Controlled Atmosphere Thermal Treatment for Pyrochlore Phase Elimination of PMN-PT/CFO Prepared by Spark Plasma Sintering

2014 ◽  
Vol 975 ◽  
pp. 274-279 ◽  
Author(s):  
Diego Seiti Fukano Viana ◽  
José Antônio Eiras ◽  
William Junior Nascimento ◽  
Fabio Luiz Zabotto ◽  
Ducinei Garcia

Multiferroics are interesting materials which present more than one ferroic property and have a great potential for practical applications [,,]. In addition, the coupling of magnetic and electric properties, the magnetoelectric effect (ME), offers news possibilities to applications [2,]. The magnetoelectric effect can be observed in single-phase materials like LuFe2O4, BiFeO3, etc. [1,] or in composites like PMN-PT/CFO, BaTiO3/CoFe2O4, etc. The ME composites have advantages over single-phase materials. They are easier to fabricate, less expensive, and have a wider range of working temperatures than single-phase materials []. However, some parameters that enhance the ME response need to be optimized. These parameters are the composition, the microstructure (grain size, grain orientation) and sintering parameters [6]. Thus, this work attempts to create a synthesis protocol to prepare the ME composite PMN-PT/CFO by Spark Plasma Sintering (SPS) keeping the average grain size as small as possible.

2002 ◽  
Vol 17 (3) ◽  
pp. 575-581 ◽  
Author(s):  
Tomonari Takeuchi ◽  
Claudio Capiglia ◽  
Nalini Balakrishnan ◽  
Yasuo Takeda ◽  
Hiroyuki Kageyama

Dense BaTiO3 ceramics consisting of fine grains were prepared using fine powder (average grain size of 0.06 μm; BT006) as a starting material and the spark plasma sintering (SPS) method. The powder was densified to >95% of theoretical x-ray density by the SPS process, and the average grain size of the resulting ceramics was <0.5 μm; the particle size of the initial powder significantly affects the grain size of the resulting SPS pellets. Fixed-frequency (100 kHz), room-temperature permittivity measurements of the BT006-SPS ceramics showed relatively low values (3000–3500) compared with those (typically 5000) for SPS ceramics consisting of larger grains (approximately 1 μm). Lower permittivity was attributed to poor development of ferroelectric domains in the ceramics, which originated from incomplete development of the tetragonal structure as well as the presence of a local orthorhombic structure.


2004 ◽  
Vol 449-452 ◽  
pp. 1109-1112 ◽  
Author(s):  
No Jin Park ◽  
Suck Jong Lee ◽  
In Sung Lee ◽  
Kyeong Sik Cho ◽  
Sung Jin Kim

In order to control the grain size of Cu-15.0Zn-8.1Al shape memory alloy, the spark plasma sintering (SPS) technique was applied. The sintering processes were carried out under different atmospheres with a different powder size. The sintered bodies were denser under the Ar+4%H2 gas atmosphere than under the 100% Ar gas. By using the small-sized powders, the fine microstructure with average grain size of 2~3􀀀 was obtained. With the large-sized powders, the single martensitic phase was observed with the average grain size of 70~72􀀀 . When the starting powders with different sizes were mixed, it is confirmed that the average grain size of the manufactured alloys was 15􀀀 , but the distribution of grain size was not uniform.


2006 ◽  
Vol 510-511 ◽  
pp. 1022-1025 ◽  
Author(s):  
Mikinori Hotta ◽  
Junichi Hojo

Sub-micron and nano-sized β-SiC powders were sintered with AlN and Y2O3 as sintering additives by spark plasma sintering (SPS). The sintered densities reached >95% of theoretical with a different molar ratio of AlN to Y2O3 at total amount of 10vol% and temperature of 1900oC for 10min in N2 atmosphere under a pressure of 30MPa. With increasing amount of the AlN additive, the size of SiC grains decreased and the shape changed from globular to columnar. The fully densified SiC at AlN:Y2O3=95:5mol% had an average grain size of 0.5-1µm and 50-100nm in diameter by using sub-micron and nano-sized SiC starting powders, respectively. Flexural strength of the specimen having grain size of 0.5-1µm was approximately 1200MPa at room temperature.


2021 ◽  
Vol 1035 ◽  
pp. 663-667
Author(s):  
Li Qiong An ◽  
Rong Wei Shi ◽  
Run Hua Fan ◽  
Takashi Goto

Y2Ti2O7 transparent ceramic was fabricated by reactive sintering using spark plasma sintering at 1673 K for 2.7 ks. The sintered body exhibited a cubic pyrochlore structure and uniform microstructure with an average grain size of 2.9 μm. The transmittance reached 73% at a wavelength of 2000 nm after annealing at 1023 K for 21.6 ks.


