The temperature-dependent domains,SHG effect and piezoelectric coefficient of TGS

<正>The temperature-dependent,second-order,nonlinear,optical coefficient(x（2）).piezoelectric coefficient (d33),pyroelectric coefficient（Ps） and domains on triglycine sulfate（TGS） reported herein provide a clue for us to investigate these as a typical second-order phase transition.The symmetry breaking occurrence is definitely confirmed by the temperature-dependent x（2） in which x（2） displays a limited value at the ferroelectric phase,indicating the space group（P21） chosen is correct,and when x（2） basically maintains a zero value at the paraelectric phase,indicating the space group should be centric.Interestingly,after normalization of x（2）,d33 or Ps,the change trend with temperature is basically overlapped,probably abiding by Landau theory.Moreover,temperature-dependent domains directly show the symmetry breaking occurrence.