Significant enhancement of the negative electrocaloric effect in Mn-doped PbHfO3 films

With the rapid development of artificial intelligence, the demand for refrigeration in large-scale integrated circuits is steadily increasing. The electrocaloric effect (ECE), recognized as a core mechanism of emerging solid-state refrigeration technologies, has garnered significant attention. In this study, Pb_1-xMn_xHfO₃ (PMH-100x) films with a high negative electrocaloric effect (NECE) were fabricated. Further research reveals that the enhancement of the NECE in PMH-100x films results from the incorporation of Mn²⁺ into PbHfO₃ (PHO). Mn²⁺ doping obviously improves the antiferroelectric-ferroelectric (AFE-FE) phase transition behavior, leading to the enhanced NECE performance. Experimental findings indicate that the PHO film with a Mn²⁺ doping concentration of 0.5 % exhibits the highest NECE performance. In PMH-0.5 film, it achieves ΔS = 15.1 J K⁻¹ kg⁻¹ and ΔT = −18.8 K at 60 °C under 533 kV/cm, representing a 33.3 % improvement compared to the pure PMH-0.0 sample. Furthermore, it was demonstrated that varying Mn²⁺ doping concentrations induces a transition from NECE to positive electrocaloric effects (PECE) in the samples. For instance, high PECE were observed in PMH-1.0 and PMH-2.0 films, with corresponding ΔT values of 9.4 K and 15.5 K, respectively. This transformation has considerable practical implications for refrigeration technologies that combine NECE and PECE. The present research provides a promising candidate material for solid-state refrigeration in integrated circuits.