Method for controlling flux pressure during a sintering process

摘要

In a sintering process, the vapour pressure of the flux used is maintained substantially constant so that the flux concentration does not decrease during the process and affect the sintering. Preferred materials are photo-conductors such as CdSe and CdS or a solid solution of both using CdCr2, CdBr2 or CdI2 as fluxes. Numerous examples are given utilizing these materials, the sintering treatments involving heating to temperatures between 522 DEG and 600 DEG C. for 5-20 minutes in an atmosphere of 0.2 to 1.7% O and the rest N and the mixtures having between 5 and 20 mol. per cent flux; grain sizes between 4 and 15 m result. Copper may be added as an impurity. The vapour pressure is maintained either by using a small volume container or by providing an auxiliary source for vapour consisting merely of the flux material or alternatively using a second supply of the mixture which is being sintered. This auxiliary source may be covered with a layer of Al2O3 which acts as a molecular sieve to govern the rate of evaporation. Fig. 3 shows a suitable small volume inner container 10 which is closed by a substrate 11 carrying on its inner surface the material to be sintered. The container is carried on an endless chain 6 in the heating apparatus shown in Fig. 2 which comprises a glove box 1 and furnace 12. Means are provided for circulating and controlling the atmosphere. When only small quantities of flux are used which are insufficient to fill the container with vapour without affecting the residue, secondary sources of flux vapour are provided in the bottom of the container 10.