Disclosed herein are radio frequency (RF) cavities and systems including such RF cavities. The RF cavities are characterized as having an insert with at least one sidewall coated with a material to prevent charge build up without affecting RF input power and that is heat and vacuum compatible. One example RF cavity 206 includes a dielectric insert 222, the dielectric insert having an opening extending from one side of the dielectric insert to another to form a via 230, and a coating layer disposed on an inner surface of the dielectric insert, the inner surface facing the via 230, wherein the coating layer has a thickness and a resistivity, the thickness less than a thickness threshold, and the resistivity greater than a resistivity threshold, wherein the thickness and resistivity thresholds are based partly on operating parameters of the RF cavity.