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Phase transitions and dielectric properties of NaNbO3-based solid solutions

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 Key Laboratory of Inorganic Functional Material and Device, CAS, Shanghai Institute of Ceramics, Chinese Academy of Sciences  

中国科学院无机功能材料与器件重点实验室  

  Phase transitions and dielectric properties of NaNbO3-based solid solutions  

  Prof.  Igor Raevski 

  Southern Federal University,   

  Faculty of Physics and Research Institute of Physics  

  Rostov-on-Don, Russia  

  时间:2016年11月23日(星期三)上午09:45  

    地点: 4 号楼 14楼第二会议室  

  联系人: 曾江涛   副研究员  

          李国荣   研究员  

  欢迎各位老师同学光临!  

  NaNbO3, is an end member of several alkaline niobate-based solid solutions, such as (Na,K)NbO3 or (Na,Li)NbO3, which represent an important group of environmental-friendly, lead-free piezoceramics. Moreover, the NaNbO3-based antiferroelectric (AFE) materials were recently proposed for energy storage, high-strain actuators, and electrocaloric applications. 

  On heating from liquid helium temperature NaNbO3 exhibits a series of seven phase transitions from low temperature ferroelectric (FE) phase N (R3C) to high temperature paraelectric cubic phase U (Pm3m). In addition one more FE phase Q (Pmc21) can be induced in by application of electric field. Q phase can also appear due to size effects. The e(T) maximum is observed at 370 0C and corresponds to the transition between two AFE phases: P(Pbma) and R(Pmnm).  

  NaNbO3 -based solid solutions are usually divided into two groups. In solid solutions of the group I high temperature FE phase appears at small (a few mol.%) content x of the second component, the  e(T) maximum  temperature Tm dependence on x is rather smooth and the e(T) maxima are sharp. In solid solutions of the group II the AFE phase remains stable up to the comparatively high ( »10-50 mol.%) critical x=x0 value while at x>x0 the FE phase becomes stable which is accompanied by an abrupt drop in Tm values and dramatic increase of the e(T) maxima diffusion. Compositions with x>x0 exhibit a relaxor-like behavior. Relaxor-like behavior is also observed in some ternary NaNbO3 -based solid solution systems. 

  The effect of technological factors on phase transitions’ temperatures and diffusion as well as on dielectric properties of nominally pure NaNbO3 and NaNbO3 -based solid solutions will be discussed. 

 
 
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