To carry out this process, heaters with Pt paste as the electrodes were fabricated. The length of the heating area among the electrodes was 35 to 40 mm. The thin film heaters were placed in an ultrahigh-vacuum chamber (approximately 10–7 Pa). Heating power was supplied by a DC constant-voltage source. The heating temperature inside the crucible was measured by inserting an Alumel-chromel thermocouple into the crucible filled with alumina powder (approximately 0.3 μm grain size). Resistance–temperature (R–T) characteristics of heaters were calculated using these measured values.