Synthesis of novel alkaline-earth silicon nitrides and evaluation from the viewpoint of materials science

本文研究了碱土氮氧化硅(Ca-Si-O-N和Ba-Si-O-N系)的合成条件，主要从稀土离子的添加对其发光性能的影响方面考察了所得粉末的性能。本研究研究的氧氮化物材料为Ca3Si2O4N2、Ca2Si302N4和BaSi6ON8。本研究使用的原料为碳酸钙(CaCO3)、碳酸钡(BaCO3)、二氧化硅(SiO_2)、氮化硅(Si3N4)和稀土氧化物(=激活剂)；首先，以CaO、SiO_2和Si_3N_4为原料合成了Ca3Si_2O_4N_2(N/O比为0.5)，最佳合成条件(温度和时间)分别为1450℃和2 h。研究了(Ca_&lt；1-x&gt；Rex)_3Si_2O_4N_2(RE：稀土元素)的发光性质。在这些稀土掺杂化合物中，(Ca_&lt；1-x&gt；SMx)_3Si_2O_4N_2和(Ca_&lt；1-x&gt；Tbx)_3Si_2O_4N_2分别代表红色和绿色发射。另一方面，以CaO和Si_3N_4为原料，在1550℃下加热2 h，得到了单相的Ca_3Si_2O_2N_4(N/O比=2.0)。以BaCO_3、SiO_2和Si_3N_4为原料，经1750℃加热2 h，得到了单相BaSi6ON_8，其激发峰和发射峰分别位于363 nm和480 nm附近，(Ba&lt；1-x&gt；Ce_x)Si6ON_8的相对强度为0.95&gT；Ce&lt；0.05；)Si6O8与CaWO4作为标准物质的强度相比达到了0.82。(Ba&lt；1-x&gt；eux)Si6ON8的激发峰和发射峰分别位于300 nm和500 nm附近，为蓝绿色发射。(Ba&lt；0.96&gt；Eu&lt；0.04&gt；)Si6ON8的相对强度达到2.7。

The synthesis conditions of alkaline-earth silicon oxynitrides, Ca-Si-O-N and Ba-Si-O-N systems, have been investigated in this research; properties of the resulting powders were examined chiefly from the viewpoints of their luminescence characteristics due to the addition of rare-earth ions. The oxynitride materials examined in this research were Ca_3Si_2O_4N_2, Ca_2Si_30_2N_4 and BaSi_6ON_8. The starting materials used in this research were calcium carbonate (CaCO_3), barium carbonate (BaCO_3), silicon oxide (SiO_2), silicon nitride (Si_3N_4) and rare-earth oxide (= activator; Eu_2O_3, Yb_2O_3, CeO_2, Tb_4O_7 and Sm_2O_3).Firstly, the optimum conditions (temperature and time) for the synthesis of Ca_3Si_2O_4N_2 (N/O ratio = 0.5) prepared using CaO, SiO_2 and Si_3N_4 were found to be 1450℃ and 2 h, respectively. The luminescence properties of (Ca_<1-x>REx)_3Si_2O_4N_2 (RE: Rare earth element) were examined. Among these rare-earth doped compounds, (Ca_<1-x>Smx)_3Si_2O_4N_2 and (Ca_<1-x>Tbx) 3Si_2O_4N_2 indicated red and green emitting, respectively. On the other hand, the single phase of Ca_3Si_2O_2N_4(N/O ratio = 2.0) was obtained heating the starting materials (CaO and Si_3N_4) at 1550℃ for 2 h. The (Ca_<1-x>Eux)3Si_2O_2N_4 emitted the reddish orange light whose peak wavelength was shifted from 606 to 620 nm with increasing x value from 0.01 to 0.1.Furthermore, the single phase of BaSi_6ON_8 was obtained heating the starting materials (BaCO_3, SiO_2 and Si_3N_4) 1750℃ for 2 h. The excitation and emission peaks of (Ba_<1-x>Ce_x) Si_6ON_8 were observed at around 363 and 480 nm, respectively; the relative intensity of (Ba_<0.95>Ce_<0.05>) Si_6ON_8, compared to the intensity of CaWO_4 as a standard substance, attained 0.82. The excitation and emission peaks of (Ba_<1-x>Eux) Si_6ON_8 were found at around 300 and 500 nm, respectively, showing the blue-green emission. The relative intensity of (Ba_<0.96>Eu_<0.04>) Si_6ON_8 attained 2.7.