Preparation And Properties Of PIN-PHT Ternary Piezoelectric Ceramics

With the wide application of piezoelectric devices in high-temperature environments,piezoelectric ceramic materials with high piezoelectric performance and high Curie temperature have attracted great attention.In this research,a novel ternary piezoelectric ceramic Pb（In,Nb）O₃-Pb（Hf,Ti）O₃（PIN-PHT）was prepared by solid solution of ferroelectric Pb(In_1/2Nb_1/2)O₃（PIN）with a small tolerance factor and Pb Hf O₃-Pb Ti O₃（PHT）with good electrical properties.The composition of the morphotropic phase boundary was predicted through the ternary phase diagram.The piezoelectric properties and Curie temperature of the samples at morphotropic phase boundary were discussed.The influence of different components on the comprehensive properties and the mechanism of action were clarified.The temperature stability of the new system was further studied.The accurate calculation equation of the morphotropic phase boundary components of the ternary system was also constructed to provide theoretical and experimental basis for in-depth study of the preparation and modification of high-temperature piezoelectric ceramics.Further we studied on its modification by adding sintering aids and single-ion doping,and discussing their respective performance control mechanisms.The main content and conclusions were as follows:According to the linear combination rules,the morphotropic phase boundary components of PIN-PHT piezoelectric ceramics were selected.The ceramics were prepared by traditional solid-phase method,and the preparation conditions were optimized.The phase structure,dielectric properties,piezoelectric properties and Curie temperature of the ceramics were systematically studied.The results showed that the rhombohedral phase and the tetragonal phase coexisted at the morphotropic phase boundary,and the ferroelectric domains were more likely to face the direction of the external electric field,which made the degree of polarization become higher.At this time,the PIN-PHT piezoelectric ceramics also had excellent electrical properties.The best composition of the piezoelectric ceramics was 0.08Pb(In_1/2Nb_1/2)O₃-0.92Pb(Hf_0.47Ti_0.53)O₃ where the piezoelectric constant d₃₃reached 490 p C/N,the relative dielectric constantε_r was 1528,and the Curie temperature T_c reached 360°C.Compared with polycrystalline ceramics such as PZT5,the PIN-PHT system exhibited better piezoelectric performance at a similar Curie temperature,making it an ideal choice for the development of high-temperature piezoelectric ceramics.The effect of sintering aid Cu F₂ on the sintering temperature,physical and electrical properties of PIN-PHT piezoelectric ceramics was studied.The results showed that the addition of Cu F₂ greatly reduced the sintering temperature of the PIN-PHT ceramics,the optimal sintering temperature was 1100 ℃.And the optimal doping amount of Cu F₂ was0.75 at%.At this time,the optimal performance of PIN-PHT piezoelectric ceramics was d₃₃=488 p C/N,which was the same level as the pure phase obtained at the sintering temperature of 1250 ℃.In further,the other electrical properties areε_r=1630,k_p=0.6,tanδ=0.14%,T_c=348 ℃,respectively,which provide theoretical and experimental support for the good application of PIN-PHT piezoelectric ceramics.In addition,Cu F₂ doping could reduce the domain wall mobility and stabilize the domain wall,thereby increasing the mechanical quality factor Q_m to 387.The effect of different content of Bi₂O₃ on the microstructure and piezoelectric properties of the sample was studied.The results showed that the addition of Bi₂O₃ made the PIN-PHT piezoelectric ceramics obtain a good microstructure,and the change in bulk density also proved the result.As the amount of doping increases,the piezoelectric constant,dielectric coefficient and electromechanical coupling coefficient all showed a trend of first increasing and then decreasing.The prepared PIN-PHT piezoelectric ceramics showed the best electrical properties at a doping level of 1.5 at%and a sintering temperature of 1250 ℃,namely d₃₃=568 p C/N,k_p=0.63,Q_m=160,ε_r=2096.