Doping-Driven Suppression of the Metal–Insulator Transition in PrNiO₃: Comparing Experiment and Bond-Percolation Modeling

Praseodymium nickelate (PrNiO₃), part of the rare-earth perovskite nickelate series RNiO₃, lies near the metal–insulator (M-I) transition boundary, making it an ideal model for studying how electronic correlations respond to lattice strain and substitutional doping. In this study, we examine isoelectronic and hole-doped series Pr₁₋ₓAₓNiO₃ (A = Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, La³⁺, Eu³⁺) to probe how dopant size and valency influence structural, electronic, and magnetic behaviors. Polycrystalline samples were synthesized via a sol–gel nitrate/citrate precursor and annealed under high oxygen pressure (150-200 bar) at 900-1000°C to ensure phase purity and stoichiometric control. To interpret the observed transitions, we extend the bond-percolation model¹ originally applied to La₁₋ₓRₓNiO₃, in which smaller R ions disrupt conductive Ni-O-Ni bonds. In our simple model, large-scale simulations using the Depth First Search algorithm reveal that correlated bond breaking lowers the percolation threshold to a critical bond fraction p_c ≈ 0.171 at a small-ion concentration x ≈ 0.36. By integrating doping experiments with percolation modeling, this study links ionic size, Ni-O-Ni connectivity, and M-I suppression to tune nickelates toward novel quantum ground states, including possible superconductivity.

1. Gregorio Ponti, Holland Frieling, Sara J. Irvine, Lucas P. Moynihan, Jonathan D. K. Tebo, Quinn D. B. Timmers and John T. Markert, “Suppression of Conductivity in Isovalent-Rare-Earth Substituted Nickelates: Approaching an Apparent T → 0 Bond-Percolation Transition,” Japanese Physics Society Conference Proceedings 38, 011040 (2023).