Synthesis, crystal growth and second harmonic generation properties of trivalent rare-earth-doped non-linear tungsten–bronze-type structure Ba 2Na 1−3 xRE xNb 5O 15 (RE=Sc, Y, La, Gd, Yb and Lu)

Abstract

A new compound filled tungsten–bronze-type structure Ba 2Na 1−3 x RE x Nb 5O 15 (trivalent rare-earth ions: RE 3+=Sc 3+, Y 3+, La 3+, Gd 3+, Yb 3+ and Lu 3+, with x=0.02) has been prepared by selecting RE 3+ ions without any absorption in the visible range. The effect of rare-earth addition on micro-twin formation, that is to say, tetragonal–orthorhombic ferroelastic phase transition in barium sodium niobate was investigated and micro-twin formation could be suppressed by doping of smaller RE 3+ ions such as Yb 3+ and Lu 3+. All the samples exhibit an intense second harmonic generation signal under tunable IR pumping laser source, due to both the high values of the non-linear optical coefficients and the absence of absorption of additional RE ions in the visible range.