Preparation And Properties Of Rare Earth Sesquisulfides

Rare earth sesquisulfides can be utilized as the paint,thermoelectric materials, and luminescent materials, for the unique features in the fields of light, magnetism, electricity. In view of this, the problems in industrial applications are investigated in this work,such as:High temperature phase y-La2S3 is difficult to be formed at lower temperatures; The morphology can not be well controlled through industrial preparation methods; The luminous mechanism of rare earth ions is not clear. The major works are shown as follows:1. Oxalate precipitation method is used to product lanthanum oxalate precursors doped with different concentration of rare earth Eu ions. Then Rare earth sulfides can be prepered by the vulcanization of CS2. The composition of target products is analyzed by energy spectrum, and the structure of the products is determined by X-ray diffraction. During the sulfurizing reaction process, the prior formed cubic Eu3S4 crystals plays a role as y-La2S3 seeds, which provide nuclei for the y-La2S3 phase. The y-La2S3 transformation temperature is lowered to a remarkable extent by the joint contribution of low transformation enthalpy and induced multiple nuclei due to the Eu3S4 nuclei.2. Nano-precursors are prepared by homogeneous precipitation.Then Rare earth sulfides can be prepered by the vulcanization of CS2. When the concentration of urea against rare earth ions is 100 and 50 separate as the aging time and temperature is fixed, the dimension of final products is 200nm and 400nm relatively. To study the effect of the morphology affected by the temperature, this paper chooses reaction temperature 700℃and 800℃. Finally, the different effects of air flow intensity on the morphology are studied. When the concentration ratio of urea against rare earth ions is 50, curing temperature is 700℃, the air flow rate of is 50ml/min, the monodisperse lanthanum sulfide with spherical morphology is prepared.3. La2S3:Tb is prepared by homogeneous precipitation method coupled with carbon disulfide vulcanization. And contrast with La2O2S:Tb, the luminescence mechanism of rare earth sulfides is studied.