Conventional and Spark Plasma Sintered Ba 0.8 Pb 0.2 TiO 3 Nano Ceramics: Structural, Dielectric, and Ferroelectric Prop
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us scientific papers have been published concerning the spark plasma sintering (SPS) process.[1–3] SPS is a well-known technique for rapid densification of various ceramics at moderate temperatures. During the SPS process, a high electric-pulsed current is applied to provide high heating rate and the activation of powder VENKATA RAMANA MUDINEPALLI, Postdoctoral Research Associate, and W.C. LIN, Professor, are with the Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan. Contact e-mail: [email protected] FENG LENG, Research Scholar, is with the Department of Chemistry, University of Nevada, Las Vegas, Las Vegas, NV 89154. B.S. MURTY, Professor, is with the Department of Metallurgical and Materials Engineering, IIT Madras, Chennai, ndia. Manuscript submitted August 21, 2015. Article published online March 22, 2016 METALLURGICAL AND MATERIALS TRANSACTIONS A
particles is considered to be achieved at short time. Due to its high heating rate, high-energy activity, and short sintering time, grain coarsening can be inhibited and dense ceramics with higher performance can be obtained using SPS technique at lower sintering temperatures in comparison with conventional sintering (CS) techniques (pressure less sintering, (PLS), hot isostatic pressing (HIP), and hot pressing (HP)). A description of this method, its historical developments, and its related modifications is given in References 1 through 3. SPS technique has been extensively used to produce a wide range of materials including metals, ceramics, glass, and biomaterials.[4–7] The fast heating rate makes it unique for investigating bulk nano materials since the nanoscale structure may be retained due to the rapid sintering cycle. A fully dense part may be sintered in minutes using SPS instead of hours of using conventional methods like HP and HIP. The fast heating and forming process also ensure minimized grain growth; therefore, the unique properties of nano-scale materials may be retained. SPS is a relatively new sintering technique which takes only a few minutes to complete the uniform heating to high density at relatively low temperatures, while the other sintering techniques (conventional, hot pressing, and hot isostatic pressing) may take hours or even days for the same. Simultaneous application of temperature and pressure leads to high densification, and hence a dense compact at sintering temperatures lower by 473 K to 673 K (200 C to 400 C) than in other (solid-state conventional (SSC), hot press (HP), hot isostatic pressing (HIP), and microwave sintering) sintering is easily obtained. In SPS, since no coarsening and grain growth was allowed to occur, shorter sintering times and lower sintering temperatures required in the SPS process are advantageous in suppressing exaggerated grain growth. Hence, nano-structured ceramics or nano-composites can be easily prepared by SPS, and these nano-structured ceramics and composites exhibit excellent dielectric and ferroelectric properties.[8] Using SPS obtains a high density even at
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