铁电晶体Pb_xBa_(1-x)Nb_2O_6和掺Li,Na的Pb_xBa_(1-x)Nb_2O_6的结构和电弹张量的测定

DETERMINATION OF STRUCTURE AND DIELETRIC, ELASTIC AND PIEZOELECTRIC COEFFICIENTS IN FERROELECTRIC SINGLE CRYSTALS Pb_xBa_(1-x)Nb_2O_6 AND Li, Na-DOPED Pb_xBa_(1-x)Bb_2O6

用提拉法从熔体中生长出Pb_(0.37)Ba_(0.63)Nb_2O_6和Pb_(0.30)Ba_(0.533)Na_(0.306)Li_(0.028)Nb_2O_6 两种铁电单晶。用X射线衍射方法分析了两种单晶的结构,结果表明,室温时两种晶体都属于四方晶系点群4mm。测定晶格参数得PBN晶体的a=12.493A和c=3.98A;掺Li,Na的PBN晶体的a=12.493A和c=3.970A。测定了两种晶体全部各52个电弹张量的分量,结果表明PBN晶体具有优良的压电性,其中压电系数d_15=108×10^(-12)C/N。这种晶体很有希望用作与厚度切变模式有关的压电换能器材料。掺Li,Na的PBN晶体的介电常数显著降低,而铁电居里点有明显的提高。

Two ferroelectric single crystals Pb0.37 Ba0.63 Nb2O6 and Pbo.30 Ba0.533 Na0.306 Li0.028 Nb2O6,pulled from melt by Czochralski technique, have been studied. By X-ray diffraction, it has been determined that both of two crystals belong to the tetragonal system with lattice parameters α = 12.493 A, c = 3.984 A for PBN, and a = 12.493 A, c-3.970 A for Li, Na-doped PBN. All of the dielectric, elastic, and piezoelectric coefficients of the two crystals have been measured. The results show that PBN crystal possesses good piezoelectric character with d15≈108× 10-12 C/N. This crystal could be a promising material for piezoelectric transducers operating in the shear mode. The dielectric constants are reduced, while the Tc is enhanced obviously in PBN doped by Li and Na Ions.