[en] Published in summary form only

[en] The effect of film thickness on the dielectric constant and d.c. breakdown field strength of electron beam evaporated lanthanum sesquioxide thin films in the thickness range of 270-2000 A has been studied. The dielectric constant slowly increases from 8 to 18 with film thickness and becomes constant for thicker films (> 900 A). The breakdown field strength decreases for thicker films (> 900 A) but attains saturation for thinner films (> 900 A). (M.G.B.)

[en] Molar heat capacity of La_2Ti_2O_7(s) was determined using differential scanning calorimeter. The dependence of molar heat capacity with temperature for La_2Ti_2O_7(s) can be given in polynomial form as,C"o_p_,_m_L_a__2_T_i__2_O__7_(_s_) (J.mol"-"1.K"-"1) ± 0.33 = 243.13 + 0.03T-8.25 x 10"6T"-"2 (700 K≤T/K≤900 K ). From this data, H"o(T)-H"o(298.15), S"o(T)-S"o(298.15) and Gibb's free energy function were evaluated. (author)

[en] Nanoindentation measurements in tetragonal lead zirconate-titanate (PZT) ceramics doped with 0.8 mol% of La₂O₃ with a composition close to the morphotropic phase boundary (MPB) were performed using indenters with different tip radii. The elastic modulus was independent of indenter size but varied as expected with the Zr/Ti ratio of the samples. On the other hand, the calculated mean pressure remained constant for each indenter above the first pop-in, also varying with the Zr/Ti ratio, but was in all samples clearly dependent on the indenter radius. Indentation size effect (ISE) in tetragonal PZT was partially explained by the concept of 'geometrically necessary dislocations'. However, the experimental data also indicate that the actual ISE model needs to be slightly extended to include the ferroelastic domain switching contribution

[en] Charge-order driven magnetic ferroelectricity is shown to occur in several rare earth manganates of the general formula, Ln_1-xA_xMnO₃ (Ln rare earth, A = alkaline earth). Charge-ordered manganates exhibit dielectric constant anomalies around the charge-ordering or the antiferromagnetic transition temperature. Magnetic fields have a marked effect on the dielectric properties of these compounds, indicating the presence of coupling between the magnetic and electrical order parameters. Magneto-dielectric properties are retained in small particles of the manganates. The observation of magneto-ferroelectricity in these manganates is in accordance with theoretical predictions. (author)

[en] The influence of mechanical activation of the powder mixture used to obtain the high-perfomance cathode for accelerating engineering with the SHS-method has been explored. The mechanically processed mixtures have been morphologically analyzed. The optimal modes of mechanical activation have been determined for the mixture. (paper)

[en] Rare earth Er"3"+/Yb"3"+ codoped La_2O_3 with Li"+ upconverting nanoparticles are successfully synthesized with the expansion of combustion technique. There are marvelous energy level manifolds in the near-infrared, visible and ultraviolet spectral ranges because of the exclusive electron arrangement of their ions. The Upconversion nanoparticles, however, only an insufficient number of capable upconversion excitation and emission are produced due to sensitizer Yb"3"+ and activator Er"3"+ ions thus the purpose of UC materials proclaims on the sensing, fingerprint detection and bioimaging by using the upconversion luminescence. Lately, huge numbers of workers have been ongoing to meeting point of upconversion optical possessions and mounting of upconversion nanoparticles by exciting the atoms. Under this communication, authors offer a complete examination on recent application that challenges to the practitioners. (author)

[en] The dielectric breakdown in La²O³ films of thickness 40-400 A incorporated in capacitors is reported. The experimental results were analysed in the light of Forlani and Minnaja's theory of ionization avalanche breakdown. The dielectric breakdown strength was found to be a power function of thickness, in essential agreement with the theory of Forlani and Minnaja. Furthermore, these films are amorphous and have high breakdown fields (about 10 MV cm^-₁). (Auth.)

No abstract available

[en] Three kinds of lanthanum oxides (La_2O_3) were synthesized from different methods and used as a catalyst in the transesterification of dimethyl carbonate (DMC) with glycerol for the synthesis of glycerol carbonate (GLC). Lanthanum oxide synthesized using a surfactant (S-La) showed a much higher GLC yield of 89.9% compared to other lanthanum oxides synthesized by calcination (C-La) and precipitation (P-La) at the reaction conditions of 90 °C, DMC/glycerol = 2, and catalyst/glycerol = 5 wt %. The best catalyst was obtained when the surfactant/La weight ratio was 12. XRD study revealed that S-La has large amount of monoclinic and hexagonal La_2O_2CO_3 phases, which are assumed as active sites of the catalyst for the reaction