Which ceramic-like material is used in halogen MR16, GU5.3 and so on bulbs?
Actually, aside from heat resistance, a primary qualification is that the adhesive cement thermal expansion coefficient match that of the quartz (or glass or alumina) envelope over the temperature range of storage and operation, to avoid cracking the envelope (the metal fixture is more flexible and &quot;forgiving&quot;).
There are a number of cements in use, such as, &quot;aluminum phosphate refractory cement... a mixture of aluminum phosphate... phosphoric acid [and] alumina&quot;. Glassbond sells a variety of adhesives, such as a phenolic/melamine adhesive for glass lamps with operating temperature below 300°C. Sauereisen has a long history making high-temperature adhesives, including those of silicate and of magnesium oxysulfate composition. One could try making these cements at home or in the lab, though they're readily available commercially. You could experiment with refractory furnace cement, though it likely would have a different coefficient of expansion, cracking the envelope.
BTW, I remember, in school, attaching thermocouples to incandescent lamps with a variety of cements... and watching the glass envelope form small star-shaped cracks at each joint, for many of those adhesives, as the lamp warmed. Sorry, but I don't remember which formulations actually succeeded past a few on/off cycles.