Mechanical investigations on piezo-/ferrolectric maleic acid-doped triglycine sulphate single crystal using nanoindentation technique

Abstract

The present work reports the growth and characterization of single crystals of pure triglycine sulphate (TGS) and maleic acid doped triglycine sulfate (MA-TGS). Both the crystals were grown by conventional slow evaporation solution technique. The crystal structure, composition and morphology of both pure TGS and MA-TGS crystals were studied using single crystal and powder X-ray diffraction, scanning electron microscope, and CHNS analysis. The results revealed monoclinic crystal system for both the crystals with space group P21. Thermal stability and melting point of the grown crystals were determined by employing thermogravimetric and differential thermal analysis (TG-DTA) technique. The dielectric study showed an increase in Curie temperature along with a decrease in maximum permittivity due to MA doping. Enhanced piezoelectric, ferroelectric and mechanical properties were obtained for the doped crystal. The value of piezoelectric charge coefficient, d22 was estimated from ‘Displacement-Voltage (D-V)’ butterfly curves and was observed to increase from 56.23 pm/V for pure TGS single crystal to 72.02 pm/V for MA-TGS single crystal. An increase in the ferroelectric parameters (spontaneous and remanent polarizations) was observed for doped TGS crystal. Also, the value of true-remanent polarization was determined using remanent hysteresis task for MA-TGS crystal. Mechanical stability of grown crystals was examined using the nanoindentation technique and various parameters such as the hardness, stiffness and Young’s modulus were evaluated. Nanoindentation results revealed that both the crystals have a greater capability to withstand deformation caused by applying various loads. However, the mechanical strength of MA-TGS crystal was observed to be better than that of pure TGS crystal. Comparative structural, ferroelectric, piezoelectric and mechanical studies provide useful scientific information of an important class of TGS crystals.