A new radiative microfurnace has been developed for high‐temperature single‐crystal work on the four‐circle diffractometer. The microfurnace is fairly easy to construct and can be operated at temperatures up to 1270 K with a precision of ± 6 K. A calibrated shunt in the circuitry of the microfurnace is used to determine the microfurnace's resistance, current draw and power usage for any given temperature during a diffraction experiment. A procedure for mounting single crystals in a refractory cement that can be used as an internal calibrant of temperature is also described. The thermal expansion properties of periclase (MgO) have been reinvest