Electronic Supplementary Information

Piezoelectric power generation of vertically aligned lead-free

(K,Na)NbO3 nanorod arrays

Pil Gu Kang,a Byung Kil Yun,a Kil Dong Sung,a Tae Kwon Lee,a Minbaek Lee,a Nuri Lee,b

Seol Hee Oh,b William Jo,b Hae Jin Seog,c Chang Won Ahn,c Ill Won Kimc and Jong Hoon

Jung*a

a Department of physics, Inha University, Incheon 402-751, Republic of Korea. Fax:+82-32-

872-7562; Tel:+82-32-860-7659; E-mail: jhjung@inha.ac.kr

b Department of physics, Ewha Womans University, Seoul 120-750, Republic of Korea.

c Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan,

Ulsan 680-749, Republic of Korea.

Electronic Supplementary Material (ESI) for RSC Advances.This journal is © The Royal Society of Chemistry 2014

Fig. S1 Effects of seed layer and substrate on the morphology and phase of the KNN NR

arrays. SEM images of KNN nanoplates (a) grown on a SRO/STO substrate without a seed

layer and (b) grown without a SRO/STO substrate. (c) XRD pattern of KNN nanoplates

grown without a SRO/STO substrate. The pattern can be indexed by two phases, i.e.,

orthorhombic and monoclinic structures.

Fig. S2 Effect of the KOH/NaOH mole ratio on the morphology of KNN NR arrays. SEM

images of (a) top and (b) 45° tilt views for KOH/NaOH = 4.5, and those of (c) top and (d) 45°

tilt views for KOH/NaOH = 4.0.

Fig. S3 Piezoelectric power measurement system at elevated temperature; pushing machine,

force gauge, custom-designed heater, and K-type thermocouple. Enlarged view is shown for

KNN NR-array based NG on custom-designed heater.

Fig. S4 Polarity reversal test of the piezoelectric signal. Output voltage and current for

forward polarity (a,c) and reverse polarity (b,d). The forward (reverse) polarity corresponds

to the connection of the positive (negative) and negative (positive) electrode of the device to

the positive and negative probe of the volt/current meter, respectively. For all experiments,

the force and frequency were set to 1 kgf and 1 Hz, respectively.

Fig. S5 Long-term durability of the KNN NR array-based NG at 20 oC. Open-circuit voltage

and closed-circuit current (a) at the initial stage, and after (b) 104 and (c) 105 cycles of 1 kgf

compressive force at a frequency of 1 Hz.

Fig. S6 Frequency dependence of the piezoelectric power generation. Open-circuit voltage

and closed-circuit current as a function of frequency. For all experiments, the force was set to

1 kgf.

Fig. S7 Performance of the KNN NR array-based NG with Pt/Si top electrode at elevated

temperatures. Open-circuit voltage and closed-circuit current at (a) 20, (b) 70, and (c) 100 oC.

For all experiments, the compressive force and frequency were set to 1 kgf and 1 Hz,

respectively.