Electrical Conduction Behavior of La_1+xSr_1−xGa₃O_7–δ Melilite‐Type Ceramics

Abstract

Ceramics of the melilite‐type compound La1+xSr1−xGa3O7−δ were prepared by conventional ceramic processing. Samples prepared represented the entire homogeneity region of the phase (i.e., x=−0.15 to 0.60). Electrochemical characterization under variable temperature and atmospheric conditions in the vicinity of air entailed four‐point direct‐current conductivity measurements and electromotive force measurements. La1+xSr1−xGa3O7−δ samples exhibited a p‐type behavior with generally increased conductivity with increased substitution of lanthanum for strontium, which reached a saturation value of ∼10−1 S·cm−1 at 950°C.

Layered LaSrGa3O7‐Based Oxide‐Ion Conductors: Cooperative Transport Mechanisms and Flexible Structures

“…[14][15][16] This compound becomes an interstitial oxide ion conductor when excess oxygen is introduced within the structure by modifying the cation stoichiometry to La 1+x Sr 1-x Ga 3 O 7+δ , where x ≈ 0.5. In particular, ionic conductivity values of 0.02 to 0.1 Scm -1 are obtained in the temperature range 600 to 900°C for La 1.54 Sr 0.46 Ga 3 O 7.27 .…”

Vaporization and Diffusion Studies on the Stability of Doped Lanthanum Gallates

“…After 200 h the Ga vaporization rate for this composition is highest (see Figure 12). A similar high vaporization rate of Ga was ob- -10 -5 [53,5] * calculated using the cation radii r(La3+) = 106 pm, r(Sr2+) = 110 pm, r(Ga3+) = 62 pm and r (Mg 2+ ) = 65 pm reported in [6]. Concerning the influence of doping elements on the Ga vaporization (Figures 12 and 13) one can conclude that for most of the Fe-doped lanthanum gallates investigated, the total amount of released Ga is less than for the standard material LSGM-2020, Figure 13.…”

Electrochemical Investigation of LSGMC-Composite Cathodes on LSGM-Substrate

“…XRD patterns have been identified as the desired perovskite phase with the cubic structure (space group Pm3m) for LSGM (23,24) and LSGMC (25). The secondary phases of LaSrGa 3 O 7 (JCPDS # 45-0637) and LaSrGaO 4 (# 80-1806) were present in both LSGM and LSGMC samples at the low calcination temperature.…”

“…Neither of the secondary phases is desirable. LaSrGaO 4 has been shown to be electrically insulating while the LaSrGa 3 O 7 phase was reported to have very low electrical conductivity (23). Since Co has been known to improve the sinterability of perovskites, LSGMC specimens demonstrated relatively less secondary phases at 900ºC and 1400ºC as compared to the LSGM.…”