Development of High-Temperature Electronic Device by Microstructure Control of Composite Ceramics of Silicon Carbide

采用流态化-BEB化学气相沉积方法，在BCl3-NH3-H_2气相中将BN沉积在粒度为0.3um的碳化硅颗粒上，制备了SiCp-BN复合颗粒。复合粒子形成了大小约为50微米的球形团聚体。虽然BN倾向于在团聚体表面偏析，但通过控制制备条件，BN在团聚体内的分布是均匀的。通过TiCl4-CH4-H2气相沉积TiC，在团聚的碳化硅颗粒上沉积TiC，制备了TiC-TiC复合颗粒，并对复合颗粒进行了热压烧结。均匀分散的h-BN颗粒起到了松弛热应力的作用，使复合材料具有优异的抗热震性能。少量BN的加入降低了半导体碳化硅的电阻率，但由于BN是绝缘体，当BN含量较大时，其电阻率变大。碳化硅-碳化钛复合颗粒的烧结体具有较低的电阻率。由于TiC是金属导体，在团聚的复合颗粒上TiC似乎形成了网络结构，作为导电途径，TiC电极形成在半导体SiC上，TiC与碳化硅的稳定结合是通过在界面上分级组成来实现的。碳化硅与碳化钛之间的电连接为欧姆连接，表明梯度键合碳化钛电极可用于高温碳化硅电子器件。

SiC-BN composite particles were prepared by a fluidized-beb CVD method, in which BN was deposited on SiC particles (paticle size : 0.3mum) from BCl_3-NH_3-H_2 gas phase. The composite particles formed spherical agglomerates with sizes of about 50mum. Although BN tended to segregate on the agglomerate surface, the homogeneous distribution of BN inside the agglomerates was achieved by control of preparation conditions. SiC-TiC composite particles were also prepared by deposition of TiC from TiCl_4-CH_4-H_2 gas phase, in which TiC was deposited on agglomerated SiC particles.The sintered composites were fabricated by hot-pressing of the composite particles. The SiC-BN composite had an excellent thermal-shock resistance because of the relaxation of thermal stress by uniformly-dispersed h-BN particles. The electrical resistivity of semiconductive SiC was lowered by addition of small smount of BN,whereas the resistivity became large at large BN content, because BN is insulator. The sintered body of SiC-TiC composite particles exhibited the low resistivity. Since TiC is metallic conductor, TiC on the agglomerate composite particles seemed to form the network structure which worked as electrical conduction path.TiC electrode was formed on semiconductive SiC.The stable bonding of TiC to SiC was achieved by grading composition at the interface. The electrical connection between SiC and TiC was ohmic, indicating that the gradiently-bonded TiC electrode was useful for high-temperature SiC electronic device.