Order-Disorder Phase Transition and Dielectric Mechanism in Relaxor Ferroelectrics

IntroductionSince Pb(Mg1/ 3Nb2 / 3) O3(PMN) was first syn-thesized by Smolenski and Agranovuskaya in thelate1 950 s[1] ,a series of relaxor ferroelectrics withcomplex perovskite structure whose dielectric andferroelectric properties are rather different fromthose of normal ferroelectrics have been studied.For the lead- based relaxor ferroelectrics,thedielectric permittivity is unusually high,thesintering temperature is rather low,and thetemperature coefficient of capacitance is quitesmall,w…     

平面尺寸链公差计算的简便方法

应用多元函数的偏微分理论和工艺尺寸链原理，提出一种简化平面尺寸链公差计算的方法，应用此方法可以简捷地计算平面孔系尺寸公差及平面尺寸链中的其它尺寸公差。     

计量器具检定周期探析

根据计量器具的检定周期受其使用频率程度、使用环境、使用性能、使用准确度要求，保养，存放状况等因素的影响，进一步探讨了评定合理的计量器具检定周期的方法。