Research On Electrostrictive Properties Of Transparent Ferroelectric Ceramics

The deformable mirror is one of the adaptive optical modulation devices.Ceramic is used as micro actuator and glass is used as optical transmission medium.Through the deformation of ceramic,the deformation of glass can achieve optical phase compensation.At present,the deformable mirror used in our country has some disadvantages,such as complicated structure,materials aging and pre polarization required.In view of the above problems,some researchers continue to develop new materials for deformable mirrors.Lead lanthanum zirconate titanate（PLZT）ceramic is a kind of transparent ferroelectric ceramics with good electrostrictive properties.The PLZT ceramics prepared by hot pressing sintering in oxygen have good light transmittance and high refractive index,which can be used as light transmission medium.The electrostrictive strain of PLZT ceramic in low driving electric-field has met the application standards of micro actuator.Therefore,the transparent PLZT electrostrictive ceramic can be used as the key functional material of the new deformable mirror.In this paper,PLZT（9/65/35）was selected as the research object.To further optimized the electrostrictive properties of PLZT ceramic,Ba:PLZT,Bi:PLZT,Eu:PLZT and PLZST series ceramics were prepared by doping PLZT（9/65/35）with Ba²⁺,Bi³⁺,Eu³⁺and Sn⁴⁺ions.The phase structure,dielectric properties,ferroelectric properties and electrostrictive properties of Ba:PLZT,Bi:PLZT,Eu:PLZT and PLZST series ceramics were systematically studied.Ba:PLZT,Bi:PLZT,Eu:PLZT series ceramics were prepared by hot pressing sintering in oxygen.The phase structure,dielectric properties,ferroelectric properties and electrostrictive properties of PLZT（9/65/35）ceramics doped with three different ions were systematically studied.The electrostrictive coefficient(Q₃₃)and electrostrictive hysteresis level（η）of Ba:PLZT,Bi:PLZT,Eu:PLZT ceramics were calculated.The results show that the three doped ions enter the A-site of perovskite structure of ABO₃ in Ba:PLZT,Bi:PLZT,Eu:PLZT ceramics.It was found that the electrostrictive strain(S₃₃)and the electrostrictive coefficient(Q₃₃)of PLZT（9/65/35）ceramics were not significantly increased by doping of three ions,but the electrostrictive hysteresis level（η）of PLZT（9/65/35）ceramics decreased from 30.66%to 16.06%by doping of Eu³⁺ions in the a position.Sn⁴⁺ion with the same valence and close to the ion radius of Zr/Ti was selected to dope PLZT（9/65/35）ceramics.The effects of different Sn⁴⁺doping percentage on the microstructure,electrical properties,light transmittance,electrostrictive properties and electrostrictive coefficient(Q₃₃)of PLZST ceramics were studied.The internal mechanism was analyzed.It is believed that Sn⁴⁺enters the B-site of perovskite structure of ABO₃ in PLZST ceramics.All PLZST ceramic samples show good optical transmittance.With the increase of Sn⁴⁺doping（0.0wt%-0.6wt%）,the grain size and dielectric constant of PLZST ceramics decrease gradually.The ferroelectric properties of PLZST ceramics remain unchanged,while the electrostrictive strain(S₃₃)and electrostrictive coefficient(Q₃₃)increase gradually.The results show that the electrostrictive coefficient(Q₃₃)of PLZST ceramics has little effect on the ferroelectric phase and antiferroelectric phase,and is mainly affected by the arrangement of B-site composite ions,which is consistent with the click space theory.When the content of SnO₂ is 0.6wt%,the electrostrictive strain(S₃₃)and electrostrictive coefficient(Q₃₃)of PLZST ceramics are 0.29%and 0.027m⁴/c²,respectively,which are slightly higher than those of undoped PLZT ceramics（9/65/35）(the electrostrictive strain(S₃₃)is 0.26%,and the electrostrictive coefficient(Q₃₃)is 0.024m⁴/C²).