Lead-free KNN-based ceramics with enhanced pyroelectric properties and good temperature stability via constructing phase boundary

Abstract

In this work, the influence of Li and BiFeO₃ (BF) doping based on potassium sodium niobate (KNN) on the pyroelectric properties of the ceramics was investigated. To achieve two-phase coexistence at room temperature, (K_0.5Na_0.5)_0.95Li_0.05NbO₃(KNLN) ceramic with a high Curie temperature was selected for doping while BF(BiFeO₃) with high ferroelectricity, spontaneous polarization, and good temperature stability was chosen as a variable dopant. By establishing the coexistence of O and T phase at room temperature, the energy barrier for polarization reversal is diminished, thereby enhancing the sensitivity of polarization intensity variations with temperature, ultimately leading to an enhancement in their pyroelectric properties. Consequently, (1-x)KNLN-xBF (x = 0.5 %) exhibited a large pyroelectric coefficient p (471 μC/m²/K) along with excellent figure of merits (FOMs) at room temperature: F_i = 1.94 × 10⁻¹⁰ m V⁻¹, F_v = 0.031 m² C⁻¹, F_d = 1.49 × 10⁻⁵ Pa^−1/2, with a high Curie temperature (441℃). Moreover, this component also exhibited good temperature stability, the pyroelectric coefficient could reach 387 μC/m²/K after annealing at 200℃ for an hour, which provides a promising KNN-based materials with commercial value for application of pyroelectric infrared radiation detector (PIRD).