Crystal structure and proton conductivity of a new Cs3(H2PO4)(HPO4)·2H2O phase in the caesium di- and monohydrogen orthophosphate system.
Crystal structure and proton conductivity of a new Cs3(H2PO4)(HPO4)·2H2O phase in the caesium di- and monohydrogen orthophosphate system.
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正磷酸二氢和一氢铯体系中新 Cs3(H2PO4)(HPO4)·2H2O 相的晶体结构和质子电导率。
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发表时间：
2017
期刊：
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通讯作者：
E. Boldyreva
中科院分区：
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作者：
V. Ponomareva;I. Bagryantseva;B. Zakharov;N. Bulina;G. Lavrova;E. Boldyreva
MxHy(AO4)z酸盐（M = Cs, Rb， K, Na, Li, NH4; A = S, Se, As， P）表现出铁电性质。固体酸具有较低的电导率值，它们的热性质和质子电导率引起了人们的兴趣。研究了正磷酸二氢铯和二水正磷酸一氢铯Cs3(H1.5PO4)2·2H2O的晶体结构。该化合物在Pbca空间基团中结晶，形成了连接磷酸四面体的强氢键结构，与红外光谱吻合良好。在348 ~ 433 K时，Cs3(H1.5PO4)2·2H2O发生脱水，损失两个水分子。无水Cs3(H1.5PO4)2在548 K时稳定，然后完全转化为焦磷酸铯（Cs4P2O7）和CsPO3。无水Cs3(H1.5PO4)2在单斜C2空间群中结晶，晶胞参数a = 11.1693 (4), b = 6.4682 (2), c = 7.7442 (3) Å， β = 71.822(2)°。测量了两种化合物的电导率。与晶体水合物Cs3(H1.5PO4)2·2H2O相比，在373-493 K下，脱水形式的电导率值相当低，为~ 6 × 10-6-10-8 S cm-1，活化能为0.91 eV。
The MxHy(AO4)z acid salts (M = Cs, Rb, K, Na, Li, NH4; A = S, Se, As, P) exhibit ferroelectric properties. The solid acids have low conductivity values and are of interest with regard to their thermal properties and proton conductivity. The crystal structure of caesium dihydrogen orthophosphate monohydrogen orthophosphate dihydrate, Cs3(H1.5PO4)2·2H2O, has been solved. The compound crystallizes in the space group Pbca and forms a structure with strong hydrogen bonds connecting phosphate tetrahedra that agrees well with the IR spectra. The dehydration of Cs3(H1.5PO4)2·2H2O with the loss of two water molecules occurs at 348-433 K. Anhydrous Cs3(H1.5PO4)2 is stable up to 548 K and is then converted completely into caesium pyrophosphate (Cs4P2O7) and CsPO3. Anhydrous Cs3(H1.5PO4)2 crystallizes in the monoclinic C2 space group, with the unit-cell parameters a = 11.1693 (4), b = 6.4682 (2), c = 7.7442 (3) Å and β = 71.822 (2)°. The conductivities of both compounds have been measured. In contrast to crystal hydrate Cs3(H1.5PO4)2·2H2O, the dehydrated form has rather low conductivity values of ∼6 × 10-6-10-8 S cm-1 at 373-493 K, with an activation energy of 0.91 eV.