, respectively. Both of Td and k33 was increased by quenching compared with previously reported values. That is, tread-off relation between Td and k33 was overcame. Moreover, Td elevated above 300 °C for quenched BNLKT4-40 showing tetragonal phase. Therefore, we experimentally revealed a strong correlation between lattice distortion and Td. The quenching is an effective of increasing Td for BNLKT solid-solution systems without the deterioration of their piezoelectric properties.
Two novel, strictly aerobic, sulfur-dependent, thermoacidophilic strains, IC-006T and IC-007, were isolated from a solfataric field at Hakone Ohwaku-dani, Kanagawa, Japan. Cells of the two strains were irregular cocci with a diameter of 1.0–1.8 µm. They were strict aerobes and grew in a temperature range between 45 and 69 °C (optimally at 65 °C) and a pH range between 0.4 and 5.5 (optimally at pH 3.5). They required sulfur or a reduced sulfur compound, and sulfur was oxidized to sulfate. They grew autotrophically or mixotrophically utilizing several sugars and complex organic substances as carbon sources. The DNA G+C content was 42.4 mol%. A comparison of the 16S rRNA gene sequences among members of the order Sulfolobales indicated that they were closely related to Sulfolobus metallicus , forming an independent lineage within this order. The two isolates and Sulfolobus metallicus were also diffentiated based on their phenotypic properties from the other members of the order Sulfolobales . Detailed comparisons of the phenotypic properties and DNA–DNA hybridization study illustrated that the two isolates belong to a species different from Sulfolobus metallicus . On the basis of the phylogenetic and phenotypic comparisons, we propose a new genus and species, Sulfuracidifex tepidarius gen. nov., sp. nov. to accommodate strains IC-006T and IC-007. The type strain of Sulfuracidifex tepidarius is IC-006T (=JCM 16833T=DSM 104736T). In addition, Sulfolobus metallicus should be transferred to the new genus as Sulfuracidifex metallicus comb. nov.: the type strain is Kra23T (=DSM 6482T=JCM 9184T=NBRC 15436T).
Organic materials have attracted attention for thermoelectric materials reusing low-temperature waste heat. For the thermoelectric performance enhancement of organic materials, the introduction of inorganic nanowires is effective due to the percolation effect. In this study, we synthesized Cu 2 Se NWs by the photoreduction method and prepared poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) thin films containing Cu 2 Se NWs by spin-coating PEDOT:PSS and Cu 2 Se NWs alternatively. The composite films exhibited a drastic increase in electrical conductivity at more than 40 wt % Cu 2 Se, and the Cu 2 Se amount threshold was in good agreement with surface structures as observed by a scanning electron microscope. This indicates that the percolation effect of connected Cu 2 Se NWs brought high electrical conductivity. As a result, the composite thin films exhibited a higher power factor than the PEDOT:PSS film. This power factor enhancement by the percolation effect would be expected to contribute to the development of thermoelectric performance enhancement for organic materials.
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