J Mater Sci(2006)41:7425-7436 10.14(17.5 and 12.7 from the basal plane, respec- degree of crystallographic alignment initially increases tively), also appear stronger in the platelet-containing with increasing platelet content but eventually reaches samples than in the green body or the platelet-free a maximum due to increasing interference between sample. The results confirm that large volume fractions adjacent platelets as they rotate into the plane of the of strong c-axis textured material are formed in sin- tape during tape-casting. Interference between neigh tered platelet-containing samples. Diffraction data boring platelets is also the probable cause of the lower from samples with different initial platelet contents densification at high platelet contents. were compared with the diffraction data from a In traditional texture determination by X-ray dif platelet-free, random sample. The MRD for each fraction, large numbers of grains are sampled simul reflection was calculated and fitted to a March-Dollase taneously and no information is available regarding the model function Phkl(n), and is shown as a function of n crystal location responsible for individual X-ray in Fig 5a. The parameter r in the March-Dollase reflections. Local grain orientation cannot be identified function and the oriented volume fraction calculated by the X-ray method. Transmission electron micros- from Eq 5 are plotted as a function of n in Fig 5b, copy (TEM) is capable of providing diffraction data from which the smallest r value and the highest from grains down to 10 nm diameter with an angular ented volume fraction are seen to correspond to precision, in convergent beam diffraction, as high as initial platelet fraction of 9.1 vol %. In effect, 0.1. However, tEM specimens must be electron 00.12 geen body (9. tvo 91v0% ▲--24w ::48vc% m丰→才 Sintered (9.1 vol%) Angle from basal plane(degree (b) Sintered(4.8 yol/) 鲁一 Chemed voLme factor;% Mrch-oclase Parameter 0.8 6 AA人A~人 40 04 0.2 5 Initial platelet content (vol%) A△人 ultiple of random distribution (MRD) fo flections from textured alumina(TA) samples itial platelet contents, together with the March- Dollase function fitting:(b)the March-Dollase parameter r and Fig 4 XRD patterns for green and sintered alumina samples the oriented volume fractions for TA samples as a function the with different initial seed platelet content initial platelet content 2 Springer10.14 (17.5 and 12.7 from the basal plane, respec￾tively), also appear stronger in the platelet-containing samples than in the green body or the platelet-free sample. The results confirm that large volume fractions of strong c-axis textured material are formed in sin￾tered platelet-containing samples. Diffraction data from samples with different initial platelet contents were compared with the diffraction data from a platelet-free, random sample. The MRD for each reflection was calculated and fitted to a March–Dollase model function Phkl(g), and is shown as a function of g in Fig. 5a. The parameter r in the March–Dollase function and the oriented volume fraction calculated from Eq. 5 are plotted as a function of g in Fig. 5b, from which the smallest r value and the highest ori￾ented volume fraction are seen to correspond to an initial platelet fraction of 9.1 vol%. In effect, the degree of crystallographic alignment initially increases with increasing platelet content but eventually reaches a maximum due to increasing interference between adjacent platelets as they rotate into the plane of the tape during tape-casting. Interference between neigh￾boring platelets is also the probable cause of the lower densification at high platelet contents. In traditional texture determination by X-ray dif￾fraction, large numbers of grains are sampled simul￾taneously and no information is available regarding the crystal location responsible for individual X-ray reflections. Local grain orientation cannot be identified by the X-ray method. Transmission electron micros￾copy (TEM) is capable of providing diffraction data from grains down to 10 nm diameter with an angular precision, in convergent beam diffraction, as high as 0.1. However, TEM specimens must be electron Fig. 4 XRD patterns for green and sintered alumina samples with different initial seed platelet contents Fig. 5 (a) The multiple of random distribution (MRD) for observed (hkl) reflections from textured alumina (TA) samples with different initial platelet contents, together with the March– Dollase function fitting; (b) the March–Dollase parameter r and the oriented volume fractions for TA samples as a function the initial platelet content 7430 J Mater Sci (2006) 41:7425–7436 123