机构地区: 中山大学物理科学与工程技术学院物理系
出 处: 《中山大学学报(自然科学版)》 1996年第4期1-6,共6页
摘 要: 提出了凝聚态电介质中的空间电荷扩散模型,用来解释慢极化效应.对自由弛豫过程中的扩散方程,用分离变数方法求出了精确的级数解.当时间t甚小于响应时间τ时,精确解给出的衰减函数为exp(-t/τ),与经验公式一致.但当t较大时精确的衰减函数过渡到指数形式,近似的理论衰减函数可表示为exp(-t/τ+at2/τ2);当t<2.5τ时它的近似程度很好.理论给出a=3.61352.在室温下对石蜡作了仔细测量,结果和理论完全一致.当t≥2.5τ时,衰减函数已减小至不超过0.67%; A diffusion model of space charges in condensed dielectrics is used to explain the slow polarization effect. By separation of variables the diffusion equation is solved in a series form. When the time t is much smaller than the response time, the solution leads to a decay function exp( -t/τ ), which is in agreement with the empirical formula. But for larger t ,the decay function transforms into exponential form. A theoretical decay function is given as exp(- t/τ+at 2/τ 2) for t<2 5τ with a=3 613 52. When t≥2 5τ , the decay function is smaller than 0 67%, it is hardly to detect in measurement. A careful experiment for paraffin in room temperature shows that this is an excellent approximate formula.