Effect of Y doping on high-pressure behavior of Ag2S nanocrystals

The effect of the dopant Y on high-pressure-induced polymorph transformation was investigated in Ag2S nanocrystals. A polymorph transformation from monoclinic P2(1)/n phase I (where Ag1 and Ag2 atoms both participated in four-fold-coordinated tetrahedra) to orthorhombic P2(1)2(1)2(1) phase II (where Ag2 participated in four-fold-coordinated distorted tetrahedra but Ag1 in five-fold-coordinated pyramids) and then to another monoclinic P2(1)/n phase III (where Ag1 was still in the five-coordination pyramid-like structure but Ag-2 showed a coordination number of five to form trigonal bipyramids) was observed under increasing high pressure at room temperature. The initial monoclinic phase was fully recovered after decompression. Compared with the two transition pressure values of the pure Ag2S sample, those of the Y-doped sample were found to be lower, revealing the significant influence of even a low Y dopant concentration on the compressibility of Ag2S. The smaller bulk modulus and larger volume collapse of the Ag2S: Y sample further suggested it to be more compressible.