铌酸锂钠在低温时的介电铁电和热电性

在300—20K的温度范围内观测了用丘克拉斯基法生长的Li_0.025Na_0.975NbO₃晶体的介电、铁电和热电特性。介电常数,极化强度和热电性的反常表示该晶体在低温时发生相变。此相变有特别大的热滞(约80K),降温时发生于180K附近,升温时发生于260K附近。测量了晶体的室温结构,指出了可能的低温相点群。观测了热电电荷的时间响应,报道了热电电荷随时间改变符号的特异现象,认为其起因是相变过程中两相共存。 关键词：

DIELECTRIC, FERROELECTRIC AND PYROELECTRIC PROPERTIES OF LITHIUM SODIUM NIOBATE AT LOW TEMPERATURES

The dielectric, ferroelectric and pyroelectric properties of Li_0.025Na_0.975NbO₃ crystals grown by the Czochralski technique have been investigated in the temperature range of 20 K to 300 K. The anomalies of the dielectric constant, electric polarization and pyroelectric properties indicate the existence of a low temperature phase transition. It occurs at about 180 K on cooling and at about 260 K on heating, wit an extraordinary large thermal hysteresis of about 80 K. The room temperature structure of the crystal has been determined and the possible point groups of the low temperature phes deduced. The time response of the pyrocle-ctric charge has been observed. A peculiar new phenomenon that the pyroelectric charge changes its polarity with time is reported. It is attributed to the coexistence of two phases in the process of phase transition.