For each sample a powder and a tran

For each sample a powder and a transient liquid were manually mixed with an agate mortar and pestle for 2–5 min. The mixture was then poured into a 12.6 or 13 mm diameter stainless steel die and uniaxially pressed using a Carver Model M press or a device composed of a) an ENERPAC press able to automatically maintain the pressure constant with the help of an electric hydraulic pump, b) a dilatometer with a Keyence GT2-H32 Digital Contact Sensor [30]. The mixture was first pressed under the sintering pressure at room temperature for 10 min to allow further particle rearrangement [31], then the temperature was increased to the sintering temperature with a 20
C min-1 average heating rate. The mixture was then maintained in the die at sintering temperature for a certain time and the pressure was manually or automatically readjusted when shrinkage was observed. The sintering conditions of materials presented in this paper are summarized in Supplementary Data, Table S1.