Study On The Preparation And Improved Properties Of PHT-PNN Ternary Piezoelectric Ceramics

Due to the high integration,small size,excellent piezoelectric and dielectric properties,low temperature co-fired multilayer piezoelectric ceramics were widely used in the field of integrated circuits.Therefore,it is critical to find an appropriate piezoelectric ceramic with excellent electrical properties sintered at a low temperature.Recent research demonstrated that Pb（Hf,Ti）O₃-Pb（Ni,Nb）O₃（PHT-PNN）was a promising ceramic system with ultra-high piezoelectric and dielectric properties.However,its high sintering temperature（1250℃）limits its application in the filed of low temperature co-fired multilayer piezoelectric ceramics.In this work,0.51Pb(Hf_0.3Ti_0.7)O₃-0.49Pb(Ni_1/3Nb_2/3)O₃piezoceramics were synthesized by a conventional solid-state sintering route,and the electrical properties of the ceramics were improved while the sintering temperature was reduced by means of ions-pair doping,sintering aids,and ions co-doping.The main conclusions are as follows.The equimolar Li⁺and Bi³⁺co-doped 0.51Pb(Hf_0.3Ti_0.7)O₃-0.49Pb(Ni_1/3Nb_2/3)O₃piezoceramics were fabricated by a conventional solid-state reaction route and the effects of Li⁺-Bi³⁺co-doping on crystalline structure,morphological structure,piezoelectric and dielectric properties of PHT-PNN ceramics were systematically analyzed.Results revealed that Li⁺and Bi³⁺could enter the PHT-PNN lattice,distorting the unit-cell,and improving the electrical performance of the materials.The liquid phase formed by Li₂CO₃ and Bi₂O₃during the sintering process promoted the ceramics homogeneous growth of grains and densification.It was found that PHT-PNN/1.0 mol%(Li⁺-Bi³⁺)ceramics sintered at 1100℃had excellent electrical properties,i.e.d₃₃=1025 p C/N,ε_r=7974,k_p=0.65,tanδ=2.9%and T_c=119℃.The CuO doped 0.51Pb(Hf_0.3Ti_0.7)O₃-0.49Pb(Ni_1/3Nb_2/3)O₃ piezoceramics were manufactured using a conventional mixed oxide route and the effects of C u O on sintering temperature,microstructureandelectricalpropertiesof0.51Pb(Hf_0.3Ti_0.7)O₃-0.49Pb(Ni_1/3Nb_2/3)O₃ piezoelectric ceramics were systematically investigated.Results showed that PHT-PNN/CuO piezoelectric ceramics had excellent low-temperature sintering characteristics,which could be densely sintered at 1050℃.This is mainly due to the liquid phase formed by CuO and Pb O at 790℃,which can facilitate the sample quickly dense and obtain uniform microstructure.The measurement of electrical properties showed that the sample with 0.5 mol%C u O exhibited excellent piezoelectric and dielectric characteristics,i.e.d₃₃=912 p C/N,ε_r=6665,k_p=0.55,tanδ=2.73%and T_c=130℃.The Li⁺,Bi³⁺and Cu²⁺co-doped 0.51Pb(Hf_0.3Ti_0.7)O₃-0.49Pb(Ni_1/3Nb_2/3)O₃piezoelectric ceramics were investigated.Results showed that PHT-PNN/Li⁺-Bi³⁺/C u²⁺ceramics could form homogeneous and dense microstructure at the sintering temperature below 1000℃.The dielectric and piezoelectric properties of PHT-PNN piezoceramics sintered at low temperature were greatly enhanced by the addition of Li⁺,Bi³⁺and C u²⁺.The optimum properties,i.e.d₃₃=1000 p C/N,ε_r=7248,tanδ=2.99%and T_c=119℃were obtained for the sample with 1.0 mol%(Li⁺-Bi³⁺)and 0.5 mol%Cu²⁺,when sintered at1000℃for 2h.