Structural, dynamical, optical and magnetic properties and of ATiO3 (A=Pb, Co) titanates synthesized by solid state reaction

ATiO3 ceramic materials represent a wide class of important materials for technological applications and some compositions have been exhaustively studied, mainly those with perovskite structure with A = Ba, Pb, Sr, Ca.... [ view full abstract ]

ATiO₃ ceramic materials represent a wide class of important materials for technological applications and some compositions have been exhaustively studied, mainly those with perovskite structure with A = Ba, Pb, Sr, Ca. However, in the case of A = Co, Ni, Mg (or others transition elements), the most stable structure is ilmenite. While the PbTiO₃ perovskite present electric order –ferroelectricity-, the CoTiO₃ ilmenite present magnetic order, it is antiferromagnetic below ~ 30 K. In the present work, it was studied the complete serie of Pb_xCo_1-xTiO₃ with x ranging from 0.0 to 1.0 using X-ray diffraction, Raman scattering, optical absorption and magnetic susceptibility. The atomic substitution led to a variety of interesting changes in the physical properties:

1- for x < 2.0, there is the formation of a solid solution while for x > 0.2 there is the formation of a composite;

2- the unit cell volume is reduced to the minimum value at x = 0.4 while the Curie temperature is reduced by 50 K;

3- the optical energy band gap is reduced continuously from ~ 3.1 for x = 0.0 to 2.2 eV for x = 1.0;

4- only changing the atomic substitution level, the material starts from ferroelectric and diamagnetic for x = 0.0, goes to ferroelectric and paraelectric for 0.0 < x < 0.2, than to ferroelectric and antiferromagnetic for 0.2 < x < 0.96 and finally non-ferroelectric and antiferromagnetic for x = 1.0.