Heather Kukkee HBSc thesis abstract

Perovskite-type compounds in the series tausonite-lueshite, (SrTiO₃-NaNbO₃), were synthesized by solid-state reaction and analyzed using X-ray powder diffractometry.  The structures of several intermediate compositions were determined using the Rietveld refinement method.  In the compositional range 0≤ x ≤0.2, the series consists of an undistorted cubic structure in the space group Pm3m, with cell dimensions ranging from a≈3.905-3.916....  At the composition of x=0.9, a combination of the orthorhombic spaces groups Pbma and Pbnm is believed to occur (a ≈ 5.558, b ≈ 15.625, c ≈ 5.519 ...).  In the compositional range 0.95≤ x ≤1.00, the structure is orthorhombic and belongs to the space group Pbma.  In the series (SrTiO₃-NaNbO₃), the degree of structural distortion increases with x as a result of Na substituting into the A-site for Sr, and Nb substituting into the B-site for Ti.