Journal of the American Ceramic Society

Wu, Jiagang; Wang, John

doi: 10.1111/j.1551-2916.2010.03661.xpmid: N/A

Bilayered thin films consisting of (Bi0.90La0.10)FeO3 and Bi(Fe0.95Mn0.05)O3, i.e., Bi(Fe0.95Mn0.05)O3/(Bi0.90La0.10)FeO3, were deposited on SrRuO3 buffered SrTiO3(111) substrates by off‐axis radio frequency magnetic sputtering, where (111)‐oriented bilayered thin films were obtained. The bilayered Bi(Fe0.95Mn0.05)O3/(Bi0.90La0.10)FeO3 thin film possesses a lower coercive field (2Ec∼335.6 kV/cm) and a larger remanent polarization (2Pr∼155.2 μC/cm2) at room temperature, and a higher relative permittivity as compared with those of single‐layer (Bi0.90La0.10)FeO3 and Bi(Fe0.95Mn0.05)O3 thin films, together with an improvement of the magnetic properties (2Ms∼31.2 emu/cm3). The bottom (Bi0.90La0.10)FeO3 nanolayer promotes the growth of the Bi(Fe0.95Mn0.05)O3 layer, which are largely responsible for the multiferroic behavior observed.

Yang, Jinshan; Dong, Shaoming; Ding, Yusheng; Wang, Zhen; Zhou, Haijun; Lu, Bo

doi: 10.1111/j.1551-2916.2010.03672.xpmid: N/A

High‐purity titanium silicon carbide powders were fabricated by an in situ reaction of polycarbosilane and metal titanium. The effects of the starting reagents and the pyrolysis temperature on the fabrication of high‐purity Ti3SiC2 were studied. The results showed that high‐purity Ti3SiC2 could be obtained when the atomic ratio of Ti:Si was 3:1.5 and the effect of the temperature of pyrolysis on the purity of the powders was insignificant. The atomic ratio of Ti:Si was calculated on the basis of the empirical formula of SiC2.5H7.

Lan, Jinle; Lin, Yuan‐Hua; Fang, Hui; Mei, Ao; Nan, Ce‐Wen; Liu, Yong; Xu, Shaoliang; Peters, Matthew

doi: 10.1111/j.1551-2916.2010.03673.xpmid: N/A

Gd‐doped CaMnO3 were synthesized by two methods: a coprecipitation route and a conventional solid‐state reaction. The ceramic samples obtained by the coprecipitation method possess nanometer‐scale grains but the grain sizes by the solid‐state reaction route are several micrometers. Our results show that the electrical conductivity is slightly decreased with a decreasing grain size, which indicates that fine‐grained ceramics can maintain good electrical property. However, thermal conductivity values of the fine‐grained sample are relatively low due to the enhancement of grain boundary scattering. The highest dimensionless figure of merit ZT=0.24 has been obtained at 973 K in the air for fine‐grained Ca0.96Gd0.04MnO3, suggesting that they can be a promising candidate of n‐type material for high‐temperature thermoelectric application.

Yoon, Woon‐Ha; Ryu, Jungho; Choi, Jong‐Jin; Hahn, Byung‐Dong; Choi, Joon Hwan; Lee, Byoung‐Kuk; Cho, Jae‐Hyung; Park, Dong‐Soo

doi: 10.1111/j.1551-2916.2010.03674.xpmid: N/A

Calcium cobaltite (Ca3Co4O9; CCO349) films with a c‐axis texture and a thickness of 60 μm were fabricated by aerosol deposition (AD). The films exhibited superior characteristics to those grown by other methods. The pole figure measurements indicated that almost 65% of the films had their c‐axis tilted from the surface normal by 30°. The Seebeck voltage and resistivity of the films in the measurement range between room temperature and 900 K were 175 μV/K and <20 mΩ·cm, respectively. Based on these results, the AD‐CCO349 film is a promising material for thermoelectric generation.

