New high-performance ferroelectric solid solutions based on Pb(Zr1-xTix)O-3 (PZT), which are doped with cryolite-type strontium niobate (SNO, Sr-4(Sr2-2y/3Nb2+2y/3)O11+yVO;1-y with 0 <= y <= 1) and hence denoted PZT:SNO, and their microscopic structure and defect chemistry are described. Extended X-ray absorption fine-structure (EXAFS) analyses of PZT:SNO samples revealed that similar to 10% of Sr2+ occupy the nominal B-sites of the perovskite-type PZT host lattice. This result is supported by EXAFS analyses of both a canonical SrTiO3 perovskite and two SNO model and reference compounds. Fit models that do not account for Sr2+ on B-sites are ruled out. A clear Sr-Pb peak in Fourier-transformed EXAFS data visually confirms this structural model. The generation of temporary oxygen vacancies and the intricate defect chemistry induced by SNO-doping of PZT are crucial for the exceptional material properties of PZT:SNO. As a result, ferroelectric PZT:SNO solid solutions are very attractive for use in new and innovative piezoelectric actuator and transducer applications.