添加ZrO_2或Y_2O_3对氧化镁高温真空稳定性的影响

Effect of ZrO_2 or Y_2O_3 on high temperature vacuum stability of magnesia

为提高氧化镁在高温真空环境下的稳定性,在粒度≤0.074 mm、w(Mg O)=98.70%的轻烧氧化镁粉中分别外加质量分数为0、0.5%、1%和2%的Zr O2或Y2O3后,混合、成型的试样经1 750℃保温6 h煅烧。将煅烧后试样在真空度为1.5×10-2Pa、于1 600℃保温1 h的条件下进行真空稳定性试验,然后对试样的质量损失、物相组成进行分析,并进行晶体学计算。结果表明:添加Zr O2或Y2O3可引起氧化镁的晶格畸变,Zr4+、Y3+部分取代Mg O晶格中Mg2+位置,形成晶格畸变,同时产生阳离子空位,对周围原子起到束缚作用,降低了原子振动频率,从而减少逸散原子的数量,提高了氧化镁在高温真空条件下的稳定性。

In order to improve the stability of magnesia in high temperature vacuum environment, specimens were prepared by extra-adding different amounts of zirconia or yttrium oxide （0,0.5%, 1%, and 2%, by mass） into caustic-calcined magnesia with 98.70 mass% MgO and ≤0. 074 mm of particle size,then mixing,shaping and calcining at 1750 ℃ for 6 h. Then the vacuum stability of the calcined specimens was tested under 1.5× 10^-2 Pa of vacuum degree at 1 600 ℃ for 1 h. The mass loss, phase composition and crystallographic calculation of specimens were investigated. The results indicate that adding zirconia or yttrium oxide can cause lattice distortion in magnesia： Zr^4＋ and y^3＋ partly substitute Mg^2＋ in MgO crystal structure which results in lattice distortion and produces cation vacancies, bonding the surrounding atoms and reducing the vibration frequency of atoms ;thus the released atoms decrease so the vacuum stability of magnesia at high temperatures is enhanced.