A series of M3PS4 (M = Ag, Cu and Ag/Cu) thiophosphates with diamond-like structures exhibiting large second harmonic generation responses and moderate ion conductivities.

Abstract

A series of thiophosphates with similar diamond-like structures, M3PS4 (M = Ag, Cu and Ag/Cu), were successfully synthesized. Among them, Ag3PS4 and Ag1.5Cu1.5PS4 satisfy the phase-matching condition and display excellent second harmonic generation (SHG) responses about 1.3 and 0.8 times that of benchmark AgGaS2. First-principles and dipole moment calculations indicate that their SHG effects originate from the combined action between MS4 and PS4 tetrahedra. Moreover, they also exhibit moderate ion conductivities (order of 10-7 to 10-5 S cm-1) between 10 and 80 °C and relatively small activation energies (Ea = 0.28-0.34 eV).