The structure of Zr5Si4 was solved in P41212 space group which is enantiomeric with P43212, the space group of the average model of phase B, and a direct supergroup for P21. Figure shows the Zr5Si4 structure in comparison with the Ba-Y-Si network in the structure of Ba3Y2[Si2O7]2. The structure of the silicide features pairs of silicon atoms with a rather short Zr-Zr distance of 2.471 Å that resemble the distribution of disilicate groups in Ba3Y2[Si2O7]2. The ratio of heavy atoms to silicon also remains the same: 5 Zr : 4 Si and (3Ba + 2Y): 4 Si. The unit cell of a disilicate (9.04 × 9.04 × 16.47 Å 3 ) has expanded by 100% in comparison to those of the zirconium silicide (7.12 × 7.12 × 13.0 Å 3 ) to accommodate oxygen atoms. An unknown amorphous content prevented further physical property investigation of phase B. We can assume that the range of applications for phase B could be very similar to phase A and other silicates. One might expect better ionic conductivity due to a high degree of disorder and respectively lower thermal conductivity (vide infra). At the same time, the lack of rigidity and amorphization after prolonged heat treatment makes it unsuitable for doping in the context of luminescence studies. Synthesis of this structure type in a chemical space where there is less competition with disorder will enable further exploration of these possibilities.