Phase change memory materials in a dielectric-doped, antimony-rich GST family of materials which are antimony rich relative to GST-225, are described that have speed, retention and endurance characteristics suitable for storage class data storage A memory device includes an array of memory cells, where each memory cell includes a first electrode and a second electrode coupled to a memory element. The memory element comprises a body of phase change memory material that comprises a combination of Ge, Sb, and Te with a dielectric additive in amounts effective to provide a crystallization transition temperature greater than to 160° C., greater that 170° C. in some effective examples and greater than 190° C. in other effective examples. A controller is coupled to the array, and configured to execute set operations and reset operations for memory cells in the array.