Structural, electrical, ferroelectric and mechanical properties with Hirshfeld surface analysis of novel NLO semiorganic sodium p-nitrophenolate dihydrate piezoelectric single crystal

Abstract

Novel non-linear sodium para-nitrophenolate dihydrate (SPNPD) single crystals were grown by the controlled evaporation method. Various functional groups and chemical bonding were identified by FTIR and Raman analysis. Hirshfeld surface and fingerprint plots were drawn and analyzed to investigate the intermolecular interactions present in the crystal structure. UV-visible studies indicate the high transmittance of the crystals in the visible region with a wide band gap 2.80 eV. In the photoluminescence spectrum, a sharp broad emission peak centered at 525 nm indicates green emission. In the dielectric study a broad peak with low dielectric constant value was observed at 34 °C which may be due to a ferroelectric to paraelectric transition. Piezoelectricity was confirmed by determining the piezoelectric charge coefficient (d₃₃ = 2.24 pC N⁻¹). The hysteresis loop shows values of remnant polarization and coercive field of 2.67 μC cm⁻² and 7.43 kV cm⁻¹, respectively. Piezo-/ferroelectricity were reported for the first time in p-nitrophenolate based compounds. SHG efficiency of this material was found to be 4.15 times of that of KDP. The mechanical strength was confirmed from a Vicker’s microhardness study and void volume. Thus the promising piezoelectric, ferroelectric behavior of the material along with high SHG efficiency and low dielectric constant, established SPNPD as a potential material for transducer, optoelectronics and nonvolatile memory devices applications.