## 3 Results and Discussion  
### Sintering Behavior  
The XRD patterns and morphology of the received powders were presented in Figure 1. Compared with the standard XRD patterns of CaSiO\({}_{3}\) (beta phase, JCPDS 84-0654) and ZnO (JCPDS 36-1451), it was clear that all of the primary strong and sharp diffraction peaks of the CaSiO\({}_{3}\) (Figure 1a) and ZnO (Figure 1b) powders could be indexed, respectively. The B\({}_{2}\)O\({}_{3}\) powder was amorphous which was identified completely by the B\({}_{2}\)O\({}_{3}\) diffraction code of JCPDS 06-0297 (Figure 1c). CaSiO\({}_{3}\) and B\({}_{2}\)O\({}_{3}\) powders had a particle-like morphology with an average particle size of 1.5 \(\upmu\)m and 40 \(\upmu\)m respectively, and ZnO had a whisker-like shape. The rhomboid scaffolds had a 75-degree acute angle and dimensions of 14 \(\times\) 14 \(\times\) 5 mm\({}^{3}\) (length \(\times\) width \(\times\) height) (Figure 1d). Other researchers reported that scaffolds required a pore size greater than 300 \(\upmu\)m to promote vascularisation and bone ingrowth for bone repair [29; 30]. The struts and pores of the scaffolds were around 2 mm and 1 mm, respectively. Moreover, the external and internal architectures of the scaffolds were well controlled.  
The diffraction peaks of all scaffolds were similar and no new phases were detected (Figure 2). Compared with the standard patterns of beta CaSiO\({}_{3}\) and alpha CaSiO\({}_{3}\) (JCPDS 74-0874), the two phases existed in all patterns, which represented a certain extent of phase transformation from beta phase to alpha phase during the sintering process. These results indicated that B\({}_{2}\)O\({}_{3}\)-ZnO liquid phase did not react with CaSiO\({}_{3}\).  
Microstructures of the thermally etched surface at 1050 \({}^{\circ}\)C in air were displayed in Figure 3. The group CS, CS-A, CS-B, CS-C and CS-D represented the CaSiO\({}_{3}\) scaffolds without B\({}_{2}\)O\({}_{3}\)-ZnO, CaSiO\({}_{3}\) with 47% B\({}_{2}\)O\({}_{3}\)-53% ZnO, CaSiO\({}_{3}\) with 40% B\({}_{2}\)O\({}_{3}\)-60% ZnO, CaSiO\({}_{3}\) with 35% B\({}_{2}\)O\({}_{3}\)-65% ZnO and CaSiO\({}_{3}\) with 25% B\({}_{2}\)O\({}_{3}\)-75% ZnO, respectively. The grains were arranged loosely in group CS and there were some holes, which demonstrated that densification was not sufficient for the scaffolds  
Figure 1: X-ray diffraction (XRD) patterns and microstructures of (**a**) CaSiO\({}_{3}\) powder; (**b**) ZnO powder and (**c**) B\({}_{2}\)O\({}_{3}\) powder and (**d**) a CaSiO\({}_{3}\) scaffold (enlarged image at top right corner).  
without liquid phase (Figure 3a). The other four groups revealed a highly dense structure, which indicated that the liquid phase enhanced sinterability and densification. Group CS-A (Figure 3b) possessed a relatively uniform particle size. In groups CS-B (Figure 3c) and CS-C (Figure 3d), several elongated grains appeared because the CaSiO\({}_{3}\) grains grew rapidly along the non-uniform grain morphology. Meanwhile, the space between grains of group CS-C decreased compared with group CS-B. The chemical component of group CS-C was detected by elemental maps (Figure 3f-h). The results revealed that almost all of the Zn presented in the grain boundaries (Figure 3h). Abnormal grain growth appeared at group CS-D (Figure 3e).