Gaps between zeros of Dedekind zeta-functions of quadratic number   fields. II
  Let $K$ be a quadratic number field and $\zeta_K(s)$ be the associated Dedekind zeta-function. We show that there are infinitely many normalized gaps between consecutive zeros of $\zeta_K(s)$ on the critical line which are greater than $2.866$ times the average spacing. 
H. M. Bui, Winston Heap, Caroline L. Turnage-Butterbaugh
math.NT