A current controlling device for an electrical circuit including a semiconductor element and electrodes in low electrical resistance contact therewith, wherein said semiconductor element has a threshold voltage value and a high electrical resistance to provide a blocking condition for substantially blocking current therethrough, wherein the high electrical resistance is substantially instantaneously decreased to a low resistance in response to a voltage above said threshold voltage value to provide a conducting condition for substantially conducting current therethrough, wherein the semiconductor element comprises high electrical resistance refractory powder particles substantially individually coated with a thin solid coating of substantially VO2, wherein the high electrical resistance refractory powder particles may comprise SnO2, SiO2, Al2O3, ZrO2 or TiO2 or the like, wherein the thin substantially VO2 coating on the particles is obtained from V2O5 and/or V2O3 in the formation thereof by several methods described herein, wherein the devices may be of the non-memory type or the memory type, and wherein the devices may have an intermediate or partial conducting condition.