Ferroelectric ceramics of 2(Pb,Sr)Nb2O6 :(K,Na)NbO3 tungsten bronze morphotropic phase boundary system

Systematic study of the chemistry-structure-property relation in alpha(Pb1- xSrx)Nb(2)O6:beta(K1-yNay)NbO3 oxide system has been carried out for alpha: beta = 2:1 and x = y. The experimental work is focused around compositions near the potential morphotropic phase boundary (MPB) that separates the fer roelectric orthorhombic (m2m) and ferroelectric pseudo-tetragonal phase (mm 2). Ceramics of various compositions are prepared by solid state route and characterized for crystallographic phases and phase transitions using X-ray diffraction and thermal expansion measurements. Dielectric properties of t hese compositions as a function of temperature and frequency are studied. X RD analysis indicates the coexistence of pseudo-tetragonal and orthorhombic phases near x = 0.295. The dielectric permittivity reaches a maximum and p hase transition temperature reaches a minimum near this composition.