Ferroelectric properties of lead germanate derivatives: Pb5-xMxGe3O11, m = (Cs½Bi½) and (Nd2/31/3

Abstract
The substitution of (Cs1+,Bi3+) for Pb2+ in ferroelectric Pb5-x(Cs, Bi)xGe3O11 mixed crystals lowers Tc considerably. Improved pyroelectric coefficients of 2. 310-8 C cm-2K-1 for x = 0. 2 (Tc 376 K) suggest a gain in sensitivity by using the material for pyroelectric thermal detectors. By the substitution of trivalent cations like Nd3+ (or Bi3+) vacancies (□) are formed according to Pb5-x(Nd2/31/3 xGe3O11. Although this is only possible to about x = 0. 03 even this small content lowers Tc extremely to 425 K and raises the DC resistivity to around 1015OMcm.