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首页> 外文期刊>Acta Crystallographica, Section B. Structural science, crystal engineering and materials >Phase transitions in ferroelectric 4-aminopyridinium tetrachloroantimonate(III) - revisited
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Phase transitions in ferroelectric 4-aminopyridinium tetrachloroantimonate(III) - revisited

机译：铁电4-氨基吡啶四氯丙酸酯（III）的相转变 - 重访

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摘要

New X-ray diffraction studies on the crystal structure of ferroelectric [4-NH_2C_5H_4NH][SbCl_4] indicate that in the broad temperature range from 240 to 304 K covering the three intermediate phases, the crystal structure is modulated. Phase II is incommensurately modulated with modulation vector q = βb~*, β varying from 0.60 to 0.66 and monoclinic C2/c(0β0)s0 superspace group. Ferroelectric phase III is commensurate with q = 2/3b~* and Cc(0β0)0 symmetry. Polar phase IV is incommensurately modulated with β varying from 0.66 to 0.70 and Cc(0β0)0 superspace group. In all phases only first-order satellites are observed along the b* direction. Two types of periodic deformation are present in the structure of modulated phases. The 4-aminopyridinium cations are subjected to occupation modulation whereas [SbCl_4]_n~- chains are displacively modulated. The paraelectric-ferroelectric phase transition is an example of the incommensurate-commensurate transition of the lock-in type. A new mechanism for this transformation is proposed.
机译：关于铁电[4-NH_2C_5H_4NH] [SBCL_4]晶体结构的新X射线衍射研究表明，在覆盖三个中间相的240至304k的宽温度范围内，调节晶体结构。通过调节载体Q =βB〜*，β不同于0.60至0.66和单斜晶型C2 / C（0β0）S0超空组，相当调制II期。铁电相III与Q = 2 / 3B〜*和CC（0β0）0对称性相称。极性相IV与0.66〜0.70和CC（0β0）0超空组的β变化。在所有阶段中，只沿B *方向观察一阶卫星。在调节相的结构中存在两种类型的周期性变形。对4-氨基吡啶鎓阳离子进行职业调制，而[Sbcl_4] _N〜-Chains流动调制。近电极 - 铁电相转变是锁定型锁定类型的不计的常规转变的一个例子。提出了这种转变的新机制。

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