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Phase Transition from Weak Ferroelectricity to Incipient Ferroelectricity in Li2Sr(Nb1–xTax)2O7
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-01-15 , DOI: 10.1021/acs.chemmater.9b04022 Takayuki Nagai 1 , Yasuhide Mochizuki 2 , Hirokazu Shirakuni 1 , Akitoshi Nakano 1 , Fumiyasu Oba 2 , Ichiro Terasaki 1 , Hiroki Taniguchi 1
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-01-15 , DOI: 10.1021/acs.chemmater.9b04022 Takayuki Nagai 1 , Yasuhide Mochizuki 2 , Hirokazu Shirakuni 1 , Akitoshi Nakano 1 , Fumiyasu Oba 2 , Ichiro Terasaki 1 , Hiroki Taniguchi 1
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Pseudo Ruddlesden–Popper-type Li2SrNb2O7 undergoes a phase transition between paraelectric and weak ferroelectric phases at Tc (=217 K), whereas Ta-counterpart Li2SrTa2O7 stays paraelectric though its room temperature structure is identical to that of Li2SrNb2O7. In the present study, the ferroelectric phase transition of Li2Sr(Nb1–xTax)2O7 is investigated as a function of Ta-concentration x. As the Ta-concentration x increases, Tc is found to decrease monotonously, leading to the disappearance of the ferroelectricity at x = 0.4. This phase-transition suppression with increasing x in Li2Sr(Nb1–xTax)2O7 is supported by first-principles calculations, showing that the soft mode in Li2SrNb2O7 or the increase of x in Li2Sr(Nb1–xTax)2O7 enhances their bonding states. In the composition of x = 0.4, dielectric permittivity gradually increases on cooling to become independent of temperature around 0 K, indicating an incipient ferroelectricity of the system. Empirical analyses suggest existence of a quantum paraelectric state in a composition range of 0.3 < x < 0.4. The present study provides a novel playground to investigate a quantum para/ferroelectricity in layered-perovskite-type compounds.
中文翻译：
Li 2 Sr（Nb 1– x Ta x）2 O 7中从弱铁电到初生铁电的相变
伪Ruddlesden–Popper型Li 2 SrNb 2 O 7在T c（= 217 K）时经历顺电相和弱铁电相之间的相变，而Ta对应的Li 2 SrTa 2 O 7尽管其室温结构相同也保持顺电状态达到Li 2 SrNb 2 O 7的值。在本研究中，研究了Li 2 Sr（Nb 1– x Ta x）2 O 7的铁电相变与Ta浓度x的函数关系。。随着Ta浓度x的增加，发现T c单调降低，从而导致x = 0.4时铁电消失。此相变抑制随X的Li 2的Sr（NB 1- X钽X）2 ö 7通过第一原理计算的支持，显示出在李软模式2 SRNB 2 ö 7或增加X在李2 Sr（Nb 1– x Ta x）2 O 7增强它们的键合状态。在x = 0.4的成分中，介电常数在冷却时逐渐增加，变得独立于0 K附近的温度，表明系统的初始铁电。实证分析表明，在0.3 < x <0.4的组成范围内存在量子顺电态。本研究提供了一个新颖的游乐场，以研究层状钙钛矿型化合物的量子对位/铁电。
更新日期：2020-01-16
中文翻译：
Li 2 Sr（Nb 1– x Ta x）2 O 7中从弱铁电到初生铁电的相变
伪Ruddlesden–Popper型Li 2 SrNb 2 O 7在T c（= 217 K）时经历顺电相和弱铁电相之间的相变，而Ta对应的Li 2 SrTa 2 O 7尽管其室温结构相同也保持顺电状态达到Li 2 SrNb 2 O 7的值。在本研究中，研究了Li 2 Sr（Nb 1– x Ta x）2 O 7的铁电相变与Ta浓度x的函数关系。。随着Ta浓度x的增加，发现T c单调降低，从而导致x = 0.4时铁电消失。此相变抑制随X的Li 2的Sr（NB 1- X钽X）2 ö 7通过第一原理计算的支持，显示出在李软模式2 SRNB 2 ö 7或增加X在李2 Sr（Nb 1– x Ta x）2 O 7增强它们的键合状态。在x = 0.4的成分中，介电常数在冷却时逐渐增加，变得独立于0 K附近的温度，表明系统的初始铁电。实证分析表明，在0.3 < x <0.4的组成范围内存在量子顺电态。本研究提供了一个新颖的游乐场，以研究层状钙钛矿型化合物的量子对位/铁电。
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