o 2 to 960 u00b0 970 u00b0 c a vacuum was quickly drawn and then the pressure was stabilized at 2 torr of o 2 the pellets were then held at temperature for about 8 5 h solidification was accomplished by decreasing the vacuum in stages and for most pellets the po 2 was doubled periodically the time to reach atmospheric pressure ranged from 0 2 to 8 h once the pellets were solidified isothermally the pellets were cooled to 450 u00b0 c and were given a final anneal in o 2 at 450 u00b0 c the resulting pellets were examined by scanning electron microscopy sem and are shown in fig3 the results for x ray diffraction xrd for the pellet solidified over 8 h of isothermal treatment are shown in fig4 surface resistance was examined at 2 84 ghz measurements were made with a tio 2 dielectric resonator operated in the te 011 mode and the results are shown in fig6 these heat treatments induced melting and resolidification of surface layers only the pellets exhibited very little change in size or shape in 2 torr of o 2 0 5 h at 960 u00b0 970 u00b0 c the result was a molten layer of lt 1 mm sem revealed that pellets for which the po 2 was raised to atmospheric pressure quickly 0 2 h consisted of large grains that were often oriented substantially randomly voids and regions of second phases were present where these grains met in contrast for pellets in which 8 h was spent to increase the po 2 to atmospheric pressure the grains exhibited much better alignment with the c axes of the grains perpendicular to the pellet surface and less second phase was present see fig4 x ray.