Temperature Coefficient of Resistivity for Doped Manganites Towards Sustainability of Magnetic Based Temperature Sensor

Abstract

The temperature coefficient of resistivity (TCR) in perovskite manganite ceramics is a key parameter that characterizes the sensitivity of resistivity to temperature changes. However, many studies report that these materials typically exhibit a low TCR peak temperature (T_k) and limited maximum TCR values, which restricts their practical applications. Notably, the resistivity of these materials increases sharply near the metal-insulator transition temperature, T_MI leading to a significant rise in TCR. This unique behavior has been attributed to MnO₆ distortion, indicating that further research is needed to clarify the role of lattice distortion in influencing TCR. To explore this, La_0.8-xM_xNa_0.2MnO₃ (M=Eu³⁺, Dy³⁺, Er³⁺, x = 0, 0.1] monovalent-doped manganites was prepared using the solid-state reaction method, aiming to investigate how lattice distortion affects TCR. Specifically, we focused on the substitution of smaller ionic radius elements, such as Eu³⁺ (1.12 Å), Dy³⁺ (1.07 Å) and Er³⁺ (0.89 Å) compared to La³⁺ (1.216 Å). Our findings revealed that all substituted samples exhibited a metal-insulator transition with an increase in resistivity. In contrast, the parent sample exhibited metallic behavior across the entire measured temperature range of 30 K to 300 K with lower resistivity than the substituted samples. Interestingly, our results indicate that TCR values are significantly influenced by the type of elemental substitution. The maximum TCR increased from 0.83 % K^-1 at ~118 K for the x = 0 sample to 0.93 % K^-1 at ~220 K for the Dy-substituted sample, 1.012 % K^-1 at ~280 K for the Er-substituted sample and 6.21 % K^-1 at 260 K for Eu-substituted sample. These findings highlight the impact of rare earth element substitution on the transformation of manganites from a ferromagnetic metal to a paramagnetic insulator and the corresponding MnO6 octahedral distortion as well as on TCR values, making these materials promising for advanced uncooled device applications.