The results obtained in the study of (K0.44 Na0.52 Li0.04)0.97 La0.01Nb0.9Ta0.103 ceramics obtained by solid state sintering from the precursor NaNbO3 synthetized by the reactive templated grain growth (RTGG) technique are presented. X-ray diffraction studies show the coexistence of two crystal phases, orthorhombic and tetragonal, the last one being the more abundant. Dielectric measurements evince the effect of La doping through a decrease in the transition temperatures with respect to those reported for undoped KNN (tetragonal-cubic TT-C= 264 o C and orthorhombic -tetragonal TO-T = 90 oC, in our case). The maximum value for the dielectric permittivity is surprisingly high at 6800 at room temperature and 1 kHz. Ferroelectric hysteresis measurements performed at room temperature give Pr = 20 μC/cm2 for the remnant polarization and Ec = 9 kV/cm for the coercive field. Piezoforce microscopy (PFM) shows domain switching areas in response to the applied electric field but also non-switching zones where the polarization is either perpendicular to the applied field or non-existent. The hysteresis loop obtained by PFM gives a piezoelectric coefficient d31 = 164 pC.N-1 comparable to the best published values of PZT and KNN ceramics.
Financial support from CoNaCyT, Grants No. 282778 and 280309 and PAPIIT-DGAPA-UNAM Grants No. IN105307 and IN110315 is acknowledged. Technical support from I. García, I .Gradilla, E. Aparicio, E. Murillo, is greatly appreciated.