Unique Design Strategy for Dual Phase Transition That Successfully Validates Dual Switch Implementation in the Dielectric Material

Integrated Reversible Thermochromism, High Tc , Dielectric Switch and Narrow Band Gap in One Multifunctional Ferroic

Organic-inorganic Hybrid (OIH) materials for multifunctional switchable applications have attracted enormous attention in recent years due to their excellent optoelectronic properties and good structural tunability. However, it still remains challenging to fabricate one simple OIH compound with multi-functionals properties, such as dielectric switching, thermochromic properties, semiconductor characteristics and ferroelasticity. Under this context, we successfully synthesized [2-(2-fluorophenyl)ethan-1- ammonium]₂ SnBr₆ (compound 1), which has a higher phase transition temperature of 427.7 K. Additionally, it exhibits a semiconducting property with an indirect band gap of 2.36 eV. Combining ferroelastic, narrow band gap, thermochromic, and dielectric properties, compound 1 can be considered as a rarely reported multi-functional ferroelastic material, which is expected to give inspiration for broadening the applications in the smart devices field.

Metal ion modulation triggers dielectric double switching and green fluorescence in A2MX4-type compounds

Multifunctional switching materials show great potential for applications in sensors, smart switches, and other fields due to their ability to integrate different physical channels in one single device. However, multifunctional responsive materials with multiple switching and luminescence properties have rarely been reported. Here, we report three organic-inorganic hybrids: [TMAA]₂[CoCl₄] (compound 1), [TMAA]₂[CdBr₄] (compound 2) and [TMAA]₂[MnCl₄] (compound 3). Compound 1 and compound 2 undergo two reversible phase transitions at high temperature (328.95/359.25 K and 350.45/393.15 K, respectively). Since the inorganic skeleton has a strong influence on the luminescence properties of such structured substances, Cd and Co were replaced with Mn, after which compound 3 was obtained as expected. The above strategy triggered bright green luminescence with a quantum yield of 35.19%, and significantly increased the phase transition temperature of compound 3 to above 400 K. The above results show that the regulation of the inorganic skeleton provides a new strategy for researchers to develop dual phase change/luminous materials.

2D lead-free organic–inorganic hybrid exhibiting dielectric and structural phase transition at higher temperatures

A novel switchable molecular dielectric material [3-3-difluorocyclobutylammonium]2CdCl4 was synthesized. It shows a reversible phase transition at 353.95 K and rapid switching and reversibility between high and low dielectric states for several cycles.

A novel organic–inorganic hybrid phase transition compound based on 4-ethylmorpholine with switchable dielectric and luminescent properties

[4-Ethylmorpholine]2MnCl4 shows a significant thermal hysteresis in the phase transition with switchable dielectric and luminescent properties.

Semi-conductive, Switchable Dielectric and Photoluminescent Properties of Two High-Temperature Phase Transition Hybrids

Bistable switches (electrical switching between "ON" and "OFF" bistable states) have gradually developed into an ideal category of highly intelligent materials, due to their significant applications in optical technology, signal processors, data storage and other switchable media applications in the field of electrical devices. Here, we successfully designed and synthesized [(FC₆ H₄ C₂ H₄ NH₃ )₂ MCl₄ ]_n (FC₆ H₄ C₂ H₄ NH₃ ⁺ )=deprotonated 4-fluoro- phenethylamine; M=Cd (1), Mn (2)), which realized the coupling of thermo-dielectric switching characteristics, semi-conductor characteristics and photo-luminescent properties. DSC (differential scanning calorimetry) and dielectric measurements show that 1 is a sensitive dielectric bistable switch between the high dielectric (ON) and low dielectric (OFF) states. The temperature-variable single crystal structure shows that the both 1 and 2 undergo a high-temperature reversible phase transition around 383 K/380 K, which is caused by the order-disordered transformation of organic cations and the slight distortion of the inorganic framework. In particular, 1 shows outstanding switchable dielectric behavior and semiconducting properties. Further, 1 and 2 emit strong green and yellow luminescence at 527 and 595 nm, respectively.

Two In-based organic-inorganic hybrid compounds with reversible phase transition derived from the order-disorder changes of cations or anions

Solid-state phase transition materials have received extraordinary interest due to their rich physical properties, such as thermal, dielectric, and ferroelectric properties. Here, two In-based organic-inorganic hybrid compounds, (C₆H₅CH₂CH₂NH₃)₃[InBr₅(H₂O)] (1) and [(C₃H₇)₄N][InCl₄] (2), both display reversible phase transition and dielectric response. Differential scanning calorimetry measurements indicate that the phase transition temperatures (T_c) of 1 and 2 are 167 K and 351 K, respectively. Moreover, structural analyses disclose that the phase transition of 1 can be attributed to the order-disorder changes of phenethylammonium organic cations whereas the phase transition of 2 is caused by the order-disorder changes of [InCl₄]^- anions. The phase transitions of In-based organic-inorganic hybrid compounds can be driven by the order-disorder changes of cations or anions. Therefore, the system of In-based organic-inorganic hybrid compounds is very suitable for exploring organic-inorganic hybrid phase transition materials.

A-site cation with high vibrational motion in ABX3 perovskite effectively induces dielectric phase transition

A hybrid perovskite material with dielectric phase transition obtained by the introduction of a moving group.

Multisequential reversible phase transition materials with semiconducting and fluorescence properties: (C8H18BrN)2SnBr6

A novel organic–inorganic hybrid metal halide has synthesized, namely (C8H18BrN)2SnBr6 (1), which have excellent switchable dielectric properties, narrow band gap and broadband yellow fluorescence characteristics.

Phosphonium-Based One-Dimensional Perovskite with Switchable Dielectric Behaviors and Phase Transitions

The one-dimensional (1D) ABX₃-type perovskite [(CH₃)₃PCH₂F]CdCl₂Br (1) has been obtained on the basis of the design of an organic-inorganic hybrid. Strikingly, it experiences sequential phase transitions at around 295 and 336 K, respectively. Given the noticeable steplike dielectric anomalies in the vicinity of 295 K, 1 is identified as a promising dielectric-switchable material. According to the single-crystal structure analysis, the order-to-disorder transformation of the [(CH₃)₃PCH₂F]⁺ cation is the main reason for the phase transitions and the change of space group from the orthorhombic Pnma (No. 62) to the hexagonal P6₃/m (No. 176). This design of a perovskite structure will inspire more advances in the ever-growing field of switchable functional materials.

Methylation Design Strategy to Trigger a Dual Dielectric Switch and Improve the Phase Transition Temperature

Phase transitions of hybrid materials have aroused widespread concern and call for an in-depth study on its structure design, because the structure and characteristics are closely related, which promote potential applications in the field of temperature sensors, dielectric switches, and actuators. However, designing materials with multiple phase transitions and a high phase transition temperature (Tr) remains a huge challenge. In order to deal with this key hurdle, we tried to regulate the structural components and successfully synthesized [MASD]₂[CdCl₄] (1, MASD = 8-methyl-5-azoniaspiro[4,5]decane), which displays multiple phase transitions occurring at 273.8 K and 395.9 K separately. The Tr has significantly increased compared with the parent compounds reported previously. As the temperature sensitivity of compound 1 is constant at different frequencies, it can be applied for detectors or sensors under frequency-independent or wide frequency conditions. Moreover, methylation design strategy evidently triggered the dual dielectric switch and improved the Tr, which opens a new path for finding and adjusting ideal materials of multiple phase transition.