Vikash Kushwaha

Potassium dihydrogen phosphate is well‐known to exhibit ferroelectricity, while ammonium dihydrogen phosphate is an antiferroelectric material, with both of them exhibiting a phase transition to paraelectric phase below room temperature. In this work, we report the synthesis and room‐temperature ferroelectric behavior of an aminophosphonium dihydrogen phosphate of formula, [{P(NHPh) ₄ (H ₂ PO ₄ )·(CH ₃ OH) _0.5 ] ( TAPDP·(CH ₃ OH) _0.5 ) that exhibits a three‐dimensional pillared‐layered hydrogen bonding network. (TAPDP·(CH ₃ OH) _0.5 crystallizes in the polar monoclinic P 2 ₁ space group, and its non‐centrosymmetric structure was confirmed by second‐harmonic generation (SHG) measurements. The ferroelectric behavior was further verified through polarization–electric field ( P–E ) loop measurements, with a saturation polarization of 21.40 µC cm ⁻² . Structural analysis combined with preliminary density functional theory calculations indicates a ferrielectric‐type ordering in which the adjacent layers exhibit different polarization directions but with unequal dipole moments. Furthermore, the electromechanical energy‐harvesting properties of TAPDP·(CH ₃ OH) ₀ . ₅ were explored in its composites with the polydimethylsiloxane (PDMS) polymer. The 10 wt% TAPDP·(CH ₃ OH) ₀ . ₅ – PDMS device exhibited a maximum peak‐to‐peak open‐circuit voltage (𝑉 _oc ) of 10.69 ± 0.04 V and the output work efficiency parameter (OWE) of 9.63%. Owing to the superior signal sensitivity of this device, a contact‐type sensor was developed to measure a motor's revolutions per minute (RPM) at both low and high speeds.

Potassium dihydrogen phosphate is well‐known to exhibit ferroelectricity, while ammonium dihydrogen phosphate is an antiferroelectric material, with both of them exhibiting a phase transition to paraelectric phase below room temperature. In this work, we report the synthesis and room‐temperature ferroelectric behavior of an aminophosphonium dihydrogen phosphate of formula, [{P(NHPh) ₄ (H ₂ PO ₄ )·(CH ₃ OH) _0.5 ] ( TAPDP·(CH ₃ OH) _0.5 ) that exhibits a three‐dimensional pillared‐layered hydrogen bonding network. (TAPDP·(CH ₃ OH) _0.5 crystallizes in the polar monoclinic P 2 ₁ space group, and its non‐centrosymmetric structure was confirmed by second‐harmonic generation (SHG) measurements. The ferroelectric behavior was further verified through polarization–electric field ( P–E ) loop measurements, with a saturation polarization of 21.40 µC cm ⁻² . Structural analysis combined with preliminary density functional theory calculations indicates a ferrielectric‐type ordering in which the adjacent layers exhibit different polarization directions but with unequal dipole moments. Furthermore, the electromechanical energy‐harvesting properties of TAPDP·(CH ₃ OH) ₀ . ₅ were explored in its composites with the polydimethylsiloxane (PDMS) polymer. The 10 wt% TAPDP·(CH ₃ OH) ₀ . ₅ – PDMS device exhibited a maximum peak‐to‐peak open‐circuit voltage (𝑉 _oc ) of 10.69 ± 0.04 V and the output work efficiency parameter (OWE) of 9.63%. Owing to the superior signal sensitivity of this device, a contact‐type sensor was developed to measure a motor's revolutions per minute (RPM) at both low and high speeds.

The development of ferroelectric materials is fundamentally constrained by the stringent requirement for crystallization within polar space groups. Moreover, integrating multiple functionalities, such as ferroelectricity, piezoelectricity, and negative thermal expansion (NTE), into a single‐component organic material remains a significant challenge, despite the demand for sustainable, wearable, high‐precision electronics. In this study, we report a symmetry‐breaking strategy to transform para‐halogenated 3‐oxo‐2‐phenylhydrazineyline indolines from centrosymmetric to polar space groups via controlled oxidation. The novel isostructural oxo‐derivatives exhibit robust ferroelectricity ( P _s and E _c ranging from 1.3 to 6.3 µC .cm ⁻² and 4 to 9.6 kV.cm ⁻¹ , respectively), supported by quantum‐mechanical calculations. Detailed crystal structure analysis reveals the mechanisms governing their polarization and ferroelectric domain switching. Leveraging its superior polarization, the chloro‐analog‐based device demonstrated high‐performance memristive behavior with stable bipolar resistive switching at minimal bias (∼1 V). The piezoelectric nanogenerators demonstrated superior energy‐harvesting capabilities, including rapid charging and high power density (up to 4.23 µW.cm ⁻² ). Additionally, bromo‐ and iodo‐analogs experienced moderate to colossal axial NTE, and all three analogs displayed minimal volumetric expansion. This study represents the first demonstration of single‐component organic materials that unite ferroelectric, piezoelectric, and NTE properties, providing a blueprint for multifunctional, high‐precision micro‐ and nanoelectronics.