2007 ◽  
Vol 336-338 ◽  
pp. 834-837 ◽  
Author(s):  
Wei Shu Liu ◽  
Bo Ping Zhang ◽  
Jing Feng Li ◽  
Heng Wang

Single-phase polycrystalline CoSb3 skutterudite was prepared through a new combination of mechanical alloying (MA) and spark plasma sintering (SPS). In order to investigate the influence of MA conditions on the microstructure and thermoelectric properties, MA synthesis were carried out under various conditions with different milling times. The powder sample MAed for 6h still consisted of metal Sb, and then transformed to CoSb3 with a little amount of metal Sb and CoSb2 phases after MA for 15h. Further prolonging the MA time resulted in the decomposition of CoSb3 to CoSb2 phase. The average grain size of the SPSed samples decreased from 650nm to 250nm as MA-time was prolonged from 6 to 24h. Lattice parameters estimated form XRD patterns increase with the increasing MA time. All samples SPSed at 600°C for holding 5 min show an n-type conduction. The electrical resistivity was 1030, 895, 410, 260 μm for the samples from the MA-derived powders with MA-time of 6, 15, 24 and 33h at room temperature, respectively, then reduced to 60 μm at 400°C for all samples. An optimum MA time is 24 h in which the sample shows the highest power factor 612μW/m*K2 at 150°C.


2004 ◽  
Vol 19 (9) ◽  
pp. 2527-2531 ◽  
Author(s):  
Rachman Chaim ◽  
Zhijian Shen ◽  
Mats Nygren

We investigated superfast densification of nanocrystalline MgO powders by spark plasma sintering (SPS) between 700 °C and 825 °C under applied pressures of 100and 150 MPa. Fully-dense transparent nanocrystalline MgO with a 52-nm average grain size was fabricated at 800 °C and 150 MPa for 5 min. In-line transmissionsof 40% and 60% were measured compared to MgO single crystal, for the yellowand red wavelengths, respectively. Densification occurs by particles sliding over each other; the nanometric grain size and pores lead to the optical transparency. The light brownish color of the nanocrystalline MgO is due to the oxygen vacancy color centers, originating from the reducing atmosphere of the SPS process.


2013 ◽  
Vol 647 ◽  
pp. 758-761
Author(s):  
Ping Fu ◽  
Wen Zhong Lu ◽  
Wen Lei ◽  
Yong Xu ◽  
Xian Long Lu

Transparent polycrystalline MgAl2O4ceramics were fabricated by using spark plasma sintering (SPS) technique at a temperature range from 1275 °C to 1400 °C. The average grain size of the samples fabricated at optimal sintering processes was 345 nm. The in-line transmittance of the sintered ceramics can be as high as 70% at 550 nm and 82% at 2000 nm, respectively. The optimal microwave dielectric properties (εr = 8.38, Q×f = 54000 GHz and τf = -74 ppm/°C) were achieved at 1325°C for 20 min.


2011 ◽  
Vol 484 ◽  
pp. 135-138 ◽  
Author(s):  
Li Qiong An ◽  
Akihiko Ito ◽  
Takashi Goto

Transparent La2Zr2O7 with cubic pyrochlore structure was first fabricated by reactive spark plasma sintering using commercially available La2O3 and ZrO2 powders. Single phase of pyrochlore La2Zr2O7 was obtained at a sintering temperature of 1673 K and sintering pressure at 100 MPa for 2.7 ks. The La2Zr2O7 sintered body had a uniform grain size of 1.5 m and exhibited 68% transmittance in the wavelength range of 4–6 m.


2011 ◽  
Vol 412 ◽  
pp. 336-339 ◽  
Author(s):  
Zhen Hua Liu ◽  
Qin Ma ◽  
Jin Jun Lu

Al2O3 ceramic is prepared by spark plasma sintering (SPS) using two commercial α-Al2O3 powders at elevated sintering temperature. The relative density and average grain size of the prepared Al2O3 ceramics are measured and compared. One α-Al2O3 powder has good sintering property because the relative density of the prepared α-Al2O3 ceramic is higher than 97% while another α-Al2O3 powder has poor sintering property.


2007 ◽  
Vol 336-338 ◽  
pp. 831-833
Author(s):  
Ying Chu ◽  
Xin Feng Tang ◽  
Ling Wan ◽  
Qing Jie Zhang

CoSb3 with nanoscale was synthesized by Cross-coprecipitation. A precursor consisting of antimony oxide and cobalt hydrate was prepared by the reaction of CoCl2, SbCl3 and both precipitators at room temperature. The precursor was reduced in thermal treatment under hydrogen atmosphere whereby the CoSb3 was thus obtained. The parameters especially reducing temperature and atmosphere (content of H2) influence the constituent phases and particle size of product significantly. The single phase CoSb3 with the average grain size of 60~70 nm was obtained after reduced at 723 K for 2 h with pure H2. Nanoscale CoSb3 powder was used as starting materials, and bulk CoSb3 compound was prepared by spark plasma sintering (SPS). The effect of grains size on thermal conductivity was investigated.


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