Journal
JOURNAL OF MATERIALS CHEMISTRY C
Volume 10, Issue 46, Pages 17567-17576Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/d2tc02708a
Keywords
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Funding
- Fundacao Cearense de Apoio ao Desenvolvimento Cientifico e Tecnologico [FUNCAP/PRONEX PR2-0101-00006.01.00/15]
- Conselho Nacional de Pesquisa e Desenvolvimento do Brasil (CNPq) [140390/2019-7]
- Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior do Brasil (CAPES) [001 (CAPES - Projeto 88882.349932/2019-01)]
- Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [2019/21939-0]
- FAPEMA [COOPI-07771/17, BPD-05073]
- Ministerio de Economia y Competitividad (MINECO)
- EU-FEDER [MAT2017-86453-R]
- Xunta de Galicia [ED431G/09]
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The study revealed the first-order structural phase transition undergone by [(CH3)(2)NH2]PbBr3 at 250 K, exhibiting an unusual uniaxial thermal expansion mechanism related to its 4H-hexagonal perovskite structure. Raman spectroscopy indicated a weakening of H-bond interactions between the DMA cation and the framework upon heating, playing a fundamental role in the phase transition to the disordered high-temperature phase.
We have investigated the first-order structural phase transition undergone by [(CH3)(2)NH2]PbBr3 at T = 250 K and its lattice dynamics using both temperature-dependent synchrotron X-ray powder diffraction (SXRPD) and Raman spectroscopy techniques. Very interestingly, we find that this compound exhibits an unusual uniaxial thermal expansion, which we relate to the structural arrangement of the bioctahedron [Pb2Br9](5-) units in this 4H-hexagonal perovskite, which favors the elongation of the PbBr3- framework parallel to the ab plane, and the shrinkage of the bioctahedron [Pb2Br9](5-) units along the crystal c-axis upon heating. This novel thermomechanical mechanism differs from the typical wine-rack one described so far in other perovskite materials. Additionally, we have studied the lattice dynamics in this compound by Raman spectroscopy, probing the presence of a H-bond between the DMA cation and the framework. Our findings suggest that intermolecular interactions weaken upon heating, which plays a fundamental role in the phase transition to the disordered high-temperature phase.
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