钼酸钆晶体铁弹相变的超声衰减和内耗

用四个频率(f=31,50,72,93MHz)超声纵波测量了钼酸钆晶体铁弹铁电相变(T_c=160.90℃)引起的超声衰减(α_s)峰。得到较准确的α_s正比f²的关系,求得T_c以上α_s的临界指数从1.52±0.12变到0.89±0.12。有渡越现象。用低频(f=1Hz和150kHz)测出了相变内耗峰,肯定其为相界面运动所引起。并求得界面运动的临界应力,从而确定了本文中测得的超声衰 关键词：

ULTRASONIC ATTENUATION AND INTERNAL FRICTION DURING FERROELASTIC TRANSFORMATION OF Gd2(MoO4)3 CRYSTAL

The critical attenuation (a_s) of longitudinal ultrasonic propagation in the vicinity of the f erroelastic-f erroelectrie transformation of GMO has been measured at frequencies (f) 31, 50, 72 and 93 MHz. The proportional relation between as and f² is established satisfactorily in so far as the shear type phase transition is concerned. In addition, the critical exponents for the attenuation is determined: ρ=1.52 for T-T_c>0.05 K and the crossover behavior is observed.Eesults are also reported on a internal friction investigation (at f=1 Hz, 150kHz) of the ferroelastic transition of GMO, which is suggested to be caused by the moving interphase boundary. The critical stress to move the boundary is determined and it is then confirmed that the mechanism of the ultrasonic attenuation of longitudinal wave in the 2-4°direction is just contributed by the fluctuation damping.