Electric field-induced strain enhancement in Pb-free Na0.46Bi0.47La0.01Ba0.05TiO< sub>3 ceramics modified by (Al0.50Nb0.50)<SUP>4+</SUP> complex ions

초록

Fast-response and high-precision electrostrain actuators, valued for their significant electric field-induced strain at high fields, are widely used in electrical and electronic devices. However, ferroelectric materials, characterized by their butterfly-shaped strain-electric field loops, can only utilize a fraction of their achievable strain due to irreversible domain reorientation which results in negative strain. In contrast, relaxor materials exhibit negligible negative strain and are distinguished by a distinctive sprout-like loop shape. Herein, a Pb-free Na0.46Bi0.47La0.01Ba0.05Ti1-x(Al0.50Nb0.50)(x)O-3 system was designed and synthesized using conventional ball milling and sintering techniques. The incorporation of (Al0.50Nb0.50)(4+) ions into the Na0.46Bi0.47La0.01Ba0.05TiO3 lattice inhibited grain growth and enhanced ergodicity. Consequently, the specimen with x = 0.035 achieved a high bipolar strain of similar to 0.42 % with an induced strain coefficient (d(33)*) of 525 pm/V at the boundary between R3c and P4bm phases, exhibiting ergodic relaxor characteristics. Pinched ferroelectric loops and reduced remnant polarization further demonstrated relaxor features for specimens with x >= 0.035. The specimen with x = 0.035 displayed moderate strain (ranging from similar to 0.32 % to similar to 0.10 %) across a broad temperature range (from 25 to 180 degrees C) under a 70 kV/cm field. Additionally, it demonstrated excellent fatigue resistance in both ferroelectric loop and bipolar strain versus electric field measurements, confirming its long-term cycle performance. This work suggests a novel design strategy for achieving high electro-strain, substantial thermal stability, and fatigue-free properties, making it well-suited for applications requiring reliable high electrostrain.

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