Hello,

if the surface of samples is the same during XRD characterisation (small sample might give an exagerated contribution at high angle), i guess this comes from the pressure applied during pressing. This pressure would certainly affect more the surface rather than the bulk. So any particular shape of particles (plates) might be accentuated in surface.

Another possibility would be reaction with support but in this case it would affect only one side.

I do not know. Funny thing anyway.

Really not sure it helps.

Guilhem

To follow my argument, it would be useful to check the relative stability among REAlO3. Also it would be nice to check the original particle shape as a function of RE.

i am really impressed by the La-doped sample.

Dear Dmitry,

Try to correlate melting points of the doping oxides with sintering temperature.

Dopants such as Sm can reduce sintering temperature and enhance the grain growth compared with Y, because its melting point is slightly lower. It is also found that In can reduce sintering temperature down to 1300 C, melting point of In2O3 was significantly lower than that of Y2O3. This observation may be useful to explain the degree of preferential orientation at the surface when you compare these dopants, as well as their radius size. 

Also, check the solubility of each dopant in the system BaCeO3-BaZrO3.

Otherwise, you may avoid preferential orientation by introducing sandwich-like configuration of three pellets, whereas the one on the top and other at the bottom could be much thinner and serve to protect the inner one. However, it is interesting to determine if the preferential orientation can influence the electrical properties of the electrolytes.

Best regards,

Aleksandar

One thing it is sure that the aggregates of particles having almost  quasi-spherical (equiaxed grains) shape can't show any texture with or without the external mechanical force such as using a razor edge to smear out the powder particle lying on glass substrate along one direction.  If the particles would be elongated in shape that sample prepared by above technique shows texture definitely by experience.

If the powder samples prepared by the method described by Dmitry, which are first pressed hydrostatically into pellets then sintered at high temperature would show ordering by grain sliding and rotation driven by surface and grain boundary diffusion if the individual crystalline grains would have quasi-tetragonal structure.  But the selection  of final direction of  the alignment of grains would  be  either random in the plane of the pellet or it is perpendicular to plane.  The effect   of  LN  elements on the texture arises due the fact that these elements probably  occupies certain interstitial sites in lattice unit cell, which increases the tetragonality. That  is the case for the  Martensite, which is supersaturated ferrite (tetragonal) and carbon atoms mostly takes octahedral sites along the  c- axis, even though structure stable ferrite is BCC.  

Dear Nader, probably your guess is OK.  The formation of  a texture in doped samples  according to  Dmitry is confined only to the surface layer but not the bulk region. Since there is no external stress applied during the sintering one can't use the grain sliding and rotation model as we employed extensively in  super plasticity to explain the texture formation. My guess is that here some short of recrystallization taking place by nucleation and growth [similar to --the metals and alloys, where the driving force is just to  reduce to stored  stain energy associated with the dislocations, inclinations and low angle  dislocation boundaries]   where the surface diffusion driven by  capillary forces activated by the  high sintering temperatures  plays predominate role in  reduction of Global Helmholtz free energy.