Topotactical reactions with ferrimagnetic oxides having hexagonal crystal structures—I
TL;DR: In this article, a new method is described for the preparation of polycrystalline materials with oriented crystals by reaction of the oriented grains of a strongly anisotropic ferrimagnetic with non-oriented grains of usually non-magnetic components.
About: This article is published in Journal of Inorganic and Nuclear Chemistry.The article was published on 1959-02-01. It has received 1850 citations till now. The article focuses on the topics: Spinel & Ferrimagnetism.
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TL;DR: A lead-free piezoelectric ceramic with an electric-field-induced strain comparable to typical actuator-grade PZT is reported, achieved through the combination of the discovery of a morphotropic phase boundary in an alkaline niobate-based perovskite solid solution, and the development of a processing route leading to highly textured polycrystals.
Abstract: Lead has recently been expelled from many commercial applications and materials (for example, from solder, glass and pottery glaze) owing to concerns regarding its toxicity. Lead zirconium titanate (PZT) ceramics are high-performance piezoelectric materials, which are widely used in sensors, actuators and other electronic devices; they contain more than 60 weight per cent lead. Although there has been a concerted effort to develop lead-free piezoelectric ceramics, no effective alternative to PZT has yet been found. Here we report a lead-free piezoelectric ceramic with an electric-field-induced strain comparable to typical actuator-grade PZT. We achieved this through the combination of the discovery of a morphotropic phase boundary in an alkaline niobate-based perovskite solid solution, and the development of a processing route leading to highly textured polycrystals. The ceramic exhibits a piezoelectric constant d33 (the induced charge per unit force applied in the same direction) of above 300 picocoulombs per newton (pC N(-1)), and texturing the material leads to a peak d33 of 416 pC N(-1). The textured material also exhibits temperature-independent field-induced strain characteristics.
4,689 citations
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...1b for the textured ceramics LF3T and LF4T, for which the Lotgering's factor...
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TL;DR: The most important members of the hexaferrite family are shown below, where Me = a small 2+ ion such as cobalt, nickel, or zinc, and Ba can be substituted by Sr: • M-type ferrites, such as BaFe12O19 (BaM or barium ferrite), SrFe 12O19(SrM or strontium ferite), and cobalt-titanium substituted M ferrite, Sr- or BaFe 12−2xCoxTixO19, or CoTiM as discussed by the authors.
1,855 citations
TL;DR: In this article, the dielectric, ferroelectric and piezoelectric properties of perovskite and bismuth layer-structured BLSF (BLSF) ceramics are described as superior candidates for lead-free, lead free, and low-cost piezolectric materials to reduce environmental damages.
Abstract: Dielectric, ferroelectric and piezoelectric properties of perovskite ferroelectric and bismuth layer-structured ferroelectric (BLSF) ceramics are described as superior candidates for lead-free piezoelectric materials to reduce environmental damages. Perovskite type ceramics seem to be suitable for actuator and high power applications that are required a large piezoelectric constant, d 33 (>300 pC/N) and a high Curie temperature, T c (>200 °C). For BaTiO 3 (BT)-based solid solutions, that is, (1 − x )BaTiO 3 − x (Bi 0.5 K 0.5 )TiO 3 [BTBK − 100 x ] ceramics, the T c increases with increasing the amount of x . BTBK-20 + MnCO 3 0.1 wt.% ceramic shows the high T c than 200 °C and the electromechanical coupling factor, k 33 = 0.35. In the case of a (Bi 1/2 Na 1/2 )TiO 3 − b BaTiO 3 − c (Bi 1/2 K 1/2 )TiO 3 [BNBK (100 a /100 b /100 c )] solid solution ceramics, the d 33 and T c are 191 pC/N and 301 °C for the BNBK (85.2/2.8/12), respectively. On the other hand, BLSF ceramics seem to be excellent candidates as piezoelectric sensors for high temperatures and ceramic resonators with high mechanical quality factor ( Q m ), and low temperature coefficient of resonance frequency (TC- f r ). Donor-doped Bi 4 Ti 3 O 12 ceramics such as Bi 4 Ti 3− x Nb x O 12 [BITN- x ] and Bi 4 Ti 3− x V x O 12 [BITV- x ] show high T c than 650 °C. The k 33 value of the grain-oriented (HF) BITN-0.08 ceramic is 0.39 and is able to keep the same value up to 350 °C. Bi 3 TiTaO 9 (BTT)-based solid solution system, Sr x −1 Bi 4− x Ti 2− x Ta x O 9 [SBTT2( x )] (1 ≦ x ≦ 2), displays the high Q m value (=13500) in (p)-mode at the x = 1.25 composition.
742 citations
TL;DR: A facile development of highly efficient Pt-TiO(2) nanostructured films via versatile gas-phase deposition methods is described, where the size of the Pt NPs and the unique 1D structure of TiO( 2) single crystals played an important role.
Abstract: A facile development of highly efficient Pt-TiO2 nanostructured films via versatile gas-phase deposition methods is described. The films have a unique one-dimensional (1D) structure of TiO2 single crystals coated with ultrafine Pt nanoparticles (NPs, 0.5–2 nm) and exhibit extremely high CO2 photoreduction efficiency with selective formation of methane (the maximum CH4 yield of 1361 μmol/g-cat/h). The fast electron-transfer rate in TiO2 single crystals and the efficient electron–hole separation by the Pt NPs were the main reasons attributable for the enhancement, where the size of the Pt NPs and the unique 1D structure of TiO2 single crystals played an important role.
667 citations
TL;DR: In this paper, the origin of ferromagnetism in ZnO-based systems was investigated using Co-doped ZnOs thin films as prototypical examples of II-VI-based diluted magnetic semiconductors.
Abstract: The origin of ferromagnetism in ZnO-based systems was investigated using Co-doped ZnO thin films as prototypical examples of II–VI-based diluted magnetic semiconductors. In spite of the atomic-scale dissolution of Co ions in wurtzite ZnO, both the magnetization-temperature curve and the magnetization-field curve demonstrated that Zn1−xCoxO thin films were paramagnetic for x⩽0.12. On the other hand, Zn1−xCoxO films with x greater than 0.12 were characterized by the Co-metal clustering and apparently showed room-temperature ferromagnetism. The discrepancy between the zero-field cooling and the field cooling curves further indicates that Co-doped ZnO films (for x>0.12) are superparamagnetic and the observed ferromagnetism originates from the nanometer-sized Co clusters.
605 citations
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