Atomic-scale assessment of the crystallization onset in silicon carbonitride

Abstract

Within the present study, atomic-scale electron microscopy investigation on the crystallization behavior of polysilylcarbodiimide-derived SiCN was performed. The as-prepared SiCN sample was found to be homogeneous and consisted of amorphous silicon nitride nano-domains dispersed within an amorphous, highly entangled graphene-like carbon matrix. Annealing of the sample at 1400 • C induced a slight increase of the ordering of the carbon phase. Additionally, the crystallization onset of the silicon nitride has been observed for the first time. In the sample annealed at 1400 • C small nano-clusters with average sizes of 0.8, 1.5 and 2.1 nm (consisting of 30, 180 and 570 atoms, respectively; corresponding to Si 12 N 18 , Si 72 N 108 and Si 228 N 342 ) were imaged and assigned to ␣-silicon nitride. The crystallization of the amorphous silicon nitride phase into ␣-Si 3 N 4 is thought to occur via diffusion of Si and N, which rely on the presence of large number of dangling bonds in the amorphous SiCN sample.

Synthesis and structural evolution of dual-boron-source-modified polysilazane derived SiBCN ceramics

“…4 These distinct advantages of SiBCN ceramics over traditional PDCs have inspired the development of SiBCN ceramics with much improved strengths and thermal stability with respect to oxidation and crystallization. 4 These distinct advantages of SiBCN ceramics over traditional PDCs have inspired the development of SiBCN ceramics with much improved strengths and thermal stability with respect to oxidation and crystallization.…”

Synthesis and high-temperature evolution of polysilylcarbodiimide-derived SiCN ceramic coatings

“…5 nm and thus larger than that of the clusters identified in [31]. This might rely on two aspects: (i) different crystallization behavior of the coatings as compared to bulk powder materials (though here the opposite trend would be expected, i.e., size of Si 3 N 4 precipitation in coatings should be smaller than that observed in bulk powders, as reported in [33] -the reason might be the extent of the free surface, much large in powders than in monolithic samples, which was shown promote the crystallization of Si 3 N 4 [33]); or (ii) the content of segregated carbon.…”

“…The formation of ␣-silicon nitride has been attributed to the diffusion of silicon atoms via dangling bonds in the amorphous silicon nitride network, which was observed by a recent atomic resolution STEM study on PV bulk ceramics [31], showing that the onset of crystallization of ␣-silicon nitride (clusters with average sizes of 0.8, 1.5 and 2.1 nm) occurs at 1400 • C.…”

“…5b show also only broad bumps, indicating as well an amorphous structure. Note that a recent detailed X-ray and atomic resolution TEM study on PV bulk material at 1100 • C and 1400 • C [31] is showing that this material consists of small nano clusters of ␣-silicon nitride with an onset crystallization temperature for silicon nitride of 1400 • C. Hence, the the broad bumps in Fig. 5b might be attributed to the 101, 110 and 210 reflections of ␣-Si 3 N 4 .…”

Mechanical Properties and Microstructural Characterization of Amorphous SiCxNy Thin Films After Annealing Beyond 1100°C

“…It has been shown that especially amorphous quaternary a‐SiBCN and ternary a‐SiCN can fulfill these demands . Both, the bulk (polymer to ceramic transformation from a single polymeric polyborosilazane) and the SiBCN thin films (DC magnetron sputtering from segmented B 4 C target with p ‐type Si stripes) were reported to possess an exceptional thermal stability even above 1500°C that was reported as an ultimate temperature for Si 3 N 4.…”