## 2 Materials and Methods  
The raw materials used in this study are listed in Table 1. All the information of raw materials was provided by their suppliers. The slurry designations and corresponding compositions are outlined in Table 2. The yttria-alumina (Y\({}_{2}\)O\({}_{3}\)-Al\({}_{2}\)O\({}_{3}\)) system is the most widely applied sintering aid system for the facilitation of liquid phase sintering in Si\({}_{3}\)N\({}_{4}\) at low temperature (<1800 \({}^{\circ}\)C) to achieve densification [38; 39]. The amounts of sintering additives in the Si\({}_{3}\)N\({}_{4}\) and (Si\({}_{3}\)N\({}_{4}\) + Si) slurries were calculated in order to yield a fully nitridded green body with a nominal composition of Si\({}_{3}\)N\({}_{4}\): Y\({}_{2}\)O\({}_{3}\): Al\({}_{2}\)O\({}_{3}\) = 93: 5: 2 at mass ratio. BYK-103 was used as the dispersant to stabilize ceramic particle, with a weight content (relative to the total powder mass) of 3 wt.%. The acrylate monomers (HDDA and NPG2 PODA) and photoinitiator (TPO-L) all belonged to free radical polymerization system. \begin{table}
\begin{tabular}{c c c c c} \hline
**Material** & **State** & **Usage** & **Description** & **Supplier** \\ \hline Si\({}_{\text{N}}\)N\({}_{\text{1}}\) powder & Solid & Filler & D\({}_{0}\) = 0.5 μm, gray color & Qinhuangdao Eno Material Co., Ltd. \\ Si\({}_{\text{N}}\)N\({}_{\text{1}}\) powder & Solid & Filler & D\({}_{0}\) = 0.5 μm, gray color & DERA Co., Ltd. \\ Si\({}_{\text{N}}\)N\({}_{\text{2}}\) powder & Solid & Filler & D\({}_{0}\) = 0.65 μm, gray color & Ube Industries Co., Ltd. \\ Si powder & Solid & Filler & D\({}_{0}\) = 5 μm, black color & Xuzhou Lingrum Silicon Industry Co., Ltd. \\ Y\({}_{\text{2}}\)O\({}_{\text{1}}\) powder & Solid & Sintering additive & D\({}_{0}\) = 0.5 μm, white color & Shanghai yvoteal metal material Co\({}_{\text{1}}\), Ltd. \\ Al\({}_{\text{2}}\)O\({}_{\text{1}}\) powder & Solid & Sintering additive & D\({}_{0}\) = 0.4 μm, white color & Alteo \\ ZrO\({}_{\text{2}}\) powder & Solid & Filler & D\({}_{0}\) = 0.6 μm, white color & Toson Corp. \\ HDDA & Liquid & Binder & Di-functional acrylate, M\({}_{\text{u}}\)-\(\underline{328}\) pinned, viscosity is 5-10 mPa\({}_{\text{8}}\) & DSM \\ NPC2 PODA & Liquid & Binder & D-functional acrylate, M\({}_{\text{u}}\)-\(\underline{328}\) pinned, viscosity is 10-20 mPa\({}_{\text{8}}\) & DSM \\ PIG-400 & Liquid & Diluent & Polyethylene glycol & Aladdin \\ TTO-L & Liquid & Photoininator & ethyl(24,6-trimethylphenyloxy)/phenyl phosphinate & ICM \\ BYK-103 & Liquid & Dispersant & solution of a copolymer with filler affinic groups & BYK Chemie GmbH \\ \hline \end{tabular}
\end{table} 
Table 1: Data of the raw materials. In this work, the slurries with defined composition were well blended by roll milling. The stereolithography process was conducted by using a commercial Digital Light Processing (DLP) additive manufacturing equipment (Admaflex 130, ADMATEC, The Netherlands), at a humidity of 42\(\sim\)44% and a temperature of 26\(\sim\)28 \({}^{\circ}\)C. The transportation of slurry was based on the principle of tape-casting. In this paper, the transport speed was set at 15,000 \(\upmu\)m/s and the gap between blade and transparent foil was controlled at 150 \(\upmu\)m (corresponding to a shear rate of 100 s\({}^{-1}\)). The printing process was illustrated in Figure 1. Other details involving equipment structure and working principle can be found in our previous work [16]. To better understand the flowability of these suspensions, the rheological properties of the fresh Si\({}_{3}\)N\({}_{4}\) slurries were analyzed using a rotational rheometer (MCR 301, [PERSON], Austria). Unless otherwise stated, all the rheological measurements were conducted at 25 \({}^{\circ}\)C. The light absorbance of ceramic powders was tested by using an Ultraviolet-visible spectrophotometer (UV-3600, Shimadzu, Japan).