LiIO3多型性相变的进一步研究

本文用差热分析、恒温热处理、X射线衍射等方法,对LiIO₃在常压的相变过程做了进一步的研究。对于LiIO₃的常压相变机制有了较为详尽的了解。并发现LiIO₃在高温可相对稳定存在三个相:β,η和δ,它们可分别自行熔化,其熔点相应为:432℃,421℃和416℃,从它们的热经历和存在的温度范围,表明其稳定性顺序为β>η>δ。在室温干燥空气中,与α相和β相共存的还有ζ相,ζ相升温放热转变为β相。在α相存在的温区里,ζ相经过长时间热处理并不转变为α相,同时,ζ相转变为β相的温度比α相高。与α→β的情况相同,β对ζ→β也有诱导作用。而且的ζ存在对α→β也有促进作用。θ相(θ₁与θ₂)与γ相一样,是相变过程的中间过渡相。 关键词：

FURTHER STUDIES ON THE PHASE TRANSITION OF LITHIUM IODATE (LiIO3) POLYMORPHISM

Further studies on the phase transition mechanism of LiIO₃ at normal pressure have been made by means of DTA, heat-treatment, and powder X-ray diffraction. There are three phases of LiIO₃, β,η,δ, existing relatively stably at high temperatures and they can directly melt respectively. Their melting points are as follows: phase β, 432℃; phase η, 421℃; phase δ, 416℃. The melting points, thermal processes and the exiting temperature ranges ail show that the order of their thermodynamical stability is: β>η>δ. In dry air and at room temperature, the phase ζ of LiIO₃, which changes to phase β when it is heated to 335℃ at 10℃/min, stands long periods of time without any change as well as phase α and β . In the existing temperature range of α -LiIO₃, phase ζ does not transform into phase α although it is heat-treated for a long time. The temperature of phase transition of ζ to β is higher than that of α to β. The existence of phase β in the phase ζ has a promotive effect on the phase transition of ζ to β just as the case of α to β. The existence of phase ζ in the phase α has also a promotive effect on α to β . The phase θ, like the phase γ. is also an intermediate metastable phase in the phase transition processes of LiIO₃.