Study on Effect of Al2O3 Doping on Microstructure and Properties of LiNbO3 Piezoelectric Ceramics
Lithium niobate(LiNbO3,LN)piezoelectric ceramics were prepared by vacuum hot-pressing sin-tering at 900 C and 35 MPa for 120 min.The effects of different Al2O3 doping amounts on their piezoelec-tric properties were studied.Through the analysis of phase,density,microstructure,piezoelectric and dielec-tric properties,it is found that within the range of Al2O3 doping amounts of 0.5％～3％(molar fraction),all LN piezoelectric ceramics samples exhibit the same position of main diffraction peaks that are sharp and indicative of a perovskite-type structure.with the increase of Al2O3 doping amount,the particle size of LN piezoelectric ceramics gradually decreases while the porosity increases both in size and quantity.In addi-tion,the density and piezoelectric constant d33 increase at first and then decrease,reaching their maximum of 4.65 g/cm3 and 11.3 pC/N,respectively,at an Al2O3 doping amount of 1％.The above piezoelectric con-stant is 88.3％higher than that of LN piezoelectric ceramics prepared by laser sintering.At the test fre-quency of 1 MHz,the relative dielectric constant of LN piezoelectric ceramics increases gradually with the increase of Al2O3 doping amount.
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