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Pulsed laser deposition (PLD) method was used for the preparation of epitaxially grown Pb ([Mg.sub.1/3][Nb.sub.2/3])[O.sub.3]-PbTi[O.sub.3] (PMN-PT) thin films on appropriate buffer layers deposited on a Si substrate. Findings reveal high crystallinity of PMN-PT film with full width at half maximum = 0.73 deg and 1.6 m thickness.

The nature of the symmetry changes associated with phase transitions in stibnite, [Sb.sub.2][S.sub.3], has been investigated by powder and single crystal X-ray diffraction. Above 420 K stibnite (I) is centrosymmetric Pbnm. Stibnite (II) is stable between 290 and 420 K and is acentric [P2.sub.1]nm. Below 290 K stibnite (III) is stable and systematic absences indicates that this phase is monoclinic with space group [P2.sub.1] or Pm, or triclinic P1, but the cell dimensions remain geometrically orthorhombic. These findings are in agreement with variations in physical and electrical properties reported in the literature.

Structural phase transition of trigadolinium ruthenium heptaoxide, [Gd.sub.3]Ru[O.sub.7] is reported. The crystals of the complex undergo a reversible transition which is structurally characterized by an additional tilt.

Structural evolution of a La2Ti2O7 ferroelectric compound possessing perovskite‐type slabs at elevated temperatures was investigated using the single‐crystal X‐ray diffraction technique. The monoclinic low‐temperature phase (L) transformed into the orthorhombic high‐temperature phase (H) via an incommensurately modulated phase (IC) between ∼989 and ∼1080 K. The L–IC transition was considered to be of the first order, with the L+IC two‐phase co‐existing region between ∼989 and ∼1027 K. The structure of IC was determined from the (3+1)‐dimensional superspace representation with a modulation vector q = αao (α ≃ 0.49), where ao is the a‐axis vector of the basic cell. The structural modulation originated from the variation of the tilt angle of the TiO6 octahedra in the perovskite‐type slab in association with small positional displacements of La atoms. The IC–H transition took place at ∼1080 K and was close to the second order. During the IC–H transition, nanoscale flat plate domains having either a cell twin of the L‐type structural modules or a cell twin of the alternating H‐ and L‐type structural modules began to appear in the approximant structure of IC. The thickness of the flat plate domains then grew rapidly along the modulation vector in proportion to (½ − α)−1 as α approached ½ with decreasing temperature. In the two‐phase L+IC co‐existing region, the IC phase consisting of the two types of cell twins was gradually replaced with the low‐temperature monoclinic phase L, which is not cell twinned but rather twinned macroscopically by the L‐type structural modules. Crystals of La2Ti2O7 undergo successive phase transitions between the low‐temperature monoclinic phase and the high‐temperature orthorhombic phase with an intermediate incommensurately modulated phase at around 1000 K. [ABSTRACT FROM AUTHOR]