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Ultra‐rapid microwave sintering of pure and Y 2 O 3 ‐doped MgAl 2 O 4
Author(s) -
Bykov Yury V.,
Egorov Sergei V.,
Eremeev Anatolii G.,
Kholoptsev Vladislav V.,
Plotnikov Ivan V.,
Rybakov Kirill I.,
Sorokin Andrei A.,
Balabanov Stanislav S.,
Belyaev Alexander V.
Publication year - 2019
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/jace.15788
Subject(s) - sintering , materials science , microwave , isothermal process , spinel , analytical chemistry (journal) , gyrotron , doping , power density , relative density , flash (photography) , mineralogy , metallurgy , thermodynamics , power (physics) , chemistry , optoelectronics , optics , physics , chromatography , quantum mechanics
MgAl 2 O 4 samples were microwave sintered to near‐full density in rapid processes with heating rates on the order of 100°C/min and zero isothermal hold. The experiments were carried out using a gyrotron system for microwave processing of materials operating at a frequency of 24 GHz with a maximum power of 6 kW . In the regimes with a preset heating rate sustained by the automatically regulated microwave power, the maximum achieved density was about 95% of the theoretical value in pristine MgAl 2 O 4 samples (maximum sintering temperature 1650°C) and about 97% in 1 wt.% Y 2 O 3 ‐doped samples (1700°C). In the regimes with a fixed microwave power (about 3.5 kW), translucent spinel samples with a relative density above 99% were obtained at 1700°C. The duration of the high‐temperature stage of sintering was 1.5‐10 minutes. The suggested mechanism responsible for the enhanced densification involves development of a thermal instability and formation of transient liquid phases at grain boundaries. The estimated specific absorbed power in the samples during the high‐temperature stage of ultra‐rapid microwave sintering was 27‐80 W/cm 3 , similar to the values observed in dc field‐assisted flash sintering experiments.