Liang Akun, Turnbull Robin, Popescu Catalin, Fernandez-Guillen Ismael, Abargues Rafael, Boix Pablo P, Errandonea Daniel
Departamento de Física Aplicada-ICMUV-MALTA Consolider Team, Universitat de València, c/Dr. Moliner 50, 46100 Burjassot, Valencia, Spain.
Centre for Science at Extreme Conditions and School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD, United Kingdom.
J Phys Chem C Nanomater Interfaces. 2023 Jun 21;127(26):12821-12826. doi: 10.1021/acs.jpcc.3c03263. eCollection 2023 Jul 6.
The crystal structure of the CHNHPbBr perovskite has been investigated under high-pressure conditions by synchrotron-based powder X-ray diffraction. We found that after the previously reported phase transitions in CHNHPbBr (3̅→3̅→2), which occur below 2 GPa, there is a third transition to a crystalline phase at 4.6 GPa. This transition is reported here for the first time contradicting previous studies, which reported amorphization of CHNHPbBr between 2.3 and 4.6 GPa. Our X-ray diffraction measurements show that CHNHPbBr remains crystalline up to at least 7.6 GPa, the highest pressure covered by experiments. The new high-pressure phase is also described by the space group 2; however, the transition involves abrupt changes in the unit-cell parameters and a 3% decrease of the unit-cell volume. Our conclusions are confirmed by optical-absorption experiments, by visual observations, and by the fact that pressure-induced changes up to 10 GPa are reversible. The optical studies also allow for the determination of the pressure dependence of the band-gap energy, which is discussed using the structural information obtained from X-ray diffraction.
通过基于同步加速器的粉末X射线衍射，在高压条件下研究了CHNHPbBr钙钛矿的晶体结构。我们发现，在先前报道的CHNHPbBr（3̅→3̅→2）的相变之后（这些相变发生在2 GPa以下），在4.6 GPa时会发生向结晶相的第三次转变。此处首次报道了这一转变，与先前的研究相矛盾，先前的研究报道CHNHPbBr在2.3至4.6 GPa之间会发生非晶化。我们的X射线衍射测量表明，CHNHPbBr在至少7.6 GPa（实验覆盖的最高压力）下仍保持结晶状态。新的高压相也由空间群2描述；然而，该转变涉及晶胞参数的突然变化以及晶胞体积3%的减小。我们的结论通过光吸收实验、目视观察以及高达10 GPa的压力诱导变化是可逆的这一事实得到了证实。光学研究还可以确定带隙能量对压力的依赖性，并利用从X射线衍射获得的结构信息进行了讨论。
