*3.1. Phase Structures*

The XRD patterns of the pure CBT and CBT-*x*Gd/0.2Mn ceramics were performed as shown in Figure 1. It indicated the X-ray diffraction peak of the Pure CBT and the CBT-*x*Gd/0.2Mn ceramics were consistent with the JCPDS card No.52-1640. Furthermore, all samples were orthorhombic in structure and A21am in space group. There is no other phase from the XRD pattern results of the CBT-*x*Gd/0.2Mn ceramics, which indicated codoping Gd/Mn formed a complete solid solution with CaBi4Ti4O15; the strongest diffraction peak of the CBT-*x*Gd/0.2Mn ceramics was (1 1 9) peak, which was consistent with the strongest diffraction peak (1 1 2m+1) of BLSF ceramics [24,25]. Compared with the pure CBT, CBT-*x*Gd/0.2Mn ceramics showed a smaller cell volume (*V*) from the Table 1 of the cell paraments, and the results revealed Gd/Mn could reduce the grain size, which was valuable to increase the piezoelectricity. The amount of Gd/Mn co-doping increased had little change to the orthorhombic distortion (*a*/*b*).

**Figure 1.** Rietveld analysis of XRD patterns of the CBT−*x*Gd/0.2Mn ceramics measured at room temperature.

**Table 1.** Lattice parameters of the CBT-*x*Gd/0.2Mn ceramics.

