A-site cation substitution effects on lattice distortion and open-volume defects in Nd–Ca/Sr and Pr–Ca perovskite manganites

Jabarov S., Hakhverdiyeva Z., Samadov S., Sidorin A., Trung N., Abiyev A., ...More

Micro and Nanostructures, vol.214, 2026 (SCI-Expanded, Scopus) identifier identifier

  • Publication Type: Article / Article
  • Volume: 214
  • Publication Date: 2026
  • Doi Number: 10.1016/j.micrna.2026.208659
  • Journal Name: Micro and Nanostructures
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Keywords: Doppler broadening annihilation spectroscopy (DBAS), Electron momentum distribution (EMD), Perovskites, Positron annihilation lifetime spectroscopy (PALS), Raman spectra, X-ray diffraction (XRD)
  • Azerbaijan State University of Economics (UNEC) Affiliated: No

Abstract

Half-doped perovskite manganites with Nd/Pr on the rare-earth site and Ca/Sr on the alkaline-earth site were investigated to clarify how A-site cation chemistry governs crystal structure and open-volume defect states. Nd0.5Ca0.5MnO3, Nd0.5Sr0.5MnO3 and Pr0.5Ca0.5MnO3 were prepared and characterized by X-ray diffraction (XRD), Raman spectroscopy, positron annihilation lifetime spectroscopy (PALS), Doppler broadening annihilation spectroscopy, and electron momentum distribution (EMD) analysis. XRD confirms an orthorhombic perovskite structure for all compositions and reveals a systematic expansion of the unit-cell volume toward Sr-containing samples, consistent with the larger ionic radius of Sr2+. Raman spectra show more intense and better-resolved phonon modes for the Pr-based composition, indicating improved local structural order and modified Jahn–Teller distortions. PALS evidences a pronounced evolution of open-volume defects, with τmean positron lifetimes of 0.222 ns (Nd0.5Ca0.5MnO3), 0.233 ns (Nd0.5Sr0.5MnO3) and 0.207 ns (Pr0.5Ca0.5MnO3), identifying the Sr-containing crystal as the most defect-rich. DB and EMD results further indicate that A-site substitution alters Mn–O bond hybridization and the degree of d-electron localization. Overall, the data demonstrate that A-site cation engineering provides a direct route to tune structure–defect–electronic correlations in half-doped manganite perovskites, enabling targeted optimization for spintronic and sensing functionalities.