The influence of dopant concentration on PZT (54/46) systems doped with lanthanum and/or niobium is studied. The sintering kinetics is presented for 1 wt% of the dopant used to find the main mechanism which drives thi...The influence of dopant concentration on PZT (54/46) systems doped with lanthanum and/or niobium is studied. The sintering kinetics is presented for 1 wt% of the dopant used to find the main mechanism which drives this process. The results were compared with a phenomenological model for viscous sintering and solid state sintering. The exponent obtained for viscous sintering in PZTN, PLZT and PLZTN were 0.05, 0.01, and 0.23 respectively, which indicate that the process is reactive liquid in all cases. In the other hand, the exponent obtained for solid state sintering were 6.61, 5.68, and 1.23 respectively, and prevalence Ost-wald ripening and coalescence process together. Both dopants inhibit the grain growth and accelerate the sintering process, which increases with dopant concentration and the combination of both dopants. Shoro-hod-Olevsky model was applied for explain grain growth evolution, but does not coincide strictly with the applied model, which suggest that the process is very complex.展开更多
Pure Ko.sNao sNbO3(KNN)and KNN doped with Lit(6%mole),Lat(1.66%,5%,6%mole),and Ti+t(10%mole)were prepared by mixture of oxides using high-energy milling and conventional solid-state reaction.The effects of the dopant ...Pure Ko.sNao sNbO3(KNN)and KNN doped with Lit(6%mole),Lat(1.66%,5%,6%mole),and Ti+t(10%mole)were prepared by mixture of oxides using high-energy milling and conventional solid-state reaction.The effects of the dopant on the physical properties of pure KNN have been evaluated based on the structural,ferroelectric,pyroelectric,and dielectric measurements.The XRD measurements show that KNN pure sample contains a mixture of monoclinic and orthorhombic crystalline phases,with a slightly higher concentration of monoclinic phase.In contrast,all doped samples show a higher concentration of the orthorhombic phase,as well as the presence of a secondary phase(K6Nb10.8O3o),also detected by Raman measurements.The samples with a higher concentration of this secondary phase,also present greater dielectric losses and lower values of remnant polarization.The dielectric measurements allowed us to detect temperatures of structural transitions(orthorhombic-tetragonal,O-T)previous to the ferroelectric paraelectric transition(tetragonal-cubic,T-C),and also in this set of samples,a direct correlation was found between the values of remnant polarization and the corresponding pyroelectric signal response.展开更多
In this work,the results of the study on the optical properties of the perovskite structure ABO3 with La^(3+) substitution for ions K^(+) and Na^(+) in the A site and Ti^(4+) substitution for ion Nb^(5+) in the B site...In this work,the results of the study on the optical properties of the perovskite structure ABO3 with La^(3+) substitution for ions K^(+) and Na^(+) in the A site and Ti^(4+) substitution for ion Nb^(5+) in the B site are presented.The ceramics were sintered at 1100℃ and 1190℃ and formed at 10 MPa and 80 MPa.Dense ceramics were obtained with 94% of the theoretical density.The piezoresponse force microscopy(PFM)showed needle-shaped grains with a size of 30 nm for the samples formed at 10 MPa at both sintering temperatures.Apparently,the high temperature and high pressure used in formation reduced the energy of the band gap(Eg)from 3.36 to 3.09 eV.Strong emissions to 2.19,1.86,2.5,and 2.31 eV were obtained by exciting the samples at 325,373,457,and 500 nm,respectively;these emissions corresponded to blue-yellow-red regions of the visible spectrum.展开更多
文摘The influence of dopant concentration on PZT (54/46) systems doped with lanthanum and/or niobium is studied. The sintering kinetics is presented for 1 wt% of the dopant used to find the main mechanism which drives this process. The results were compared with a phenomenological model for viscous sintering and solid state sintering. The exponent obtained for viscous sintering in PZTN, PLZT and PLZTN were 0.05, 0.01, and 0.23 respectively, which indicate that the process is reactive liquid in all cases. In the other hand, the exponent obtained for solid state sintering were 6.61, 5.68, and 1.23 respectively, and prevalence Ost-wald ripening and coalescence process together. Both dopants inhibit the grain growth and accelerate the sintering process, which increases with dopant concentration and the combination of both dopants. Shoro-hod-Olevsky model was applied for explain grain growth evolution, but does not coincide strictly with the applied model, which suggest that the process is very complex.
基金The authors express their thanks to CONACYT for funding this research through projects CB-240460 and LN-295261,and to LIDTRA for the facilities in the use of experimental infrastructure.
文摘Pure Ko.sNao sNbO3(KNN)and KNN doped with Lit(6%mole),Lat(1.66%,5%,6%mole),and Ti+t(10%mole)were prepared by mixture of oxides using high-energy milling and conventional solid-state reaction.The effects of the dopant on the physical properties of pure KNN have been evaluated based on the structural,ferroelectric,pyroelectric,and dielectric measurements.The XRD measurements show that KNN pure sample contains a mixture of monoclinic and orthorhombic crystalline phases,with a slightly higher concentration of monoclinic phase.In contrast,all doped samples show a higher concentration of the orthorhombic phase,as well as the presence of a secondary phase(K6Nb10.8O3o),also detected by Raman measurements.The samples with a higher concentration of this secondary phase,also present greater dielectric losses and lower values of remnant polarization.The dielectric measurements allowed us to detect temperatures of structural transitions(orthorhombic-tetragonal,O-T)previous to the ferroelectric paraelectric transition(tetragonal-cubic,T-C),and also in this set of samples,a direct correlation was found between the values of remnant polarization and the corresponding pyroelectric signal response.
文摘In this work,the results of the study on the optical properties of the perovskite structure ABO3 with La^(3+) substitution for ions K^(+) and Na^(+) in the A site and Ti^(4+) substitution for ion Nb^(5+) in the B site are presented.The ceramics were sintered at 1100℃ and 1190℃ and formed at 10 MPa and 80 MPa.Dense ceramics were obtained with 94% of the theoretical density.The piezoresponse force microscopy(PFM)showed needle-shaped grains with a size of 30 nm for the samples formed at 10 MPa at both sintering temperatures.Apparently,the high temperature and high pressure used in formation reduced the energy of the band gap(Eg)from 3.36 to 3.09 eV.Strong emissions to 2.19,1.86,2.5,and 2.31 eV were obtained by exciting the samples at 325,373,457,and 500 nm,respectively;these emissions corresponded to blue-yellow-red regions of the visible spectrum.
