Ftir pellet dies

Powder compaction was performed via cold uniaxial pressing resulting in a disk‐shaped specimen. A defined mass of powder (m = 150 ± 10 mg) was transferred into the cavity (d = 13 mm) of a compaction tool (FTIR Pellet Dies, Specac) and hydraulically consolidated by applying the pressure of 74 MPa for 1 min to obtain green compacts. We performed thermal treatment using a muffle furnace (Nabertherm LT 5/12). This furnace provides the possibility to control the sintering atmosphere by introducing a continuous gas flow. The green compact was placed in the muffle furnace inside an Al₂O₃ sample container and heated up to 1173 K. This step was performed under continuous oxygen flow and with a heating rate of 10 K/min. The oxygen flow at atmospheric pressure is provided during the heating to purify the sample from the adsorbed species, which arise from processing in the ambient atmosphere. After reaching 1173 K and dwelling for 10 min, the oxygen flow was replaced by continuous argon flow, and the sample was heated at 10 K/min to the final temperature of 1373 K. This temperature was kept constant for 2.5 h before cooling down to room temperature.

Powder compaction was performed via
cold uniaxial pressing resulting in a regular disk-shaped specimen.
A defined mass of powder (m = 150 ± 10 mg) was
transferred into the cavity (d = 13 mm) of a compaction
tool (FTIR Pellet Dies, Specac) and uniaxially compressed with a hydraulic
press (Atlas manual hydraulic press 15T, Specac) under an applied
pressure between p = 1 MPa and 74 MPa that was dwelled for 1 min to
obtain green compacts in a controlled and reproducible way. To minimize
the amount of water adsorption, powder transfer and compaction was
performed inside glovebags filled with Ar at room temperature.

Compaction
of FSP-grown nanocrystals was performed by transferring a defined
mass of the powder (m = 150 ± 10 mg) into the
cavity (d = 13 mm) of a compaction tool (FTIR Pellet
Dies, Specac) followed by uniaxial compression (p = 74 MPa, t = 1 min) with a hydraulic press (Atlas
Manual Hydraulic Press 15T, Specac). Disk-shaped green bodies are
reproducibly obtained in this way, whereby porosities Φ of green and sintered compacts can be calculated geometrically through
the weight and volume of the pellets via eq 1
To account for the volume
fraction
of admixed metal ions in the theoretical density values of Me_xMg_1–xO
systems, we applied the rule of mixture (see the Supporting Information).
Pressureless sintering
of the green bodies was performed within
a horizontally operated high-temperature ceramic tube furnace (Nabertherm
RHTH80-300/16). Disk-shaped green bodies were sandwiched between alumina
plates to guarantee smooth ceramic surfaces after sintering and placed
on an alumina crucible in the middle of the tube furnace. Synthesis-related
carbonaceous species become eliminated via application of a continuous
flow of molecular oxygen [Q(O₂) = 50 mL
min^–1] during the sintering protocol. Specimens
were heated with 5 K min^–1 to the final temperature
of 1373 K, dwelled at this temperature for 2.5 h, and then the furnace
cooled to room temperature.