Search

Sr5LaTi3Nb1O30 ceramic was prepared by the conventional high temperature solid-state reaction route. The sintered samples were characterized by X-ray diffraction, scanning electron microscopy (SEM), differential thermal calorimetry (DSC) and dielectric measurements. The results show Sr5LaTi3Nb7O30 belongs to paraelectric phase of filled tetragonal TB structure at room temperature, and undergoes a diffuse phase transition in the temperature range of−54-34°C. And Sr5LaTi3Nb7O30 ceramic shows a high dielectric constant of 479 with a low dielectric loss of 0.005 at 1 MHz. In comparison with Ba-based ceramics with TB structure, the temperature coefficients of the dielectric constant (τe) is significantly reduced.

Nonpolar a-plane ZnO film was successfully grown on (302)γ-LiAlO2 substrate by pulsed laser deposition. The temperature of substrate was 500℃, the film was pure nonpolar a-plane ZnO. The FWHM of the peak of near band emission in the PL spectrum was found to be only 115 meV. Both polarized transmission spectra and polarized Raman spectra revealed the in-plane anisotropy of the nonpolar ZnO film by the shift of absorption edge and the change of intensity of Raman E2 mode.

Nonpolar a-plane (1120) ZnO films were successfully grown on (302) γ-LiAlO2 substrate by pulsed laser deposition. When the temperature of the substrate was 350℃, the film was mix-oriented(a and c) with a wide distribution of crystal grain size, and the c-plane ZnO was dominant. When the temperature of the substrate was 500℃, pure (1120) ZnO film was formed，with the FWHM of ZnO (1120) rocking curve ～0.65° and the grain size distribution narrowed. Its in-plane anisotropy was demonstrated by polarized transmission spectrum. The FWHM of the peak of near band emission in the PL spectra was found to be only 105meV for the sample with substrate temperature of 650℃，indicating the large size and uniform distribution of crystal grains which was also confirmed by AFM.

The structure of novel LiAlO2 crystal with Ti concentration of 0.2 at% was studied by measuring the absorption, luminescence and IR spectra. It was found that the crystal has the 196nm typical quarivalent Ti absorption peak, and also the 384nm typical quarivalent Ti emission peak when excited by 235nm light. A color-center model successfully explains the four small peaks in the range of 660—820nm, which disappeared when the samples were annealed in air or Li-rich atmosphere. Compared to the pure LiAlO2, we can find that the intensity and situation of ［LiO4］ are unchanged. Combined with the ICP results, we can count the number of Li vacancies to be about 5.5×1020 for the Ti: LiAlO2 with dimensions of 50mm×1mm.