High Piezoelectric and Dielectric Properties of La‐Doped 0.3Pb(Zn_1/3Nb_2/3)O₃–0.7Pb(Zr_xTi_1−x)O₃ Ceramics Near Morphotropic Phase Boundary

Abstract

La‐doped 0.3Pb(Zn1/3Nb2/3)O3–0.7Pb(ZrxTi1−x)O3 (x=0.5–0.53) piezoelectric ceramics with pure perovskite phase were synthesized by a two‐step hot‐pressing route. The piezoelectric properties of various compositions near the morphotropic phase boundary (MPB) were systematically investigated. Not only was the exact MPB of this system determined via X‐ray diffractometry analysis, but also the peak of piezoelectric properties was found near the MPB. The optimum piezoelectric properties of this series were observed in the specimen with Zr/Ti=51/49. The piezoelectric coefficient (d33) and electromechanical coupling factor (kp) were 845 pC/N and 0.70, respectively, which have not been reported in this system so far. Large permittivity (ɛr=4088) and permittivity maximum (ɛm=29 500) were also obtained for the poled specimens. The temperatures (Tmax) of the permittivity maxima ranged from 206° to 213°C with various Zr/Ti ratios.

Investigation of La-doped 0.25Pb(Zn1/3Nb2/3)O3-0.75Pb(ZrxTi1-x)O3 ceramics near morphotropic phase boundary

“…8 The P-E curve and S 33 -E curve of specimen with Zr/Ti053/47 reduces the dielectric losses. This result agrees with many reports [8,16,18,19] and was explained as polarization causes domain reorientation along one direction. And as observed in some researches [18,19], the dielectric losses show an increase tendency with the increase of the Zr/Ti ratio.…”

“…And when Zr/Ti ratio is 57/43 where the rhombohedral phase exist only, the turn of 90°domains begins to dominate, so the opposite result happens. These results coincide with 0.3PZN-0.7PLZT by Guochu Deng et al [8].…”

“…2. For the first four compostions (Zr/Ti051/49, 52/48, 52.5/47.5, 53/47) , the {200} reflection clearly splits into two peaks and can be well fitted with three Gaussian peaks (dash lines), which correspond to (002) T , (200) R , and (200) T from left to right, respectively [8,13]. Though the following three specimens (Zr/Ti053.5/46.5, 54/46, 55/45) don't clearly splits into two peaks , the peak can also be well This means the tetragonal and rhombohedral phases coexist in these compostions.…”

“…Low dielectric loss (tgδ00.2%) and high mechanical quality factor (Qm01041) were achieved through MnO 2 addition [6]. On the contrary, 0.3PZN-0.7PZT system is modified as "soft" piezoelectric ceramics just because of its higher piezoelectric properties, just like La-doped 0.3PZN-0.7PZT by Guochu Deng , Xia Zeng et al [8][9][10]. Though very high piezoelectric coefficient (d 33 0 845 pC/N) and electromechanical coupling factor (k p 00.7) were attained through a two-step hot-pressing route , dielectric loss is still high (tgδ>2.0%) and the cost is huge [8].…”

“…On the contrary, 0.3PZN-0.7PZT system is modified as "soft" piezoelectric ceramics just because of its higher piezoelectric properties, just like La-doped 0.3PZN-0.7PZT by Guochu Deng , Xia Zeng et al [8][9][10]. Though very high piezoelectric coefficient (d 33 0 845 pC/N) and electromechanical coupling factor (k p 00.7) were attained through a two-step hot-pressing route , dielectric loss is still high (tgδ>2.0%) and the cost is huge [8]. The good piezoelectric properties (d 33 0580±10 pC/N) was obtained by a conventional oxide mixing oxide technique and excess ZnO addition , but dielectric loss is higher (tgδ0 3.85%) [10].…”