Structural, Optical, and Conduction Relaxation Properties of TlCrP₂O₇ Driven by Nonoverlapping Small Polaron...

This work provides an in-depth examination of the structural, optical, electrical, and dielectric characteristics of TlCrP₂O₇, prepared using a conventional solid-state reaction route. X-ray diffraction (XRD) analysis confirms the formation of a highly crystalline single phase with monoclinic symmetry (P2₁/c). Complementary Raman and infrared spectroscopy further validate the structural framework and reveal the characteristic internal and external vibrational modes associated with the pyrophosphate network. Optical characterization revealed a direct band gap of 2.99 eV and an Urbach energy of 0.48 eV, reflecting significant electronic transitions within the lattice. Impedance measurements indicated thermally activated conduction, with activation energies of 0.52 eV for grains and 0.47 eV for grain boundaries, successfully modeled using an equivalent circuit incorporating constant phase elements to capture microstructural effects. The AC conductivity obeys Jonscher's universal power law, indicating that charge transport occurs through a nonoverlapping small polaron tunneling mechanism. Dielectric studies reveal pronounced non-Debye relaxation and significant space-charge polarization, both strongly influenced by temperature, frequency, and grain-boundary effects. Overall, these results emphasize the crucial influence of microstructure on charge transport and dielectric behavior, highlighting TlCrP₂O₇ as a promising material for electronic and optoelectronic applications.