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Growth and characterization of undoped and Mn-doped lead-free piezoelectric single crystals 0.80Na0.5Bi0.5TiO3-0.20K0.5Bi0.5TiO3

Anandha Babu Govindan 1Indranil Bhaumik 2Ganesamoorthy Sarveswaran 3Ramasamy Perumalsamy 1Gupta P K 2Muthu Raja Arumugam 1

1. SSN College Of Engineering (SSNCE), Kalavakkam, chennai 603110, India
2. Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology (RRCAT), Indore 452013, India
3. X ray Crystallography and Crystal Growth Section, Condensed Matter Physics Division, Material Science Group, IGCAR (IGCAR), Kalpakkam, Tamil Nadu, Chennai 603 102, India


Sodium bismuth titanate, Na0.5Bi0.5TiO3 (NBT)-based solid solutions are considered to be an excellent candidate as lead-free piezoelectric materials, as they have strong room temperature ferroelectricity with high Curie temperature. For unmodified NBT a great deal of difficulties have been experienced in poling because of its high coercive field (Ec=73 kV/cm).

Recently, some modifications of NBT ceramics by forming solid solution with BaTiO3, SrTiO3, NaNbO3, BiFeO3, La2O3, and K0.5Bi0.5TiO3(KBT) have been found to be helpful in the poling process. (1-x)NBT–xKBT system exhibits rhombohedral–tetragonal morphotropic phase boundary (MPB) in the vicinity of x =0.16-0.20. Also, introducing small amount of dopants, such as MnO2, Sb2O3 and Nb2O5 into (1-x)NBT–xKBT based ceramics can greatly improve the piezoelectric properties. However, no investigation has been carried out on doped (1-x)NBT–xKBT single crystals yet. So it is of interest to investigate the effects of doping in 0.80Na0.5Bi0.5TiO3–0.20K0.5Bi0.5TiO3 (0.80NBT-0.20KBT) single crystal for seeking high preference lead-free piezoelectric materials. Pure 0.80Na0.5Bi0.5TiO3–0.20K0.5Bi0.5TiO3 and 1 wt.% Mn-doped 0.80NBT-0.20KBT lead-free piezoelectric single crystals with tetragonal structure were grown by the flux growth method. The crystal structure and lattice parameter of the grown crystal was assessed by Powder X–ray diffraction (PXRD) and the lattice strain (η) has been calculated by using Hall-Williamson relation. The temperature dependence of dielectric constant and loss were investigated in the grown crystals. Two dielectric peaks corresponding to depolarization temperature (Td) and transition temperature (Tc) appeared in curves of dielectric permittivity vs. temperature for the pure 0.80NBT-0.20KBT single crystal. Compared to pure 0.80NBT-0.20KBT single crystal, Mn-doping restrained the transition of ferroelectric phase to antiferroelectric phase. Fitting of the experimental data to a modified Curie-Weiss equation indicates the occurrence of relaxor likes phase transition in grown crystals. The impedance studies have been carried out on Mn doped 0.80NBT-0.20KBT single crystal.


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Related papers

Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 6, by Anandha Babu Govindan
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-03-28 12:25
Revised:   2013-03-31 18:24