Let Sk=Fq[u(1),u(2), ....,uk]/< u(i)(3)=u(i),u(i)u(j)=u(j)u(i)=0 >, where 1 <= i,j <= k, q=pm, p is an odd prime. First, we define two new Gray maps phi and phi k, and study their Gray images. Further, we determine the structure of constacyclic codes and their dual codes, and give a necessary and sufficient conditions of constacyclic codes to contain their duals. Finally, we obtain some new quantum codes over Fq by using CSS construction, and compare the constructed codes better than the existing literature.