Infrared Transmission Curves of Pb0.1 Ca0.9La2S4 Pellets Densified by Pressureless Sintering

Highly sinterable submicron Pb_0.l Ca_0.9La₂S₄(PCLS) powders were prepared by sulfidizing calcium and lanthanum alkoxides al 500°C under CS, atmosphere for 8 hours and then in pure H₂S atmosphere at 600-800°C for 8 hours. After sintering the pellets were used as infrared transmitting window material of 8-14 μm wavelength. The CdS was added from 3 to 7 wt.% lo improve the sinterability by forming liquid phase during sintering. For sulfidization of lanthanum alkoxide, sulfide powder with LaS₂ phase was formed at 500°C, and a pure Th3P4 phase formed follow by 700°C heat treatment. A powder with β-La₂S₃phase formed at 800°C, and a pure Th₃ P₄phase formed follow by 900°C heat treatment. The powder with β-La₂S₃ phase was sintered to full density at 1350°C by adding 3 wt.% CdS. The PCLS powder with Th3P4 phase sintered to full density at 1400°C by also adding 3 wt.% CdS. The pellet exhibited 45% transmittanceat 13 μm when sintered from the powder with p-La₂S₃phase. The transmittance at 2.5 μm for the pellet sintered from the PCLS powder with Th₃P₄ type structure was 3 times higher than that from the p-La₂S₃ powder.