氟氢化钾固-固相变的变温红外光谱测定

氟氢化钾（KHF2）晶体随着温度的升高，在196℃发生可逆的固－固相变，晶型由低对称的西方晶系转变到高对称的立方晶系^[1]。由于氟氢化钾的固－固相变焓高，可应用于热能的贮存^[2]，它的高温相可用做高电导率的离子导体^[3]。氟氢化钾的应用强烈依赖于本身的晶体性，因此利用各种光谱、X－射线衍射、热分析等技术手段以及量子化学计算对两种晶相结构的研究已日趋完善^[4,5]。而对于其固－固相变升温过程中的动态测定还未见报道，这是由于一般的实验手段难以对升温过程进行原位跟踪所致。变温红外光变法具有简便、快速、实用等优点，因而成为研究相变的有力工具^[6]。本文采用变温红外光谱技术测定了氟氢化钾在不同温度下的红外光谱，发现当温度升高到固－固相变温度时，氟氢化钾的各个特征吸收峰的位置、强度及峰形均发生较大程度的变化，从而为验证氟氢化钾的固－固相变机理提供了依据。

IR Spectra at various Temperatures for Potassium Hydrogen Difluoride

The solid-solid phase transition of KHF2 was studied by infrared spectrometry at various temperatures and by differential scanning calorimetry(DSC) also. There are hydrogen bonds between the molecules which play a dominant role to the structure at low temperature state. In the temperature range closely corresponding to the solid-solid phase transition, the frequency of antisymmetric stretching(v3) shifted to a higher wavenumber, and the bending(v2) to lower wavenumber. The enthalpy and the temperature of solid-solid phase transition for KHF2 were measured by DSC method and the latter is consistent with the result of IR which could declare the mechanism of solid-solid phase transition of KHF2. With the breaking of hydrogen bonds between the molecules and the introduction of vibrational and rotational disorder KHF2 exhibited crystalline transition.