A better alternative for glass is quartz glass, which you can apply up to approx. 1100°C in air. At 600°C, you can also use stainless steels if your product does not cause corrosion of steel.
You can not properly seal the lid at this temperature, but you can realize the sealing outside the oven:
@vadim verlotski, i need to heat in the absence of air and i want to observe the changes as the temperature rises. so, i want to avoid ss or metal. i thought about using a container which can withstand such temperature and sealing it off with ceramics. i have to avoid air as much as possible.