Designing high-performance thermistor manganites: a review of charge transport, TCR enhancement, and materials engineering strategies

Abstract

This work presents a comprehensive investigation of the electrical transport, temperature coefficient of resistance (TCR), and thermistor parameters of manganite perovskites, with particular emphasis on the roles of dopant nature, dopant concentration, annealing temperature, and A-site deficiency. The results reveal that charge transport is governed by Mott variable range hopping (Mott-VRH) at low temperatures and thermally activated small polaron hopping (SPH) at high temperatures, with well-defined crossovers through the intermediate Shklovskii–Efros variable range hopping (ES-VRH) regime associated with Coulomb-gap effects. A strong tunability of electrical behavior is achieved through compositional and processing control. The nature of A- and B-site dopants significantly modifies lattice distortion, Mn–O–Mn bond geometry, and carrier concentration, thereby controlling conductivity order and activation energy. The increase in dopant concentration alters the Mn³⁺/Mn⁴⁺ ratio and shifts the metal–semiconductor transition, while annealing temperature governs grain connectivity and defect density, leading to substantial changes in transport mechanisms. A-site deficiency further enhances carrier mobility and induces notable modifications in both conductivity and transition temperatures. TCR analysis demonstrates both NTCR and PTCR behaviors, with exceptionally high NTCR values reaching −35%·K⁻¹. The thermistor parameters exhibit wide ranges, with activation energies of 47–290 meV, β values of 545–3366 K, and sensitivity coefficients of up to −3.74%·K⁻¹. A clear correlation between E_a, β, α, and TCR confirms the thermally activated nature of conduction and highlights the role of structural disorder and electron–phonon interactions. These findings establish manganites as highly tunable functional materials and promising candidates for thermistors, infrared sensors, and advanced electronic applications.