Abstract: A heat treatment chamber (30) is provided comprising a treatment region containing a charge (5) of compound material comprising a plurality of n atomic species, each atomic species being associated with at least one gas species. The chamber (30) is placed in a furnace (7). The chamber has a gas permeable barrier, constituted by a plug (4) and wadding (6), which partially encloses the treatment region. The barrier serves as an effusive hole to inhibit, but not prevent, gas vapour release, thereby to elevate the gas vapour pressure in the treatment region. Application of inert gas through a valve (8) is also used to increase background pressure in the treatment region during heat treatment. The elevated gas pressures present in the treatment region during treatment are measurable in an absorption cell (3) adjacent to the treatment region. It is thus possible to monitor the gas pressures during heat treatment and thereby stop the heat treatment once a desired charge stoichiometry is achieved.

Abstract: A heat treatment chamber (30) is provided comprising a treatment region containing a charge (5) of compound material comprising a plurality of n atomic species, each atomic species being associated with at least one gas species. The chamber (30) is placed in a furnace (7). The chamber has a gas permeable barrier, constituted by a plug (4) and wadding (6), which partially encloses the treatment region. The barrier serves as an effusive hole to inhibit, but not prevent, gas vapour release, thereby to elevate the gas vapour pressure in the treatment region. Application of inert gas through a valve (8) is also used to increase background pressure in the treatment region during heat treatment. The elevated gas pressures present in the treatment region during treatment are measurable in an absorption cell (3) adjacent to the treatment region. It is thus possible to monitor the gas pressures during heat treatment and thereby stop the heat treatment once a desired charge stoichiometry is achieved.