High purity Al2O3 ceramic:Metallizing strategy, microstructure and sealing properties

ABSTRACT A high purity Al2O3 ceramic (HPAOC) metallizing strategy was developed via gradient coating process of metallizing pastes with different ratios of Mo to manganese glass (MnG) contents, to improve the wettability and reactivity of metallized layer (ML) to the ceramic substrate and the secondary metallizing layer or sealed metals. Self-made HPAOC samples firstly coated by a layer of metallizing paste with a lower proportion of Mo:MnG and superposed a layer of metallizing paste with a higher proportion of Mo:MnG were fired at 1450°C in hydrogen atmosphere. The crystal phase structure, microstructure and element distribution of the metallized samples wer characterized by XRD, SEM and EDS. The results of sealing properties show that the tensile sealing strength of as high as 121MPa and the He leakage rate of as low as 4.2 × 10−11 Pa.m3/s can be obtained of the sealed joints of the as-metallized HPAOC and Kovar.