We present the results of a plane wave based density functional study of the structure and properties of tetragonal zirconia in the range of pressures from 0 to 50 GPa. We predict a transition to a fluorite-type cubic structure at 37 GPa which is likely to be of a soft mode origin and is accompanied by a power law decrease of the frequency of the Raman-active A(1g) mode. A detailed study of the...

First-principles calculations were performed to study the extremely tetragonal ferroelectric material Bi Zn1/2Ti1/2 O3 BZT . In agreement with experiment, we find that BZT displays extremely large cation displacements and tetragonality. Despite its high tetragonality and polarization, the local structure of the material exhibits a high degree of local disorder which is more typical of the solid...

Monolithic macroporous zirconia (ZrO2) derived from ionic precursors has been successfully fabricated via the epoxide-mediated sol-gel route accompanied by phase separation in the presence of propylene oxide (PO) and poly(ethylene oxide) (PEO). The addition of PO used as an acid scavenger mediates the gelation, whereas PEO enhances the polymerization-induced phase separation. The appropriate ch...

The surface morphology and crystal structure change of dental zirconia after hydrofluoric acid (HF) etching were evaluated. Four groups of sintered zirconia specimens were 1) control group, 2) immersion in 9.5%HF at 25°C for 1, 2, 3, or 24 h, 3) immersion in 9.5%HF at 80°C for 1, 3, 5, or 30 min and 4) immersion in 48%HF at 25°C for 30 or 60 min. The specimens were evaluated under SEM and XRD. ...

The opportunity of the Zn12xMnxGa2Se4 (0<x<1) series for exploring the possibilities of orderingdisordering processes as a function of x is shown. A pumping of Mn ions from one particular site of the crystal lattice to another occurs in this system on addition of Zn. As a consequence, the tetragonal diluted magnetic semiconductor Zn12xMnxGa2Se4 series exhibits an order-disorder phase transition...

Crystals of BPI and BP2 blue phases exhibit different crystalline structures un~ der sufficiently high electric field. When the dielectric anisotropy is positive, the same tetragonal phase, called BPX, has been observed when the field is applied, either along a two-fold axis of the BP1 phase, or along a four~fold axis of the BP2 phase. With the help of the geometrical models of cubic blue phase...

We analyze the nature of the phase transition from a smectic stripe phase to a tetragonal phase predicted in analytic studies by Abanov et al. @Phys. Rev. B 51, 1023 ~1995!# and observed in experiments on ultrathin magnetic films by Vaterlaus et al. @Phys. Rev. Lett. 84, 2247 ~2000!#. At variance with existent numerical evidence, we show results of Monte Carlo simulations on a two-dimensional m...

The magnetic phase diagram in a single crystal of copper metaborate CuB2O4 in a magnetic field parallel to a tetragonal axis c has been investigated. From the resonant, magnetic and magnetostrictive data the phase diagram of CuB2O4 on a plane “temperature magnetic field” is constructed. The magnetic incommensuratecommensurate phase transition is caused by the saturation of weak subsystem of cop...

Lithium nitride hydride, Li₄NH, was synthesised from lithium nitride and lithium hydride over minute timescales, using microwave synthesis methods in the solid state for the first time. The structure of the microwave-synthesised powders was confirmed by powder X-ray diffraction [tetragonal space group I4₁/a; a = 4.8864(1) Å, c = 9.9183(2) Å] and the nitride hydride reacts with moist air under a...