Matches in SemOpenAlex for { <https://semopenalex.org/work/W2117320601> ?p ?o ?g. }
- W2117320601 endingPage "1158" @default.
- W2117320601 startingPage "1146" @default.
- W2117320601 abstract "Abstract We present three Mg–formate frameworks, incorporating three different ammoniums: [NH 4 ][Mg(HCOO) 3 ] ( 1 ), [CH 3 CH 2 NH 3 ][Mg(HCOO) 3 ] ( 2 ) and [NH 3 (CH 2 ) 4 NH 3 ][Mg 2 (HCOO) 6 ] ( 3 ). They display structural phase transitions accompanied by prominent dielectric anomalies and anisotropic and negative thermal expansion. The temperature‐dependent structures, covering the whole temperature region in which the phase transitions occur, reveal detailed structural changes, and structure–property relationships are established. Compound 1 is a chiral Mg–formate framework with the NH 4 + cations located in the channels. Above 255 K, the NH 4 + cation vibrates quickly between two positions of shallow energy minima. Below 255 K, the cations undergo two steps of freezing of their vibrations, caused by the different inner profiles of the channels, producing non‐compensated antipolarization. These lead to significant negative thermal expansion and a relaxor‐like dielectric response. In perovskite 2 , the orthorhombic phase below 374 K possesses ordered CH 3 CH 2 NH 3 + cations in the cubic cavities of the Mg–formate framework. Above 374 K, the structure becomes trigonal, with trigonally disordered cations, and above 426 K, another phase transition occurs and the cation changes to a two‐fold disordered state. The two transitions are accompanied by prominent dielectric anomalies and negative and positive thermal expansion, contributing to the large regulation of the framework coupled the order–disorder transition of CH 3 CH 2 NH 3 + . For niccolite 3 , the gradually enhanced flipping movement of the middle ethylene of [NH 3 (CH 2 ) 4 NH 3 ] 2+ in the elongated framework cavity finally leads to the phase transition with a critical temperature of 412 K, and the trigonally disordered cations and relevant framework change, providing the basis for the very strong dielectric dispersion, high dielectric constant (comparable to inorganic oxides), and large negative thermal expansion. The spontaneous polarizations for the low‐temperature polar phases are 1.15, 3.43 and 1.51 μC cm −2 for 1 , 2 and 3 , respectively, as estimated by the shifts of the cations related to the anionic frameworks. Thermal and variable‐temperature powder X‐ray diffraction studies confirm the phase transitions, and the materials are all found to be thermally stable up to 470 K." @default.
- W2117320601 created "2016-06-24" @default.
- W2117320601 creator A5007599353 @default.
- W2117320601 creator A5035348848 @default.
- W2117320601 creator A5039657597 @default.
- W2117320601 creator A5088660854 @default.
- W2117320601 date "2013-12-16" @default.
- W2117320601 modified "2023-10-18" @default.
- W2117320601 title "Phase Transitions, Prominent Dielectric Anomalies, and Negative Thermal Expansion in Three High Thermally Stable Ammonium Magnesium-Formate Frameworks" @default.
- W2117320601 cites W1670329995 @default.
- W2117320601 cites W1895463043 @default.
- W2117320601 cites W1963893386 @default.
- W2117320601 cites W1965213950 @default.
- W2117320601 cites W1967585041 @default.
- W2117320601 cites W1976775143 @default.
- W2117320601 cites W1979681627 @default.
- W2117320601 cites W1981267686 @default.
- W2117320601 cites W1983458676 @default.
- W2117320601 cites W1984543372 @default.
- W2117320601 cites W1985656278 @default.
- W2117320601 cites W1989824100 @default.
- W2117320601 cites W1991812747 @default.
- W2117320601 cites W1992295247 @default.
- W2117320601 cites W1993146835 @default.
- W2117320601 cites W1995103466 @default.
- W2117320601 cites W1995365123 @default.
- W2117320601 cites W1998523963 @default.
- W2117320601 cites W2001682945 @default.
- W2117320601 cites W2006135980 @default.
- W2117320601 cites W2009806571 @default.
- W2117320601 cites W2011372511 @default.
- W2117320601 cites W2015079217 @default.
- W2117320601 cites W2016713349 @default.
- W2117320601 cites W2018453043 @default.
- W2117320601 cites W2018648485 @default.
- W2117320601 cites W2022167379 @default.
- W2117320601 cites W2025697658 @default.
- W2117320601 cites W2029469190 @default.
- W2117320601 cites W2033455237 @default.
- W2117320601 cites W2033698433 @default.
- W2117320601 cites W2037282243 @default.
- W2117320601 cites W2039724172 @default.
- W2117320601 cites W2046305476 @default.
- W2117320601 cites W2051271391 @default.
- W2117320601 cites W2052538205 @default.
- W2117320601 cites W2052767734 @default.
- W2117320601 cites W2052896778 @default.
- W2117320601 cites W2053225929 @default.
- W2117320601 cites W2056920604 @default.
- W2117320601 cites W2058568474 @default.
- W2117320601 cites W2059233014 @default.
- W2117320601 cites W2059841912 @default.
- W2117320601 cites W2061396943 @default.
- W2117320601 cites W2062269633 @default.
- W2117320601 cites W2063871837 @default.
- W2117320601 cites W2068282876 @default.
- W2117320601 cites W2069537362 @default.
- W2117320601 cites W2075508377 @default.
- W2117320601 cites W2076378858 @default.
- W2117320601 cites W2076564072 @default.
- W2117320601 cites W2077099196 @default.
- W2117320601 cites W2077778142 @default.
- W2117320601 cites W2079111496 @default.
- W2117320601 cites W2079154936 @default.
- W2117320601 cites W2082498611 @default.
- W2117320601 cites W2083242163 @default.
- W2117320601 cites W2083833353 @default.
- W2117320601 cites W2084589051 @default.
- W2117320601 cites W2084615665 @default.
- W2117320601 cites W2087898925 @default.
- W2117320601 cites W2089556499 @default.
- W2117320601 cites W2091161882 @default.
- W2117320601 cites W2092865692 @default.
- W2117320601 cites W2097068051 @default.
- W2117320601 cites W2098292174 @default.
- W2117320601 cites W2100245048 @default.
- W2117320601 cites W2108219971 @default.
- W2117320601 cites W2109012502 @default.
- W2117320601 cites W2111887934 @default.
- W2117320601 cites W2112185747 @default.
- W2117320601 cites W2121904540 @default.
- W2117320601 cites W2122179865 @default.
- W2117320601 cites W2122349947 @default.
- W2117320601 cites W2147673995 @default.
- W2117320601 cites W2149632585 @default.
- W2117320601 cites W2155334117 @default.
- W2117320601 cites W2160348894 @default.
- W2117320601 cites W2165419343 @default.
- W2117320601 cites W2166419930 @default.
- W2117320601 cites W2281708829 @default.
- W2117320601 cites W2313570818 @default.
- W2117320601 cites W2313776156 @default.
- W2117320601 cites W2315040572 @default.
- W2117320601 cites W2316897572 @default.
- W2117320601 cites W2318491733 @default.
- W2117320601 cites W2322856380 @default.
- W2117320601 cites W2327753501 @default.
- W2117320601 cites W2328706819 @default.