Effect of stoichiometry and calcination method on phase transition and optical and dielectric properties of Pby(ZrxTi1-x)O3 nanoparticles synthesized by sol–gel technique

• Pb y (Zr x Ti 1-x )O 3 nanoparticles with stoichiometry of y = 0.5, 1 and x = 0.5, 0.55, 0.6. • To investigate dielectric, optical, and nano-structural properties. • Study of phase structure, crystallite size, strain, and morphology of nanostructure. • Optical absorption (α), extinction (k), complex refractive index ( n ∼ ), complex dielectric ( ∊ ∼ ). In this study, Pb y (Zr x Ti 1-x )O 3 nanoparticles with stoichiometry of y = 0.5, 1 and x = 0.5, 0.55, 0.6, were synthesized by the sol–gel method and calcinated by furnace at T = 500 °C, 700 °C, 900 °C, and microwave in P = 900 W to investigate dielectric, optical, and nano-structural properties. The XRD, EDX, and FESEM analyses were used for phase structure, crystallite size, strain, and morphology of nanostructure. The optical properties, including optical absorption (α) and extinction coefficients (k), complex refractive index ( n ∼ ), complex dielectric function ( ∊ ∼ ), bandgap (E g ), and dielectric loss tangent (tan δ), were studied by UV–Vis spectrometer. For y = 1 at T = 900 °C, phase-pure perovskite with high crystallinity is formed, near the morphotropic phase boundary (MPB), whereas in y = 0.5, ZrO 2 /PbO is often retained ZrO 2 /PbO and at x = 0.6, it separates into the PbZrO 3 and PbTiO 3 independent phases. For y = 0.5 and x = 0.5, the optical bandgap evolved from ∼ 1.9 to ∼ 2.55 eV with temperature, and for Zr-rich PZT with x = 0.6, it showed a higher absorption coefficient and lower optical bandgap, consistent with defect-assisted absorption. Refractive index raised under microwave for all x and it decreased under the furnace post-annealing, especially for y = 1. The dielectric loss tangent (tan δ) decreased after annealing in furnace for y = 1, but increased with temperature for y = 0.5. Urbach energy (E U ) , as a disorder metric, decreased from 128–145 meV to 95–118 meV and 86–92 meV, after calcination in furnace and microwave, respectively. The results of porosity of nanoparticles for y = 1, with calcination in furnace, have shown a dense state and reproducible (9–10 %), whereas for y = 0.5 high porosity from 30.8 to 25.8 % for x = 0.50 to 0.60 and more porosity by microwave for y = 0.5, x = 0.55 (∼34.9 %). The combination of high n , and low k , ε 2 , tan δ and engineered porosity for y = 1 and x = 0.50 to 0.55, after calcination in furnace at T = 900 °C, introduces as strong high-index layers for Distributed Bragg Reflector (DBR) mirrors.