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Spark‐Plasma‐Sintering Condition Optimization for Producing Transparent MgAl 2 O 4 Spinel Polycrystal
Author(s) -
Morita Koji,
Kim ByungNam,
Yoshida Hidehiro,
Hiraga Keijiro
Publication year - 2009
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2009.03074.x
Subject(s) - spinel , materials science , spark plasma sintering , sintering , crystallite , porosity , coalescence (physics) , grain size , transparent ceramics , grain growth , metallurgy , analytical chemistry (journal) , composite material , mineralogy , chemistry , physics , chromatography , astrobiology
By controlling the heating rate at <10°C/min during spark‐plasma‐sintering (SPS) processing, transparent polycrystalline spinel with an in‐line transmission of 50% and 70% in the visible‐ and infrared‐wavelengths, respectively, can be successfully fabricated for only a 20‐min soak at 1300°C. The high transmission can be attained by reducing the residual porosity and pore size, which was achieved by the low‐heating rate. At high heating rates, many closed pores are formed due to the high densification rate during the heating process and remain as large pores around grain junctions. At temperatures >1300°C, the coalescence of the residual pores and the precipitation of second phases, which are caused by rapid grain growth, degrade the transparency. The present study demonstrates that although the high heating rates have been regarded as a primary advantage for the SPS processing, the low heating rate is highly effective in attaining a high transparency in the spinel even at low temperatures and for short sintering times.