Ruan, Wei; Li, Guorong; Zeng, Jiangtao; Bian, Jianjiang; Kamzina, Liudmila S.; Zeng, Huarong; Zheng, Liaoying; Ding, Aili

doi: 10.1111/j.1551-2916.2010.03675.xpmid: N/A

Highly transparent ceramics of La‐doped 0.75Pb(Mg1/3Nb2/3)O3–0.25PbTiO3 were fabricated by a two‐stage sintering method from conventional raw materials. The ceramics exhibited a transparency as high as 65% for the infrared wavelength. Large quadratic electro‐optic coefficient of 66 × 10−16 (m/v)2 was obtained, which was the highest value reported so far in Pb(Mg1/3Nb2/3)O3–PbTiO3 ceramics. The ferroelectric phase inducing the threshold electric field Eth and the domain structure of the transparent ceramics were studied.

Joung, Mi‐Ri; Kim, Jin‐Seong; Song, Myung‐Eun; Nahm, Sahn; Paik, Jong‐Hoo

doi: 10.1111/j.1551-2916.2010.03676.xpmid: N/A

The addition of Li2CO3 to Sr2V2O7 ceramics decreased their sintering temperature and time. A dense microstructure was developed for the specimens sintered at 750°–850°C due to the melting of Li2CO3 during the sintering. For the specimens sintered at 800°C, the grain size was considerably increased when the Li2CO3 content exceeded 1.0 mol%. The Q×f value was increased by the Li2CO3 addition due to the increased density and grain size. In particular, a high Q×f value of 73 800 GHz with ɛr and τf values of 9.94 and −28.8 ppm/°C, respectively, was obtained for the specimen containing 3.0 mol% Li2CO3 sintered at 800°C for 2h.

Yang, Lihui; Wang, Genshui; Dong, Xianlin; Rémiens, Denis

doi: 10.1111/j.1551-2916.2010.03677.xpmid: N/A

A series of ultrathin TiOx (0–12 nm) seeded (Ba,Sr)TiO3 (BST) thin films have been prepared on Pt (111)/TiOx/SiO2/Si substrates by RF‐magnetron sputtering. Experimental results show that an ultrathin TiOx layer acts as an initial template for the BST films in the first nucleation stage, resulting in a significant influence on crystalline orientation and electrical characteristics of the resultant BST films. Interestingly, highly (111) oriented BST film [α(111)∼97%] with 5‐nm‐thick TiOx seeding layer exhibits a shifted Curie temperature (Tc=275 K) and an enhanced tunability of 61.16% at 400 kV/cm, when compared with (001)‐oriented BST without TiOx layer (Tc=250 K and tunability=50.05%).

Masuda, Yoshitake; Ohji, Tatsuki; Kato, Kazumi

doi: 10.1111/j.1551-2916.2010.03680.xpmid: N/A

Tin oxide nanocrystals with high surface area were first synthesized in aqueous solutions at 50°C. The Brunauer–Emmett–Teller (BET) surface area successfully reached 194 m2/g. It was much higher than that of SnO2 (BET 47.2 m2/g), SnO2 (BET 25.9 m2/g), SnO2 (BET 23 m2/g), and In2O3–SnO2 (BET 3–6 m2/g). N2 adsorption characteristics revealed that they had pores of 1–3 nm, which contributed to the high surface area. Transmission electron microscopy, electron diffraction, and X‐ray diffraction indicated the morphology, crystal structure, and chemical composition of nanocrystals. Novel process allowed us to avoid sintering and deformation of the crystals, and hence realized a high surface area and unique morphology.

Igawa, Naoki; Taguchi, Tomitsugu; Fukazawa, Hiroshi; Yamauchi, Hiroki; Utsumi, Wataru

doi: 10.1111/j.1551-2916.2010.03688.xpmid: N/A

The neutron powder diffraction measurement of LiCo1/3Ni1/3Mn1/3O2 was carried out and the crystal structure and scattering density distribution were analyzed by Rietveld refinement and the maximum entropy method (MEM) to estimate the Li diffusing pathway. Rietveld refinement showed that the structure was basically the same as LiCoO2: a R‐3m space group, with Li and O mainly occupying the 3a and 6c sites, and Co, Ni, and Mn randomly occupying the 3b site. Approximately 4% of the Li and Ni atoms exchanged their original sites (3a and 3b) to occupy 3b and 3a, respectively. Based on MEM analyses, we surmise that Li atoms moved on the (001), (003), and (00‐3) planes and diffused through the 3a–9e–3a sites on these planes.