(Sr0.7Bi0.2)TiO3取代BNT基无铅陶瓷的相变及储能特性

采用弛豫铁电体(Sr0.7Bi0.2)TiO3与铁电体(Bi0.5Na0.5)TiO3构建了的新型二元系BNT基无铅陶瓷材料:(1-x)(Bi0.5Na0.5)TiO3-x(Sr0.7Bi0.2)TiO3(记为BNT-xSBT,x=10mol;、20mol;、30mol;和40mol;).通过传统固相法进行制备,研究了(Sr0.7 Bi0.2)TiO3取代对其结构、相变、铁电性能和储能特性的影响.结果表明,室温所测BNT-xSBT陶瓷为准立方结构;介温和铁电性则证实其为极性三方和非极性四方共存相结构.A位复合占位的BNT-xSBT陶瓷是典型的弛豫铁电体,其Tm随x的增大而减小.低温(Td)处的介电反常源于结构(三方和四方)起伏所引起的缓慢转变过程.(Sr0.7 Bi0.2)TiO3取代量增大时,其Td降低,四方相增多,并伴随非极性微区增长;并导致BNT-xSBT陶瓷的铁电性减弱和电滞回线变形.x=30mol;时,BNT-xSBT陶瓷具有大的Pmax=26.8μC/cm2、小的Pr=1.4μC/cm2,和较好的储能特性:W=0.74 J/cm3,η=68.5;(@70 kV/cm).

Phase Transition and Energy-storage Property of ( Sr0.7Bi0.2 ) TiO3 Substituted BNT-based Lead-free Ceramics

Innovative binary BNT-based lead-free ceramics which is composed by (Sr0.7Bi0.2)TiO3 relaxor ferroelectric and (Bi0.5Na0.5)TiO3 ferroelectric, (1-x)(Bi0.5Na0.5)TiO3-x(Sr0.7Bi0.2)TiO3(BNT-xSBT for short, x=10mol%, 20mol%, 30mol% and 40mol%) was designed.All the BNT-xSBT ceramics were fabricated by the traditional solid-state processing route , and the effect of ( Sr0.7 Bi0.2 ) TiO3 on the structure , phase transition , ferroelectric property and energy-storage property of BNT-xSBT ceramics was investigated .The results show that BNT-xSBT ceramics exhibit pseudo-cubic phase at room temperature , and coexistence phase structure of polar rhombohedral ( R3c) and non-polar tetragonal ( P4bm) for BNT-xSBT ceramics was identified by dielectric and ferroelectric property .BNT-xSBT ceramics with co-occupied in A-site are relaxor ferroelectric, and Tm decreases with increasing of (Sr0.7Bi0.2)TiO3 content. The dielectric abnormal peak at low temperature ( Td ) derives from a slow transition which is caused by structure (rhombohedral and tetragonal) fluctuation.With increasing of (Sr0.7Bi0.2)TiO3 content, Td of BNT-xSBT ceramics decreases , tetragonal phase and non-polar nano-regions increases , resulting in weak ferroelectric property and distorted ferroelectric hysteresis loop .For x =30mol%, BNT-xSBT ceramics show a large Pmax =26.8 μC/cm2 , a small Pr =1.4 μC/cm2 , good energy storage density W=0.74 J/cm3 and energy storage efficiency η=68.5%(@70 kV/cm).