Physicochemical investigation of semi-organic urotropine p -nitrophenolate phosphoric acid trihydrate single crystal: Optical, dielectric, thermal, and mechanical studies

Semi-organic single crystal of UPPAT was investigated for their structural and physicochemical properties Single-crystal XRD confirmed a monoclinic P2₁/c structure, and the crystal exhibited high transparency with a 2.5 eV band gap. At 1100 nm, the refractive index and extinction coefficient were 2.70 and 2.59 × 10−3 respectively. The dielectric constant and dielectric loss were measured as function of frequency and temperature. The UPPAT crystal exhibited a work-hardening coefficient of n = 2.01. Thermal studies showed that the crystal is stable up to 396.15 K. A large decomposition between 396.15 and 648.15 K confirms the breakdown of the organic framework.