Dielectric permittivity and Cr3+ impurity ion probe luminescence in SrTiO3 sol–gel ceramics

Synthesis of SrTiO3 Nanopowder by Sol-Gel-Hydrothemal Method for Gas Sensing Application

“…Therefore, the ability to tune the size and shape of ST particles is significant for fundamental studies as well as for the preparation of ceramics and composite materials with tailored properties. There were many synthesis methods applied to prepare pure and doped ST, including solid-state reaction [16], solgel method [17,18], micro-emulsion method [19], hydrothermal synthesis [20][21][22][23], and the polymeric precursor method [24][25][26]. Recently, controlled homogeneity of the precursor gel in the synthesis of ST nanoparticles by an epoxide-assisted sol-gel route was reported by Cui et al [27].…”

Luminescent impurity ion probe and low temperature phase of SrTiO3 nanoparticles

“…7,8 The unusual 'dielectric related' temperature behaviour of the average position of the zero-phonon R-lines of photoluminescence of octahedral Cr 3z centres, controlled by their interaction with the TO soft phonon mode, makes it possible to use Cr 3z ions as a luminescent probe in phase transition and related phenomena studies in the highly polarisable perovskitetype ABO 3 oxides with TO soft phonon modes, as was previously successively proven on the series of chromium doped materials, such as Sr 12x Ca x TiO 3 crystals 9 or SrTiO 3 /Cr sol-gel ceramics, with an average grain size of about 24 mm. 10 The temperature dependence of the position of the R-lines depends on the phase transition character. For example, in Sr 12x Ca x TiO 3 , where the low temperature displacive ferroelectric phase transition occurs 3 for 0?0018(x(0?016, a distinct local minimum in the temperature dependence of the average position of the Cr 3z emission R-lines was observed in the vicinity of the phase transition 9 because, upon cooling, TO 1 phonon mode softens above and stiffens below the ferroelectric phase transition temperature T c .…”

High dielectric constant and tunability of strontium titanate ceramics modified by chromium doping

“…Moreover, the radius of Cr cations (usually stable as a trivalent ion (Cr 3+ ) in the 3d 3 high-spin configuration (S = 3/2)) in octahedral coordination is close to that of Ti 4+ [20] and there are several publications in which a Cr 3+ dopant was reported to occupy Ti sites in SrTiO 3 . These works describe the modification of the conductivity [24], magnetoresistance [25] and ferromagnetism [26], the induction of photoluminescence [27] and the introduction of spin markers for electron spin resonance characterization [28] in ST-based materials. Currently, Cr-doped ST is attracting scientific and technical interest because it exhibits also an insulator-to-conductor behaviour transition with a resistive memory effect, with possible applications for nonvolatile random-access memories [29].…”