Unidirectional crystal growth of L-alanine doped triglycine sulphate crystals along [010] polar direction in ferroelectric and paraelectric temperature ranges, and their comparative characterizations

Abstract Good quality, large size (010) polar face oriented ferroelectric single crystals of L-alanine doped triglycine sulphate (LA-TGS) were grown by unidirectional solution growth technique in two temperature regimes on either side of its Curie temperature (Tc). The growth conditions were optimized to obtain LA-TGS crystals of length = 40 mm, diameter = 30 mm below Curie temperature (Tc), and length = 50 mm, diameter = 15 mm above Curie temperature, with growth rates of 1.3 and 3.0 mm/day, respectively. Powder XRD was performed for phase confirmation and DTA for phase transition temperature determination, and compared with data of undoped TGS crystal. Crystal grown below Tc has almost same dislocations density, two times higher piezoelectric d33 coefficient, and three times lower dielectric permittivity as compared to the crystal grown above Tc, showing its better device potential. The UV-Vis-NIR transmittance of the two crystals was ≥80%, showing their good optical quality.