Influences of Hot-Pressing Conditions on the Optical Properties of Lanthanum Sulfide Ceramics

Abstract

The Ca‐doped γ‐La2S3 (γ‐La2S3:Ca) powders with various La/Ca ratios were prepared using the coprecipitation method. The γ‐La2S3:Ca powders with a ratio of La/Ca=5 was selected for sintering in order to study the effects of hot‐pressing temperature and time on the microstructure and optical properties of γ‐La2S3:Ca ceramics. The results showed that 1100°C for 1 h were the optimum hot‐press parameters, at which the maximum transmittance of γ‐La2S3:Ca ceramics up to 40% at 13 μm was obtained.

Processing of CaLa2S4 infrared transparent ceramics: A comparative study of HP and FAST/SPS techniques

“…This phase is a pseudo‐allotrope (low‐temperature phase) of γ‐La 2 S 3 , stabilized by residual oxygen (actually an oxysulfide of chemical formulation La 10 S 14 O). β‐La 2 S 3 forms in presence of oxygen concentration as low as 500 ppm and is consequently currently observed as impurity in CLS materials . Its contribution to the material optical properties is further addressed in Section 3.3 (B).…”

“…The first step is the synthesis of CLS precursors containing intimately mixed calcium and lanthanum ions, which could be either mixed oxides, coprecipitated carbonates, spray‐pyrolyzed mixed oxides ("evaporative decomposition of solutions" method), or alcoxides . These precursors are subsequently sulfurized in H 2 S or CS 2 atmosphere and converted into pure CLS powders. Sintering of the powders is thereafter carried out by different sintering techniques: Hot pressing (HP), natural sintering in sulfurizing atmosphere followed by HIP, or Field‐Assisted Sintering Technique (FAST also denominated as spark plasma sintering (SPS)) for which, to the best of our knowledge, only two references have been published very recently …”

“…[18][19][20][21][22] These precursors are subsequently sulfurized in H 2 S [12][13][14][15] or CS 2 22-24 atmosphere and converted into pure CLS powders. Sintering of the powders is thereafter carried out by different sintering techniques: Hot pressing (HP), 4,6,[24][25][26] natural sintering in sulfurizing atmosphere followed by HIP, 2,3,12,27 or Field-Assisted Sintering Technique (FAST also denominated as spark plasma sintering (SPS)) for which, to the best of our knowledge, only two references have been published very recently. 28,29 Reduction phenomena of CLS at high sintering temperatures, namely T ≥ 1000°C, are generally reported issues for sintered CLS ceramics.…”

Infrared-transparent glass ceramics: An exploratory study

“…By itself, GLS may not have sufficient LWIR transparency as the 1-mm thickness cut-off (50% transmission) is 10 μm, hence other components may be needed to stretch the LWIR cut-off wavelength, as GLS transmission may be limited by Ga 2 S 3 vibrations [32]. However, some crystalline phases containing elements in GLS are known to have longer LWIR transmission cut-offs of N 12 μm, including CaLa 2 S 4 , ZnGa 2 S 4 , and oxygen-free La 2 S 3 [28,[33][34][35]. The current study targets glasses with high enough concentrations of Zn and/or Ca such that these crystalline phases, in addition to Ga-La-S phases (of which many different crystalline phases exist [36]), might form.…”

Green hydrothermal synthesis and optical properties of γ-Gd2S3 nanoparticles

“…Rare earth sesquisulfides (Ln 2 S 3 ) are known to have three polymorphic forms; a, b, and c (Grzechnik et al 1999). Among these c-form is most studied for promising applications as optoelectronics (Krichevtsov et al 2001), piezoelectric transducers (Luguev et al 2000;Gadzhiev et al 2001;Grzechnik et al 2001;Qiu et al 1996;Witz et al 1996), and optical materials in IR transmission windows (Li et al 2011). For gadolinium sesquisulfides (Gd 2 S 3 ), a-phase is low-temperature phase, which transforms into c-phase with increase in temperature.…”