Abstract: A frit-sealed x-ray tube includes a glass bulb that supports metallic parts including an anode with a target and a beryllium window. Joint materials are provided of metal with thermal expansion coefficients that approximate the thermal expansion coefficient of the glass bulb. Frit materials having compositions of primarily zinc oxide and lead oxide are used and also have a thermal expansion coefficient that approximates the thermal expansion coefficients of the glass bulb and the joint materials. The frit materials allow a heat resistant and vacuum resistant welding between the glass bulb and the joint materials.