AEAg7(PS4)3 (AE = Ba, Sr): The homovalent substitution of lead by alkaline earth metals achieves the separation of the two phases and enlarges the band gap.

Two alkaline earth metal-containing thiophosphate compounds, BaAg 7 (PS 4) 3 and SrAg 7 (PS 4) 3 , were synthesized via the homovalent substitution of Pb2+ in PbAg 7 (PS 4) 3 by Ba2+ and Sr2+, respectively. The space group of BaAg 7 (PS 4) 3 (P 2 1 / c) and SrAg 7 (PS 4) 3 (P 6 3 / m) is the same as the low- and high-temperature phases of PbAg 7 (PS 4) 3 , respectively. The two compounds exhibit structural similarity and possess three-dimensional honeycomb-shaped architectures. These honeycomb structures are arranged in a layered fashion via hexagonal rings, which arise from the sharing of edges or vertices between [AgS 4 ] and [PS 4 ] tetrahedral, accommodating discrete entities of Ba2+ and Sr2+ cations. BaAg 7 (PS 4) 3 melts congruently with a melting point of 760 °C and a solidification point of 675 °C, while the melting behaviour of SrAg 7 (PS 4) 3 was incongruently and thermally stable up to 689 °C under vacuum of 1 × 10−3 Pa. Moreover, the band gaps of BaAg 7 (PS 4) 3 (2.69 eV) and SrAg 7 (PS 4) 3 (2.85 eV) have a significant enlargement compared to PbAg 7 (PS 4) 3 (2.09 eV). The combination of d10 cation Ag+ with second-order Jahn-Teller distortion and alkaline earth metals cation enriches the system of new metal thiophosphates and provides ideas for exploring other functional materials. Two new phosphorothioates, BaAg 7 (PS 4) 3 and SrAg 7 (PS 4) 3 , were prepared by the homovalent substitution of PbAg 7 (PS 4) 3 , and their space groups corresponded to the low-temperature and high-temperature phases of PbAg 7 (PS 4) 3 , respectively. [Display omitted] • Two new thiophosphates BaAg 7 (PS 4) 3 and SrAg 7 (PS 4) 3 were prepared by the homovalent substitution of PbAg 7 (PS 4) 3. • The space group of BaAg 7 (PS 4) 3 and SrAg 7 (PS 4) 3 corresponds to the low- and high-temperature phases of PbAg 7 (PS 4) 3. • The band gaps of BaAg 7 (PS 4) 3 (2.69 eV) and SrAg 7 (PS 4) 3 (2.85 eV) are compared with PbAg 7 (PS 4) 3 (2.09 eV). [ABSTRACT FROM AUTHOR]