Synthesis and Characterization of

Calcium zirconate (CaZrO3) nanoparticles (CZNPs) were successfully synthesized using a microwave-assisted combustion method employing L-serine as a fuel and reducing agent. The rapid combustion process yielded highly porous, phase-pure CaZrO3 with an orthorhombic structure, as confirmed by PXRD and Rietveld refinement, with crystallite sizes ranging between 20–25 nm. FE-SEM and TEM analyses revealed irregular, agglomerated nanoparticles with abundant pores arising from gaseous release during combustion, while HRTEM and SAED patterns confirmed their high crystallinity. FTIR spectra evidenced the formation of characteristic Ca-O and Zr-O vibrational modes. Diffuse reflectance spectroscopy combined with Kubelka-Munk analysis indicated a direct band gap of 5.2 eV. The X-ray and gamma attenuation characteristics of CZNPs were evaluated experimentally using multiple radioactive sources (133Ba, 22Na, 137Cs, and 57Co) and compared with theoretical values derived from Hubbell data. Good agreement was observed above 400 keV, while deviations below 400 keV highlighted the influence of nanoparticle size on photon interaction. Antimicrobial performance was assessed against Bacillus cereus and Pseudomonas aeruginosa, demonstrating dose-dependent inhibition with prominent zones of inhibition (15 mm and 11 mm at 25 mg/mL). The combined results confirm CaZrO3 nanoparticles as promising candidates for antimicrobial applications and radiation shielding materials.