Growth of [010] oriented urea-doped triglycine sulphate (Ur-TGS) single crystals below and above Curie temperature (Tc) and comparative investigations of their physical properties

Abstract

Optically transparent, urea (5 wt%)-doped triglycine sulphate (Ur-TGS) single crystals were grown along polar axis [010] by Sankaranarayanan–Ramasamy unidirectional solution growth method, below and above its Curie temperature Tc = 49.3 °C. Higher growth rate of 5 mm/day was obtained for Ur-TGS crystal grown above Tc. The phase of the grown crystals was confirmed by powder XRD. P–E hysteresis studies show well-saturated hysteresis loop for crystal grown below Tc, and the remnant polarization was 0.60 µC/cm2 with a coercive field of 1.5 kV/cm. The piezoelectric d33 coefficient for Ur-TGS crystal grown below and above Tc was 25 pC/N and 35 pC/N, indicating improved piezoelectric properties of the latter. Dielectric permittivity for Ur-TGS crystal grown above Tc was approximately 10 times higher as compared to the crystal grown below Tc. Improved Vickers microhardness and lower Meyer’s index (n) were observed for Ur-TGS crystal grown above Tc. The etch pit density (EPD) of Ur-TGS crystal grown below and above Tc was 1.8 and 1.1 × 102 dislocations/cm2, respectively, indicating that the quality of the crystals grown above Tc was better than the crystal grown below Tc. The optical transmittance of Ur-TGS crystal grown above Tc was slightly (~ 5%) more than that of crystal grown below Tc. Overall, it is concluded that the higher growth rate and improved physical properties of Ur-TGS crystal grown above its Curie temperature show its suitability for the ferroelectric device applications.