La 1+ x Sr 1– x Ga 3 O 7–δ Melilite‐Type Ceramics ‐ Preparation, Composition, and Structure

Ceramic samples of the melilite‐type La 1+ x Sr 1– x Ga 3 O 7–δ ( x =−0.15 to 0.60) compound were prepared by conventional ceramic processing. Sintering characteristics and microstructural evolution were studied. A phase diagram study was performed to establish the solid solubility limits as a function of the La:Sr ratio. Structural investigations of the Dalton composition as well as strontium‐ and lanthanum‐rich samples entailed X‐ray, neutron, and electron diffraction techniques at ambient and elevated temperatures. The homogeneity region was remarkably broad ( x =−0.15 to 0.60) with no changes in space group observed. A small shrinkage of the unit cell was found with increased lanthanum content. Phase transitions at ambient and intermediate temperatures did not occur.