Influence of chemical purification methodologies on the Bridgman growth of trans-stilbene (TSB) crystal, and feasibility studies for X-ray imaging and neutron/gamma discrimination applications

Abstract

Growth of large size, good optical quality, technologically important organic single crystal of trans-Stilbene (TSB) by Bridgman technique has been reported. To evaluate the influence of chemical purity on the growth process, multiple growth runs were conducted, each using starting materials of varying purity levels. A crack-free, transparent, and colorless crystal was grown using chemical obtained through a meticulous double-purification process involving recrystallization and zone melting. The grown crystal was precisely cut and polished to obtain elements for experimental investigations, targeting applications in X-ray imaging and Pulse Shape Discrimination (PSD). Additional plates were prepared for investigations of phase purity by powder XRD, crystalline perfection by high resolution X-ray diffraction (HRXRD), and optical quality using birefringence interferometry and UV–Vis transmission studies, all pointing towards low defects, and hence good optical quality. The crystal’s optical energy gap was determined to be 3.47 eV by Tauc plot. Photoluminescence (PL) studies using 325 nm excitation revealed a broad emission, with a prominent peak around 380 nm. Time Correlated Single Photon Counting (TCPCS) studies were performed to quantify the decay characteristics of the crystal. The analysis reveals dual decay times of 1.98 ns and 4.14 ns. Importantly, strong scintillation output was measured using X-rays from Indus-2 synchrotron radiation beamline, enabling the resolution of fine object features of as small as 100 µm, highlighting its suitability for X-ray imaging. Furthermore, PSD characterization performed using Am-Be radioactive source confirmed the crystal’s potential for neutron/gamma (n/γ) discrimination applications, making it a promising candidate for advanced technological applications.