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Fabrication, thermal shock resistance, and dielectric property of α‐Si 3 N 4 ‐based ceramic coating on porous Si 3 N 4 ceramics
Author(s) -
Wang Chao,
Xia Yi,
Qiao Ruiqing,
Zhang Fan,
Chen Lijia,
Wang Zhanjie
Publication year - 2019
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/ijac.13214
Subject(s) - materials science , thermal shock , composite material , ceramic , dielectric , sialon , coating , porosity , fabrication , medicine , alternative medicine , optoelectronics , pathology
Abstract A dense α‐Si 3 N 4 ‐based ceramic protective coating was successfully prepared on porous Si 3 N 4 ceramics by a liquid infiltration and filling method. The coating composed of a primary α‐Si 3 N 4 phase and secondary O'‐Sialon, β‐Sialon, and Y–Si–Al–O–N glass phase. After thermal shock at Δ T = 1000°C for five times, cracks were produced, but the tip of crack stopped inside the coating; so the coated porous Si 3 N 4 ceramics still had a good waterproof ability and its water absorption was only 7%. During thermal shock, toughening mechanisms involving needle‐like O'‐Sialon particle bridging, crack deflection, and rough fracture, occurred within the cracks, contributing to thermal shock resistance of the coating. The dielectric constant of the coated porous Si 3 N 4 ceramics showed a slow increase trend with increasing temperature, and it reached the maximum value of 3.57 at 1100°C at the frequency of 11 GHz. The dielectric loss increased slowly as the temperature increased from room temperature to 900°C, but it started to increase evidently when the temperature was over 900°C.