Electrocaloric Effects And Temperature-Dependent Photoluminescence Of Er³⁺ Doped Bismuth Sodium Titanate Based Ceramics

The refrigeration technology using electrocaloric effects of polar materials has attracted more and more attention of the industry because of the advantages of simple design and flexible application.Sodium bismuth titanate(Bi_0.5Na_0.5Ti O₃,abb-reviated as BNT)based ceramics exhibit excellent properties in the morphotropic phase boundary（MPB）.On the other hand,rare earth doped piezoelectric ceramics which are expected to integrate multiple properties at the same time are widely con-cerned.In this paper,Er³⁺doped BNT-based ceramics were prepared to study the promote on electrocaloric effects and the luminescent temperature characteristics.The main contents are as follows:1.Er³⁺doped 0.956Bi_0.5-xNa_0.5Ti O₃-0.044Ba(Mg_1/3Nb_2/3)O₃（956BNT-44BMN）,0.96Bi_0.5-xNa_0.5Ti O₃-0.04Sr(Mg_1/3Nb_2/3)O₃（96BNT-4SMN）and 0.978Bi_0.5-xNa_0.5Ti O₃-0.022Ca(Mg_1/3Nb_2/3)O₃（978BNT-22CMN）was prepared.Compared with others,956BNT-44BMN:x Er have maximum polarization intensities of 57.486μC/cm² in ferroelectric test,and get the maximum electrocaloric temperature changes of 2.65K in electrocaloric effects test,In the optical performance test among them,green light emission appeared and optical temperature sensitivity coefficients of 0.0053K^-1were obtained at 569K.Compared with other rare earth doped multi-component systems,956BNT-44BMN:x Er showed superior properties,which Due to the different A-position of the modifier in the solid solution.2.Er³⁺doped 0.93Bi_0.5Na_0.5Ti O₃-0.07Ba Ti O₃（93BNT-7BT）was used to observe the changes of its electrocaloric effects performance,luminous performance and optical sensitivity,and to find out the doping concentration which can really improve the performance.The results show that Er³⁺doped 93BNT-7BT has a maximum polarization intensity of 58.086μC/cm² in ferroelectric test,and a maximum electro-caloric temperature change of 2.19K in electrocaloric effects test.In optical per-formance test,the optical temperature sensitivity coefficient of 0.0036K^-1 is obtained for x=0.6wt%sample at 542K.and 93BNT-7BT-0.6Er₂O₃ shows good performance,which has a good practical prospect.3.The 0.885Bi_0.5Na_0.5Ti O₃-0.06Ba Ti O₃-0.55(Sr_0.7Bi_0.18Er_0.02□_0.1)Ti O₃（BNBT6-0.055SBET）sample was prepared according to the formed research,and its structure and performance were further studied.Meanwhile,the 0.9Bi_0.5Na_0.5Ti O₃-0.06Ba Ti O₃-0.04Sr_0.7Bi_0.18-xEr_0.02Yb_xTi O₃（BNBT6-4SBET:x Yb）has been designed and prepared,and the changes of electrocaloric effects of the system at different tem-peratures are systematically studied.BNBT6-0.055SBET and BNBT6-4SBET:x Yb are the two systems with the maximum polarization intensity of 35.143μC/cm² and36.279μC/cm² respectively in ferroelectric test.The two kinds of samples have obvious negative electrocaloric effects,with the largest adiabatic reversible tem-perature change of 3.27K and 3.24K respectively in the electrocaloric effects test.Compared with BNBT6-4SBET:x Yb,BNBT6-0.055SBET has better per-formance and is of great significance in the development of multifunctional piezo-electric ceramics.This shows that the component is very promising to be used in act-uators and temperature sensing equipment.